PDA

View Full Version : 447 / 503 interchangability



profqwerty - n/a
20-Jan-08, 06:59 PM
Right. I have brought back the 503, it runs smoothly and is in nice condition. He also gave me the CHT guages + dials so that'll be useful http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif .



Anyway it is actually a free air version with cowelings to duct air to the fins from the prop.



Is it possible to put the 447 fan onto it? Or perhaps it is better to keep as a free-air version (more power for the the fan?)?



If left free-air, what do people do to keep it cool?



What about taking a duct off of the plenum to make sure there's at least some air over it?



Toby

Jamie Lewendon - n/a
20-Jan-08, 08:36 PM
The 447 fan cowling kit is smaller than the 503. Whether you can get away with leaving it free air, will depend on how low in the craft you have it, and how far from the fan. If you are going to run it Free ar, you NEED EGT'S, otherwise you will end up with the same problem as your 503. They aren't mega expensive and well worth it. In most cases the fan will draw enough air over the engine to keep it cool.



You will also find that the mounting holes underneath are irritatingly slightly different between the 2 types.



Other than that, they are very similar indeed. I'm in the Reading area quite often, and would be willing to give the craft a once over if you like, and could scrutineer it for you.



Jamie

Iceman - n/a
21-Jan-08, 04:29 PM
Free air cooled 503's run alot hotter than the fan cooled versions and therefore you need to make sure you have adequate air flow over the engine AND good quality oil. Also you will need to turn the heads 90 degrees.



I have a load of bits and pieces for converting to fan cooled so if you want to go down this route, give me a shout.

sixpackpert - n/a
21-Jan-08, 04:32 PM
If you want reliability then fan cooled all the way. Ours hasn't missed a beat in 3 and a half years (apart from when a spark plug fell out, poor maintenance http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif ).



We certainly haven't noticed the very slight loss of power http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif

jon_curtis - n/a
21-Jan-08, 06:29 PM
this 503 you bought? is it points ignition? twin or single spark?

if you have ended up with a points single spark free air cooled 503, then 600 quid is not that great a deal! also unless its setup right, you gona have the same problem as you did with the 447!



you could have fixed the 447 for what it might cost to convert the 503 to forced air cooled.



did you work out what caused the 447 to fail?



sorry for being unconstructive, but your certainly gona need someone in the know you help setup the 503! (not saying thats me, as i have not used one free air cooled)



hope you get hovering again soon.

team black - n/a
21-Jan-08, 08:05 PM
I think I still have the cooling kit for a 503 if you're interested

profqwerty - n/a
22-Jan-08, 05:29 PM
hmm yeah it is points single spark free air cooled 503. hmpf.



I'm still in two minds about converting it to fan cooled - it certainly would have plenty of air flow from the main fan.



Then there's the cost of a cooling fan. I already have EGT and CHT guages on it!

How much air does it actually need flowing over it?

Could neat ducting provide this from the lift or thrust fans?

jon_curtis - n/a
22-Jan-08, 06:52 PM
it certainly would have plenty of air flow from the main fan.



Then there's the cost of a cooling fan. I already have EGT and CHT guages on it!



How much air does it actually need flowing over it?

Could neat ducting provide this from the lift or thrust fans?






it would not ness have enough airflow from the fan, the further away from the fan the less it will get! you have a flexi coupling dont you? you would have to turn the heads, and i imagine put bigger jets in! but i dont know much about this!



good on the cht end egt, are they duel? one on each cylinder and exhaust port? or a combi gauge? do you have just one gauge or two?

if just one the cylinder with no gauges could be cooking and you not even know!



the cht will not tell you much, it will tell the engine is up to operating temp, but thats gona happen fairly quickly lol, CHT's are slow to reacte.



the egt's are what you wana fit, and preferrable one on each cylinder, these will also help setup the engine! EGT's reacte quickly so will tell of problems quickly!



how much air? a fair bit i would suspect, seeing as the 503 cooling fan spins faster than the crank, alot!

you can, i imagine duct air off the plenum to cool the 503, seen it on some racing craft, but for reliability the cooling fan is a must!



are you wanting to race this thing? its gona need some specific setup as mentioned previous, and as the problem with your 447 sounds like a setup problem, you could be asking for 503 pistons and barrels soon!

i would try and convert to fan cooled if its possible with the engine you have!

sixpackpert - n/a
22-Jan-08, 07:01 PM
Friend of mine ran a tube from the plenum to the cowling to provide the cooling and it worked fine. This method provides a constant amount of air to flow over the engine.



Relying on the fan to cool the engine has varying amounts of success dependant on setup. All I know is that over the years of running a 503 as standard straight out of the box with a cooling fan we have not had an engine failure of any type (granted the engine was brand new to start with). Other competitors have had pistons nipping up every now and then so costing race finishes, and as we know points mean prizes http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

profqwerty - n/a
22-Jan-08, 07:31 PM
EGT and CHT have separate guages that actually look pretty similar.



They're combie guages - two needles one for each cylinder, so one EGT sensor and one CHT sensor per cylinder.



As soon as i can get hold of a cooling fan I'll put it on i think http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

Jeremy - n/a
22-Jan-08, 09:51 PM
Free air cooling works fine as long as you can get about 30 to 40 mph of air velocity over the heads. I've flown with several free-air cooled Rotii and always found them to be fine.



EGT won't tell you the heads are overheating, but will tell you that the mixture is out. At full chat the air cooled Rotii are designed to run rich for better cooling, so the EGT will be cooler than at part throttle (if they are jetted and set up properly).



The very best indicator for cooling system effectiveness is the CHT. Even though it's slow to react it is telling the truth about the actual level of cooling available, the EGT will go up and down like a whore's drawers with changes in throttle, due to the deliberate top end richness. Relying on EGT to measure cooling effectiveness will deceive, as if you're at full chat for a while and think things are getting hot, throttling back will make the temps go up on the gauge (or should do if it's set up properly).



EGT will advise you of a mixture problem that might end up melting a piston, CHT will tell you whether you have a cooling problem that might lead to a seizure. Both are invaluable on a two stroke, in my humble opinion.



Jeremy

profqwerty - n/a
23-Jan-08, 10:05 AM
So if I continuously monitor the guages it might be ok http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif .



How about ducting air from the plenum then?

I could put an inspection hatch in, cut a hole in the lid, then fix a bucket or something to guide air across the cylinders.



If I put a fan on the engine then close off the hole with a new lid.



Any other ideas?

sixpackpert - n/a
23-Jan-08, 10:12 AM
So if I continuously monitor the guages it might be ok http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif .








Trust me, in the middle of a race you won't have time to continuously monitor gauges!



Get the cooling fan put on and get it set up right. What you have to remember is that when a free aircooled engine is in a plane it has constant forward motion pushing air over the heads.



In a craft the engine is being swung around when you turn so not giving it a constant even flow of air over the heads.



Just my 0.02p, now back to work! http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

nickyd - n/a
23-Jan-08, 01:14 PM
Hi Toby,



We run fan cooled and never had any trouble. (although it did nip up due to fuel starvation once)



However, Steve Walsh cained everyone this season and didn't have any fan cooling on..........



If you get it right then it will be quicker because you will have more power to play with. But you GOT to get it right!



We are sticking with the fan cooling this seaon.



It might be worth getting it in and running first, set it up so its running within its limits, have some fun in it then have a think about which way you want to go.





Thats my 1 pence worth http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif



Nick

sixpackpert - n/a
23-Jan-08, 01:29 PM
However, Steve Walsh cained everyone this season and didn't have any fan cooling on..........



Nick




He would have caned everyone with the fan cooling on as well I would have thought, and by having one of the lairy's in there with him! http://hovercraft.org.uk/images/icons/smiley_icons/icon_cry.gif Must try harder, new ideas http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif



In fairness I don't recall it nipping up at any point, but I may be wrong. Can't remember if it was Steve's or Ewan's engine Jamie had his head in at one meeting.



My point is that for the marginal performance increase taking the cooling fan off gives, reliability will suffer. Oh and up until Walshy came along (bless him http://hovercraft.org.uk/images/icons/smiley_icons/icon_mad.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif ) the quickest craft in F503 had a fan cooled engine http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif <font size="1">had to get that one in.[/COLOR] http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

RHudson - n/a
23-Jan-08, 07:08 PM
I've always run free aircooled, however you do need to get the engine as far back as possible and turn the heads (you'll have to trim a little off the heads to get them to fit when turned).

I've raced on 165 front and 170 rear jets and had minimal problems.

If you are using a coupling then its unlikley that you will get the engine far enough back so I would use fan cooling.



Russ Hudson

Jamie Lewendon - n/a
23-Jan-08, 07:23 PM
I've been in lots of engines this season...

The only problem we had with Steves engine was when it fell out at Jakes http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif



jamie

bryan - n/a
23-Jan-08, 07:32 PM
1.If you run a air cooled 503 without the fan the heads must be turned to give free air flow into the thrust fan.On this set up the bottom drive comes straight of the crank making the engine sit back into the thrust fan which helps draw the air through the heads.You are using a centre flex coupling so steer clear of this!

2.I have cooled the engine by using air from the plenum on a intergrated craft in the past. Although i still used the engine shroud without the fan and a 75mm tube.Be warned you are using a twin engine craft so you will not be able to run your 503 for long without your lift running!

3.Rotax have not spent millons getting this motor to run for may hours for us to take the engine fan off and find ourselfs wondering why it just nipped up! If you have no way to monitor your exhust temps i would leave it standard for the time being and have some fun.Just a tip i would put a mesh of sorts over the rotax fan to stop the loss of the odd T shirt or your butt stopping the fan drawing in that cooling air.

Jeremy - n/a
23-Jan-08, 07:44 PM
Does nobody use the free air cooling shroud? This is designed to both direct air into the fins and provide a baffle to slow down some of the air and stop the rear cylinder running hotter than the front one.



It's standard on the free air cooled versions of Rotii used on microlights and avoids needing to muck about turning heads around.



Rotax do sell these engines in a free air cooled version, with a different mag case and no cooling fan tower. although the fan is a good thing, the pulleys do corrode slightly, which can lead to rapid belt wear and sudden cooling fan failure. When this happens in a microlight seizure usually follows pretty quickly, followed by things going a bit quiet............



Jeremy

Iceman - n/a
23-Jan-08, 08:27 PM
The free air cooled shroud fitted by Rotax and the grp versions fitted on a/c such as the AX3 and Thruster rely on ram air from the prop and forward air speed. On a/c such as the Chaser which have the prop behind the engine, cooling is acheived mainly on the forward airspeed, those a/c cannot be run for too long on the ground without overheating issues. This setup in a hovercraft is not advisable as the air flow over the engine approaches from all different angles at different times.



Ken Rigley has a venturi type shroud on his racing 503 to use the low pressure in front of the fan to draw air over the engine. I think if this is setup correctly then it is the best solution for a free air cooled engine in a hovercraft.



I run 3 503's on my corporate craft and these are all fan cooled, it is by far the most reliable method for cooling. It makes maintenance a bit more involved but unless you are doing loads of hours, its a small price to pay. The mesh over the cooling fan cover is highly advisable to prevent the build up of debris inside the engine which can (and has!)caused seizures.



The cooling fan on the 503 absorbs about 2hp which may sound alot but is pretty irrelevent compared to the other losses present in hovercraft.



The bottom line is: go fan cooled, set your carbs up as Rotax specifiy, make sure your timing is spot on, keep fuel and air filters clean, use good oil and make sure your exhasut setup is correct, then you will get many many trouble free hours from your 503.

jon_curtis - n/a
23-Jan-08, 08:32 PM
even a slipping of the belt due to corrosion can lead to ineffective cooling! i had this and found the rear cylinder running hotter!



its important to keep an eye on that belt and pulley!



free air cooled on a microlight? pusher or puller? the later would indeed give plenty of air flow!

profqwerty - n/a
23-Jan-08, 08:42 PM
This one did come with an air scoop that looked a bit home made. It was nothing more than a scoop, but was in a tractor microlight config so would've had the prop air.



Well soon as one comes up nice and low priced I'll put it on! meanwhile got other bits to look at http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Iceman - n/a
23-Jan-08, 08:42 PM
The AX3 uses a free air cooled 503 in a puller arrangement, I don't think there has ever been a cooling issue with this setup.



Chasers uses a pusher setup and can't be run flat out stationary without temps getting a bit high.



Yes, checking the belt is very important, luckily the fan cover unclips easily and regular inspection is easy.

Jeremy - n/a
24-Jan-08, 06:19 AM
My experience of fan cooling has been two in-flight belt failures, so I agree about checking the belt tension regularly. The easy way is to drill a hole in the side of the fan casing, level with the middle of the belt span and big enough to take a biro. The check is to just push a biro through the hole until it touches the belt, then push it to see how much the belt deflects. I've never understood why Rotax don't provide an easy way to check the belt as standard, other than sticking your fingers in the fan hole.



Free air cooling can be very reliable indeed if the shroud is well designed, as there is nothing to go wrong. The US made ones that are "S" shaped are far and away the best on pushers, as the rear-facing outlet very effectively sucks air through the shroud. I can't see why this wouldn't work as well on a hover as it does on a rear engined microlight. You also gain 2 or 3 hp by getting rid of the fan.



Jeremy

sixpackpert - n/a
24-Jan-08, 07:13 AM
I can't see why this wouldn't work as well on a hover as it does on a rear engined microlight. You also gain 2 or 3 hp by getting rid of the fan.



Jeremy




I think this has been answered 2 or 3 times previously in the thread. http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

Jeremy - n/a
24-Jan-08, 05:52 PM
Sorry, as far as I can see no one else has made a reference to the S shaped free air cowls that I know to work well on pushers (and perhaps hovers) at all. I thought the tip might actually help someone.



I can take the hint though, I shall stop posting and go back to ignoring this place once more.

sixpackpert - n/a
24-Jan-08, 06:30 PM
Sorry Jeremy, I didn't mean to upset you, far from it, you make some valid points. Would you have a picture of the cowl that you mention as I (and probably others) haven't come across it.



The main reason I am an advocate of using the cooling fan is that it is IMHO the best way to cool the engine when it is in a hovercraft. Some craft manage to run very well without the cooling fan, but you could take that engine and put it in another hull and find that there is not enough cooling, and you start getting problems.



The big problem with hovercraft is that no-one makes engines specifically for them, so we have to take engines from other applications and make them work in our craft, that's the fun of a build. While microlight engines do seem the ideal and logical engine to use it still takes some handy engineering to make them work properly in our application.



In a microlight or fixed wing you will always be travelling forwards with no obstruction to the air passing over the engine. In a craft the engine is travelling forward one minute, then sideways, then up in the air etc. You also have a driver that is moving around a lot in front of the engine so disturbing the airflow.



That's my view on it and because I am not a fluid dynamics bod I could be talking complete drivel http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif but in my laymans mind that is what is happening. So again Jeremy I apologise but please don't take offence and please post that pic if you can find one. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

jon_curtis - n/a
24-Jan-08, 06:32 PM
thats a bit over the top jeremy!



he might very well have to try this sort thing, as if it was a free air cooled to start with, the castings will be different, and it might be very hard to fit the fan etc.



i can see your point, but however a microlight spend very little time on the ground, the airspeed alone would give more airflow and its colder up there! but perhaps the air at sea level having a greater density would help with cooling? i can imagine not enough to balance out? the airspeed effect.

Iceman - n/a
24-Jan-08, 06:58 PM
Converting 503/447's from free air-cooled to fan-cooled and vice versa is easy and only takes about an hour.

profqwerty - n/a
24-Jan-08, 07:00 PM
I will be taking the engine to David next weekend (can't decide to drive or train it http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif ), to fit a fan he has. This is coming off a points engine so should fit.



I asked Ken about it, and he pointed out that, along with the engine being away from the fan, it is a 1100mm duct so the airflow would be too slow.



I think free-air would be something to look at in the future as as Jeremy says you get a wee bit more power from it http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

jon_curtis - n/a
24-Jan-08, 07:15 PM
Converting 503/447's from free air-cooled to fan-cooled and vice versa is easy and only takes about an hour.




im sure your right david! all i was trying to point out for toby, is that rotax did make several different types of bottom end casting for various applications, everything 503 does not necessarily fit every 503 and he should look into whats require prior to jumping in and spending more money!



however it looks like he is getting help from someone in the know, so no worries http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Mart366 - n/a
24-Jan-08, 07:22 PM
What is the gain in BHP from running free air to forced cooling?



If the gain is massive, then fairplay, go for it.



if the gain is minimal or marginal, then you have to look at the bigger picture. do you want power or reliability.



btw, my 447 is run with a cooling fan





Mart

Iceman - n/a
24-Jan-08, 07:27 PM
You're right about the variations in castings but its only the gearbox end that varies. The triggers on electronic versions mount in the recoil or recoil/fan housing so that needs to be looked out for as well but fortunately on the whole, interchangability on Rotax's is fairly good.

Iceman - n/a
24-Jan-08, 07:30 PM
The 503 cooling fan absorbs about 2hp, so I would guess on a 447 maybe 1.75hp. You could argue that being free air cooled is better all round as you 'recover' that 2hp AND lose some weight but hovercraft are not simple beasts and I doubt if anyone would notice a performance gain by converting.



By the way (opening up another can of worms) how can you have bhp on a hovercraft??? There are no brakes!!!!

sixpackpert - n/a
24-Jan-08, 07:37 PM
Maybe SHP then - Slide Horse Power? http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

Iceman - n/a
24-Jan-08, 07:44 PM
HP is the power generated by the engine and is usually measured at the flywheel, whereas BHP is measured at the wheel and is effectively the power the brakes have to deal with hence the name.



BHP is perhaps more relevant because its the usable power. In a hovercraft we should be interested in FHP, fan hp. And we all know you can never have enough F hp.

sixpackpert - n/a
24-Jan-08, 07:47 PM
There are no brakes!!!!




Oh I don't know how about, how about THP. The best brake I found was a tree! I'll leave you to test the THP of craft though David! http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

Iceman - n/a
24-Jan-08, 07:51 PM
I did that ONCE! And I can declare it is a very effective method!

Don83000 - n/a
25-Jan-08, 01:27 AM
Quote from encyclopaedia just so that all are singing from the same hymn sheet :-



Brake horsepower (bhp) is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components. Thus the prefix "brake" refers to where the power is measured: at the engine's output shaft, as on an engine dynamometer. The actual horsepower delivered to the driving wheels is less. An engine would have to be retested to obtain a rating in another system. The term "brake" refers to the original use of a band brake to measure torque during the test (which is multiplied by the engine RPM and a scaling constant to give horsepower).

team black - n/a
25-Jan-08, 07:19 AM
fahp is the resultant power when an engine of a given power is installed in my hovercraft

keith rhodes - n/a
25-Jan-08, 07:59 PM
what a good string!!! can everyone just take a breath and note the lack of negative comments.

good to see experienced racers giving good honest advice.

thats a credit to the club and this forum

team black - n/a
26-Jan-08, 04:43 PM
I've always believed they were capable of playing nicely http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Vortex - n/a
28-Jan-08, 10:38 PM
Sorry to contradict my fellow hovercrafters, but, HP is the calculated output based on compression ratio and final combustion pressure at a specific RPM.



BHP Brake Horse Power is measurde on a dyno, (engine test device) this measures what the engine is actually giving at the output shaft. The power is usually absorbed using an alternator or a water brake.



BHP at the wheels is very different and this is measured on a rolling road and takes into account loses, through transmission, clutch etc. Car manufacturers do not normally quote this figure. As a rule you will only get 85 - 90% of the crank power delivered to the wheels.



When a manufacturer claims 50hp, out of a batch of engines he has made, one of them (which they keep as a reference engine) does produce 50hp. The rest of the batch, depending upon which ISO or Din spec is used must produce 85% of the reference engine to be accepted as a good engine.



If you look at the Briggs 20HP, tested against the J823? test, that is without generating coils, not intake filtre and no exhaust. This engine standard only produces 18hp.



There are some good engines and some real ************, just the luck of the draw.

hoverchaps - n/a
29-Jan-08, 09:35 PM
Is the point of 503 to be a standard engine. If by removing the air cooled fan gains hp is this not outside the rules?????

Vortex - n/a
29-Jan-08, 09:41 PM
There by hangs a ........



You can buy free air cooled engines from Rotax, so technically they are standard, however if you use non Rotax pistons, gaskets, plugs, springs etc etc...then in theory.......it is not a 'standard' engine.

hovmart - n/a
29-Jan-08, 10:06 PM
is the class just for rotax 503 or air cooled under 500cc

sixpackpert - n/a
30-Jan-08, 07:36 AM
Formula503 is only 503/447 engines.



F1x is upto 500cc, air cooled 2 stroke and 750cc 4s troke thrust engines. You don't want anything less than a 503 or equivalent in F1x IMHO.



Edited for accuracy, and I'm on Comps!! http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

Iceman - n/a
30-Jan-08, 07:46 AM
You can also use 447's in F503 too!



Originally the formula was open to all air cooled engines upto 500cc, I'm not sure when or why it changed but I would hope that if anyone comes along with a different engine (e.g. a Robin engine) then they would be allowed to use it.

hovmart - n/a
30-Jan-08, 11:20 AM
thats my point, there are over 500cc air cooled engines out there for half the price of Rotax, so its actually Rotax only racing http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

hovmart - n/a
30-Jan-08, 11:27 AM
like this one, its not rotax

sixpackpert - n/a
30-Jan-08, 11:32 AM
Formula 503 was brought about by the shear number of them. Originally you had to race in Formula 2 (500cc 2 stroke rules). Because of the large amount of 503 craft racing it was decided to give it its own formula. Formula503 was brought about because of the numbers of craft and the popularity of that engine in our sport.



Formula503 is also a standard formula. No modifications are allowed. Everyone is running the same engine, same power (roughly). If we introduce all different engines then policing the power outputs becomes a nightmare. We are all up for simple rules and great racing. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif



All the above is relevant to F503. You can use the engine pictured for F1x.

hovmart - n/a
30-Jan-08, 11:41 AM
i allways thought that the free aircooled engines had been modified by the importer and that they started life with the cooling fan on,and then you have single carb, twin carb, single or twin plug, electronic or points, diferent exausts roughly all sort of different power, so what standard on a hovercraft http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

sixpackpert - n/a
30-Jan-08, 11:48 AM
Taken from the Racing Guidelines in the downloads section.



c) F503 specifications are as follows:



(a) Single engine standard Rotax 503/447 engine, single fan (excluding

standard engine manufacturer’s engine cooling fan), single duct

integrated craft.

(b) Single or twin carb round slide type maximum bore of 37mm.

(c) Standard Rotax two into one exhaust system (positional modifications to

allow safe fitting of the exhaust to the hull are permitted, but the exhaust

must remain dimensionally the same).

(d) Engine cylinders to be standard cast liners and pistons to be twin ring

type with both rings fitted.

(e) Must be standard Rotax head, additional cooling fins may be fitted.

(f) As of the 2008 season a minimum weight limit of 130kg is likely to

be applied.





d) Formula 1X will be run as a sub category of F1 for the 2007/2008 season.



(a) Formula 1X specification is as follows:

(b) The craft is to have a minimum of 2 engines, one of which must be

for lift only.

(c) The engine for thrust is to be aircooled, up to and including: 500cc

2-stroke, 750cc 4-stroke.

(d) Total capacity of the 2 engines is to be in accordance with 2.5.A.a

or 2.5.A.b.



Hope this helps http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Iceman - n/a
30-Jan-08, 04:38 PM
The origin of F503 was the air cooled trophy that used to be awarded to the highest scoring air cooled engined craft in F2. It was then introduced as a trial so that those drivers who didn’t want to upgrade to the expensive engine or complex setups needed to win in F2, could still have a competition within the formula. As Jon points out, due to the popularity of that, F503 was born and is doing very well.



Originally the rule covered any air cooled engine. When I was on Comps I tried to make sure the door was left open for any other engines but time has shown that the 503 is the engine that people want to use and therefore I guess the rule has been changed to keep matters simple. It is very hard to write rules to satisfy all requirements and all possibilities.



I would like to think that if anyone knew of an engine that was cheap and powerful and readily available, that they would approach comps and put forward a proposal for a new formula. We have seen lots of trials of new concepts in recent years with various levels of success. The bottom line is people vote with their feet and it soon becomes obvious which ideas are worth developing further.



As for ‘standard’ engines, the rules allow for a free air cooled twin carb 503 which is available off the shelf and is fitted to several microlights as standard so there is no argument that in that format, it is a standard engine. Any variations such as fan cooling or single carb does not enhance power output and therefore cannot be seen as an advantage. As for the different ignition, exhaust, etc, systems, they won’t effect performance noticeably. The basic 503’s are all the same and so its as close to controlled engine formula racing as we can get without going stupid.



The argument about using standard gaskets and spares is over the top as far as I’m concerned. Fortunately we are not in a form of motorsport that is taken so seriously that these factors become an issue. The rules are generally taken in the spirit in which they are intended and I don’t think we have anyone buying several 503’s, putting them on a dyno and picking the best one to use!

Mart366 - n/a
31-Jan-08, 09:03 PM
So if i,ve read that right, 447 engines can enter F503?



from what ive seen of 503's racing, they'd leave my 447 standing http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif



what gains on a standard 447 would be unleashed if it went to a two carb setup?



I guess the downside, would be the loss of F3 and junior use





Mart

jon_curtis - n/a
31-Jan-08, 09:05 PM
a 503, aint just a 447 with twin carbs!



a 503 is about 50hp ish a 447 is about 38 ish i think!

kevinf - n/a
1-Feb-08, 09:45 AM
Jon, I'm pretty sure that Martin appreciates the difference between a 503 and a 447, having been around them at plenty of race meetings.



Martin - it's only 2HP difference (going from 39.6 to 41.6), not really worth the expense unless you have all the parts lying around. As you say, you'd lose the use of the craft in F3 and FJ. The only appreciable benefit is to be able to optimise the jetting for each barrel instead of the single carb compromise. When I raced a free-air cooled 503, I often ran a larger jet in the rear carb - or was it a smaller one in the front carb - depends if you are an optimist or a pessimist I suppose. Interestingly, the single carb 447 has more torque and power up to 5000rpm than the twin carb set-up.



Kevin F

GavinParson - n/a
2-Feb-08, 02:45 AM
I used to pick off a few 503 powered craft with my 447 when I raced but it still couldn't beat the majority. There's little point just being an also ran in racing so effectively the use of a 447 is pointless.

This brings us back to the dads and lads concept for which the 447 was promoted a few years back. And as it was shown, unless the engine is competitive for the formula in which dad uses it then it will have little success.



Now the Briggs and Kohlers are pushing the 40hp boundary then hopefully these or similar engines will replace the outdated, still noisy, unreliable and uneconomical 2 strokes.

The 35 Briggs can give great performance and is far cheaper than a 503 and should be seen as an ideal entry level engine.

Certainly once the industrial four strokes break the 50hp barrier then there should be no excuse with continuing with 503s.



Using these noisy engines is hardly the way forward when Keith is doing so much work to make craft quieter and make the sport more environmentally acceptable.

hovmart - n/a
2-Feb-08, 09:44 AM
Kohler are now doing 40 HP so more power than the 447 rotax

Iceman - n/a
2-Feb-08, 10:51 AM
I'm sure everyone fully supports the idea of cheaper, quieter, more economical racing and I would imagine sales of a 50hp 4 stroke that could compete with the 503, (especially on cost) would be high. However, like most things, people vote with their feet and it takes time for 'changes' to happen. Its very obvious that the success of F503 is far greater than F25/F35, which in my opinion proves that performance is of more importance than cost/economy/reliability/etc.



I was one of the comps members who pushed for 447's to be introduced as an F3/FJ engine and like you say, this was to re-introduce a 'lads and dads' type craft (and mum's and gal's of course). But it was not really intended to be a competitive class, more of an easy entry into the sport. Personally I did want to see it developed into a seperate category but at the time it was not seen to be feasible/desirable.



As regards 2 strokes being noisy and unreliable, no-one will deny that compared to 4-strokes, they do have short comings. However, taking 503's as an example, those engines are fitted to aeroplanes and complete many hundreds of hours without so much of a missed beat. However, put the same engine in a hovercraft in a dirty and wet environment and make it work hard without alot of maintenance and obviously the reliability level will drop. I suspect that the same issues will occur with 4 stroke engines and as can be seen on another thread, they are not bullet proof and can blow up.



Noise is obviously our weak point and the work Keith is doing to help us understand it and tackle the issue is obviously a good thing. However, we are a motorsport and noise is part of that and whilst we don't want to alienate ourselves from any circuits, there is nothing like the roar of 25 hovercraft revving up at the green light (or as the red lights go off as it is now!)!



We all have our own opinion when it comes to 2/4 stroke, for the time being I will be sticking with the 2 stroke but I won't be knocking the 4 stroke users or criticising their shortcomings.



At the end of the day, people will vote with their feet so time will tell where we are headed........

hovmart - n/a
2-Feb-08, 01:59 PM
you are right in what you say David and i guess thats why Rotax are stopping making the 503 and 447 and devloping 4 stroke smowmobiles to come in line with all those green rules

tonybroad - n/a
2-Feb-08, 03:30 PM
i still think there's room for both



i'm pushing a new 2 stroke setup which should be significantly quiter than past craft with an affordable and sustainable engine



similarly the arrival of a 35kg 550cc V twin 70hp Aprilia engine at work (not for the hovercraft) has caught my attention as it's sister 450cc V twin is reported to knock out 60+ - easily a competitive 4 stroke F3 engine of the future



ultimatley i think the 2/4 stroke debate may well be skewed by environmental pressures in the future



Tony

GavinParson - n/a
2-Feb-08, 03:32 PM
taking 503's as an example, those engines are fitted to aeroplanes and complete many hundreds of hours without so much of a missed beat. However, put the same engine in a hovercraft in a dirty and wet environment and make it work hard without alot of maintenance and obviously the reliability level will drop. I suspect that the same issues will occur with 4 stroke engines and as can be seen on another thread, they are not bullet proof and can blow up.




The key to keeping a 503 or even a 447 running in an aeroplane as you well know David is letting the engine warm up properly, limiting full throttle to only take off and then backing off to cruising speed, maintaining everything for reliability and have frequent service intervals. In a racing craft most of these factors are thrown away and the engine is pushed to the limit race after race.

Compare that to a standard industrial engine which is so undertuned and is designed to run flat out all day long without breaking a sweat let alone a piston.

Don't confuse that with the industrial engines that have been tuned. Yes we know of a few cases of failure, but I for one do not know of the failure of industrial engines in recent years. (I had various coil and exhaust failures on my CH25, but that was 10 years ago)



Martin, yes Kohler do now produce a "40" engine but the specification list only states 38hp plus the little disclaimer at the bottom which says "actual horsepower is lower".

Obviously they have a blueprinted engine back in Wisconsin so they can claim that a "40" engine can produce 38-40hp.

We know of old that Kohler overstate their figures and we used to see 22hp Briggs performing as well as 25hp Kohlers.



As it stands now, a new 447 is 1,703 and a 35 Briggs is about 1,200 so cost should not be an issue in selecting a four stroke. But the club still can't separate hp from cc so will F25 which was raised to F35 ever become F40 or F50 allowing for maybe a 40hp thrust with 10hp lift?

I still maintain that the sports holy grail is a light, compact reliable 50hp four stroke that everyone would want to use.



The main driving force when choosing engines is price (unless you're at the top of F2 or F1). The secondhand Rotax market used to be full of 447s from microlighters wanting to upgrade to 503 or better and plenty of 600ish 503s. Hovercraft racers wanting a cheap engine choose these. The market is not buoyant with used V-twin four strokes beacuse they <u>are</u> reliable and they usually are part of a log chipper or something.

Probably F35 still suffers from the legacy of the perceived "slug racing" of F25 but it could be something altogether better if pushed past 40hp

hovmart - n/a
2-Feb-08, 03:57 PM
it will not be long before the Rotax Type 1304 102hp and the 810 67 hp v twin fourstroke engines become available from snow mobile salvage and they wiil bring hovercraft forward from the very old 503 and 447

RHudson - n/a
2-Feb-08, 07:01 PM
There seems to be a very strong feeling for both 2 stroke V's 4 stroke engines about to develop, however (and this is my own personal feelings) 'racers' will go with what works - which is currently the 503 (in this case) which is light - compared to the 35hp Briggs, its very light, and the only people that win with heavy engines are formula one (although not very often) and Tony G at the moment (and fair play to him, but God knows to make it competative took time and a number of engines, correct me if I'm wrong Tony (please)). Agreeably the same could be said for a 503 but comparativly they are a) easier to maintain in a field and b) an awful lot eaisier to work on. We are after all talking about RACING (not just going out to make the numbers up - because I'll bet that most people who race are actually dreaming of winning and not just making the numbers up, or why bother going racing!!!), thus to be competative means to keep developing to stay ahead which ultimately will result in engine enhancements/reduced engine reliability.

Yes Fuel consumption is higher when coupled with oil costs and noise may be higher - but I'l bet that the comparisons between a reasonably silenced 503 RACER and a 4 stroke cruiser (read in, shut back the revs to 3000rpm - I know cos I've got one)at full chat i.e. 3600-4000rpm, ! aren't massive.

Once again my opinions but those of us that race (and quietly cruise) seem to get slated for not using a nice quiet cosy fuel efficient 4 stroke when nobody gets on Valentino Rossi's back for racing an unsileced 4 stroke under the premace of development. 'Nuff' said......

sixpackpert - n/a
2-Feb-08, 08:26 PM
There seems to be a very strong feeling for both 2 stroke V's 4 stroke engines about to develop, however (and this is my own personal feelings) 'racers' will go with what works - which is currently the 503 (in this case) which is light - compared to the 35hp Briggs, its very light, and the only people that win with heavy engines are formula one (although not very often) and Tony G at the moment (and fair play to him, but God knows to make it competative took time and a number of engines, correct me if I'm wrong Tony (please)). Agreeably the same could be said for a 503 but comparativly they are a) easier to maintain in a field and b) an awful lot eaisier to work on. We are after all talking about RACING (not just going out to make the numbers up - because I'll bet that most people who race are actually dreaming of winning and not just making the numbers up, or why bother going racing!!!), thus to be competative means to keep developing to stay ahead which ultimately will result in engine enhancements/reduced engine reliability.

Yes Fuel consumption is higher when coupled with oil costs and noise may be higher - but I'l bet that the comparisons between a reasonably silenced 503 RACER and a 4 stroke cruiser (read in, shut back the revs to 3000rpm - I know cos I've got one)at full chat i.e. 3600-4000rpm, ! aren't massive.

Once again my opinions but those of us that race (and quietly cruise) seem to get slated for not using a nice quiet cosy fuel efficient 4 stroke when nobody gets on Valentino Rossi's back for racing an unsileced 4 stroke under the premace of development. 'Nuff' said......






Sat here for ages thinking of a reply but you just managed to sum up what I wanted to say, Cheers Russ! http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif



Quick idea for the mods, can we have a '2-stroke v 4-stroke' forum as most of the threads seem to end up talking about it. Maybe it's time to put up another forum to discuss exactly this matter as it will have a big bearing on the future of racing for the club.



Just a thought, no flamings please. http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

GavinParson - n/a
2-Feb-08, 09:16 PM
At the end of the day this is about the "one engine" formula which is currently Rotax 503. Any talk of improvement or modification is disallowed and can only be implemented on the hull and fan setup. What I'm talking about is what may happen in the future and it needs to be another readily available engine which may not include two strokes for a variety of reasons. And that may include legislation or the loss of more venues due to noise.

Iceman - n/a
2-Feb-08, 09:37 PM
There are two "one engine" formulae, F503 and F25/35. The latter does allow more than one manufacturer but is essentially about keeping a level playing field by engine 'control'.



There is no reason why a proposal for a new formula cannot be made. If someone finds a suitable engine (such as the little Rotax 125 that Tony is using) and can propose some basic rules then I'm sure comp's would consider giving it a trial within a current formula (as it did with F25 and F503). Then its a case of seeing how it goes!



As regards losing venues because of noise, I think the real issue is that there are too many people in this country who whinge and moan about other people having fun. We should be campaigning to make the rules regarding noise complaints to take into consideration the 'density' of complaints from a given area! One or two complaints that represents a tiny fraction of a percent of the locals should not be sufficient to influence an event happening.



(I think Jon is right, this thread has kinda wandered off from the 447/503 stud pattern question!!)

Jamie Lewendon - n/a
3-Feb-08, 11:01 AM
Comps are quite happy to trial new formulae, we tried F503, that worked so was adopted, we tried FS, that didn't work, so was shelved, and now we are trialling F1X, to try and encourage people to "move on" from F503. It could be the F1X rules need tweaking to allow some more options, however we cant generate the rules on the back of information we don't have. Anyone accusing us of sitting on our backsides not trying anything new, obviously hasn't been to a race meeting for 5 years http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif



A big problem with generating rules, is they must be enforcable in a field. HP restricted engines are impossible to enforce in a field, cc limits are measurable with basic tools. Kart racing have similar issues, they solved them by having "sealed" engines, however this makes a cheap engine more expensive, and means the driver cannot make any repairs whilst at a meeting. This means the average driver needs 2 engines, not 1.



Jamie

bryan - n/a
3-Feb-08, 11:15 AM
Well maybe this is the time to push for a General Purpose craft.

There a few hulls about which can be converted.For example my craft has been designed for just this.Its engines are a 14.5 hp

briggs for lift and a bmw k100 for thrust both engines for a grand.I have raced F1 with the craft although its not an 809 powered machine it keeps up with the F1x craft.Kieth has done a noise test and at full power it didn,t exceed 90 dba. After putting the craft through 150 hrs + of racing and cruising are these type of craft the way forward.Craft comes as a kit for less than 6000+vat.Bargin!

Iceman - n/a
3-Feb-08, 04:06 PM
<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Quote:</td></tr><tr><td class="quote">
are these type of craft the way forward
</td></tr></table>



It depends! Is your craft as much fun to drive as an 80hp/125kg Primo? I doubt it in my opinion and therefore won't appeal to me. But everyone is different so its a case of trial and error.



I think FS failed because it was put in the wrong place. I think there would be a high demand for a formula that was basically F503 but with a higher power availability. The simplicity of F503 is very appealing to me but I would like to play with more than 50hp. My 493 single fan craft probably wouldn't win any F2 races but I would love to race against similar type craft. Put FS in with F1 (as the number of craft there is low at the moment) and maybe it will have more takers. I know if I could race mine within F1 then I would!

hoverchaps - n/a
3-Feb-08, 04:51 PM
I did suggest to allow 600cc 4 stroke in f3 but comps did not go for it, so it has been suggested. but comps decided to recycle the 503 again.



any other ideas

bryan - n/a
3-Feb-08, 04:51 PM
I always love the racing and found my last F2 craft a blast.But for a 10 grand craft for 7 meetings a year i found i never got my blow for my buck.So i traded up for a craft that cost less and can be used every weekend. To travel on open water at speeds upto 60mph thats enough buzz for any racer or cruiser!!I can also count the number of new racing craft this coming year on one hand.On a positive note this craft was designed to bridge the gap between racer and cruiser.F25 ,F35 have done well but for the quicker racers these low powered craft just don,t offer the same performance. This craft has been built to be fitted with

3 different motor types.F35 cruising,BMW K75 Cruising and F1x,or BMW K100 cruising and F1.When did the last racing craft complete 150hrs in a year!!!. This is not a craft to replace the 503 or 503 in F1x but just another alternative.

Jamie Lewendon - n/a
3-Feb-08, 05:10 PM
I did suggest to allow 600cc 4 stroke in f3 but comps did not go for it, so it has been suggested. but comps decided to recycle the 503 again.



any other ideas






Duncs,



I fail to see how refusing to allow more 100hp engines in F3 is "recycling the 503 again".

Your argument was that there were plenty of cheap 600cc 4 strokes available. If this was the case why are they not in F2 with all the 100HP thrust engines.



100HP is too much for F3, if you wanna use a 100HP thrust engine, put it in F2 and race against other craft with the same power.

Iceman - n/a
3-Feb-08, 05:18 PM
I think your craft sounds perfect for that role and it does sound like a superb way to spend 150 hours! The problem is, how many people want to race AND cruise? With the success of the Severn cruise and other events, it appears the numbers of 'dual hoverers'are increasing! So we may see in the next couple of years a move towards craft like this, OR, even better, an influx of new members who are attractd by the dual purpose craft.



My philosphy has always been about 'opening doors', trying to allow as many people into the sport by making it as flexible as possible to accomodate the widely varying requirements and ambitions that our members have. Its not about choosing one idea over another or who's opinion of what we should do is right. If we all go out and promote our ideas and concepts then hopefully we can all help to increase the popularity of the sport!

sixpackpert - n/a
3-Feb-08, 05:22 PM
<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">hoverchaps wrote on Sun, 03 February 2008 17&#58;51</td></tr><tr><td class="quote">
I did suggest to allow 600cc 4 stroke in f3 but comps did not go for it, so it has been suggested. but comps decided to recycle the 503 again.



any other ideas








100HP is too much for F3, if you wanna use a 100HP thrust engine, put it in F2 and race against other craft with the same power.
</td></tr></table>



The Dutch do just that with a good success rate, Frank was rattling along at a good rate at Whittlesey, until it died. Pulling that out was a fun experience!

bryan - n/a
3-Feb-08, 05:32 PM
Cracking answer David I support your thoughts what more can i add.

Iceman - n/a
3-Feb-08, 05:35 PM
You could mention my good looks........http://hovercraft.org.uk/images/icons/smiley_icons/icon_wink.gif

GavinParson - n/a
3-Feb-08, 06:57 PM
how many people want to race AND cruise? With the success of the Severn cruise and other events, it appears the numbers of 'dual hoverers'are increasing! So we may see in the next couple of years a move towards craft like this, OR, even better, an influx of new members who are attractd by the dual purpose craft.






http://hovercraft.org.uk/images/icons/smiley_icons/icon_uhoh.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_uhoh.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_uhoh.gif



For Gods sake, isn't that what we tried to achieve with coastal racing but no b**g*r could be bothered to support it.



Surely racing and cruising with the same craft IS a good thing!

Iceman - n/a
3-Feb-08, 07:19 PM
Margaret Thatcher was born in Grantham, a town not far from where I live. Many years ago, someone came up with the idea of a Thatcher tour to show visitors where she was born, grew up, etc etc. However, despite lots of publicity (including TV), the tour failed to attract one single customer!



People will vote with their feet. If an idea doesn't take off then I'm afraid it either isn't attractive enough to the majority, it clashes with exsisting activities or it wasn't promoted/organised/presented in the right way.



I have no idea why the coastal championship didn't take off, I only heard good comments about it, but for whatever reason, it didn't. Thats not to say there was anything wrong with the idea or that it won't take off in the future but it doesn't matter how passionate a small number of people are about something, that alone will not attract others.

Richard Wiles - n/a
10-Feb-08, 10:01 PM
I agree with David,



Fs is a great formula for us.



WHY



1ST Its simple to build and maintain.One engine,One fan.What a great beginner formula.



2nd No Restrictions.Use what engine you want from any background

and what you can afford.



3rd Its a formula which will need no rule changes every two years,And no policing regards to engine mods,over boring,and weight limits.



We need a class which will allow you to use the craft you've got.If its got an engine and a fan you can bring it along and enjoy it.Yes i know you will say you can use it in other current formulas.But why would you put a vangaurd powered craft in F1,It not all about CC.



Lets face it FS was never going to survive in the opens,If the time table was running late you didnt get an open race.



FS was the most fun i've had in racing,Its a World/ European formula why not support it



Richard Wiles

Mart366 - n/a
11-Feb-08, 07:21 PM
With out wishing to divert off topic, i recall certain aspects of the coastal racing scenario , caused some heated discussions regarding types of craft suitable to race, let alone angines.



Mart