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peterburley - n/a
4-Jan-08, 04:13 PM
Hi,



I have a plywood hovercraft, possibly an old Eagle, but it doesn't have an engine.



I'd prefer a small 4-stroke and I've been offered a Honda 250cc Super Dream.



It's a twin, electonic ignition, probably electric start too, but I can get the whole bike and use whatever I need.



Is it possible to use this engine or will it cause major problems?



I'm not sure but I belive the Honda is a 'wet' primary chain, ie, the chain runs in oil from the sump (I need to confirm this before I buy the bike).



Regards

Peter

hoverchaps - n/a
4-Jan-08, 04:45 PM
Toooooo heavy try to get a cb500 been used and ok

Richard Wiles - n/a
4-Jan-08, 06:33 PM
Hi Peter,



I have a CB500 With its running gear (5000 miles - 1998)

I used one of these in an intergrated hull and found it reliable and very cheap to run.I made a couple of mods to mine which i found to be well worth the effort.

I am looking for 250 for it

If you are interested.



Richard



pythonmotorcycles@btinternet.com

jon_curtis - n/a
4-Jan-08, 07:00 PM
the honda engine is wet, and very heavy for the power output! i wouldnt bother with it. if memory serves they are less than 40hp?

Ian Brooks - n/a
4-Jan-08, 07:48 PM
Much less than 40hp... maybe 25 Japanese horses, and to get those you had to wring its neck without mercy!

Ian

peterburley - n/a
5-Jan-08, 04:44 PM
Hi,



thanks for the advice.



the previous owner said it originally had a 2-stroke engine that had 'blown' so he removed it but didn't get around to replacing it with another.



I understand that it was a 250cc of some kind, with a power output of 18 BHP or something close.



As I understand it, a 500cc engine with 40 BHP would be a waste of power unless I changed the duct and fan to use that extra power. Is that correct?



Someone local suggested the Kawasaki 500 engine but it develops 50 BHP and is a beast of a machine. Far too heavy for the hull that I have.



If I'm going down that route then I'd prefer to start a completely new craft.



There are lots of cheap 250cc 2-stroke bikes available, maybe that'll be my best option to get some use out of this one?



I'd really like to build a two engine 3 - 4 seat cruiser but that's a long-term goal. If I can I'd like to get this one running this Spring.



Regards

Peter

jon_curtis - n/a
5-Jan-08, 09:48 PM
whats the diameter of your duct?

peterburley - n/a
6-Jan-08, 04:22 PM
Hi,



I've not measured it but I would guess around a couple of feet, 60cm.



When I asked what sort of speed it could do I was told around 20mph...it's not a 'racer' http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif



Regards

Peter

Paul Fitz - n/a
8-Jan-08, 10:55 PM
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As I understand it, a 500cc engine with 40 BHP would be a waste of power unless I changed the duct and fan to use that extra power. Is that correct?
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No. If the craft has a 700 or 750 duct with a 6 blade fan, both are capable of absorbing about 47Hp at 45deg and 37deg pitch respectively, when spinning at 3300rpm. So 40 HP should not be a problem. You will probably have to change the gearing. If the blades are other than PAG (White/Natural) change them.



If the duct is smaller than 700mm then even with this power, the performance will be marginal due to the low air volume from the fan even at higher speeds.



The biggest problem is likely to be the weight. The 500cc engine is probably much heavier than the original and will need to be placed further forward in the hull. Weight and balance of the hull will be the first thing to sort but it is achievable.

peterburley - n/a
10-Jan-08, 06:49 AM
Hi,



thanks for this.



I need to check the size and type of fan but it's dark when I get home and everything's sheeted down so it'll be the weekend before I get to do it.



Assuming I'm right and I have a 600mm duct, from your message you seem to be saying that adding a 40+ HP engine wouldn't give me much more output than a smaller, say, 20HP engine but with much more weight?



So I really need a smaller engine, 250 - 350cc?



It's looking more and more like a 2-stroke (and I hate those!)...



the fan has, AIR, ten blades, five white full length and five black 3/4 length. I think it's a Hascon but it definately does have fixed blades, ie, I can't change the pitch.



Regards

Peter

hovmart - n/a
10-Jan-08, 07:44 AM
what you need is a bigger duct and bigger fan

jon_curtis - n/a
10-Jan-08, 07:48 PM
hi



what do you mean when you say some blades are full lenght others are shorter?



combination of different colour blades also sounds ominous!



it might be a good idea for you to post a photo of what you have got! sounds like the fan may need to be updated!

peterd51 - n/a
15-Jan-08, 07:22 AM
Hi,



isn't the size of duct irrelevant?



Yes, a bigger duct and fan would allow a bigger, heavier engine to be used, but if it's been working with that duct and fan then it'll work again once an engine is installed.



When I first arrived here everyone complained about my old wreck as it had a 2-stroke engine. Fair enough, they can be loud, they can be unreliable...



but reading further over several months it appears that a lot of people who seem to have been here for a long time and are accepted into the 'clique' use 2-strokes and it's OK for them.



So why isn't it OK for everyone else?



There are very expensive Rotax engines that everyone seems to think are wonderfull, but aren't these 2-stroke?



So, can't this guy just fit a small 2-stroke like a 350cc Yamaha (I recall that these were used years ago)?



Regards

Peter

sixpackpert - n/a
15-Jan-08, 07:58 AM
but reading further over several months it appears that a lot of people who seem to have been here for a long time and are accepted into the 'clique' use 2-strokes and it's OK for them.



So why isn't it OK for everyone else?



There are very expensive Rotax engines that everyone seems to think are wonderfull, but aren't these 2-stroke?



So, can't this guy just fit a small 2-stroke like a 350cc Yamaha (I recall that these were used years ago)?



Regards

Peter






Many of us use 2-strokes in the racing side of the club because they offer good power for little weight.



Many use 4-stroke for cruising because they are quieter and more fuel efficient.



Both engine types have their benefits and their drawbacks. Unfortunately when the argument ignites over which engine type is best it can often lead to a 'heated' exchange. http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif



If you read the posts and try to ignore the childish comments made by some (who probably aren't members of the HCGB and never been to a race meeting/cruise event) you will find some useful insights. You will also spot the posters who have genuine knowledge and are happy to help.



With regard to the OP, if he just wants to buzz around a field then stick a 2-stroke in and away you go!







When I first arrived here everyone complained about my old wreck as it had a 2-stroke engine. Fair enough, they can be loud, they can be unreliable...






Slight exaggeration looking back on your previous posts. Ewan gave you advice on your Kohler as did dangerman and not many had a go at you. Please, there is no need to stir.

Iceman - n/a
15-Jan-08, 11:11 AM
Hi Peter, whereabouts in the country are you? I think it is worthwhile getting a local club member to come and have a look at what you have.



It sounds like you might have a Simple Cyclone and the original engine would have been a KEC or Robin 250cc single cylinder engine. These engines are only about 18 hp and fairly rare so I wouldn't spend too much time trying to find one of those!



From the bits and pieces I have read I think the quickest and easiest way to get your hovercraft working is to find a Rotax 253 which is a 22hp single cylinder engine and although is a Rotax, they are quite cheap. You will need to address the fan as well, depending on your engine choice, pulley ratio and fan hub/blades available you may need to buy new components.



Don't worry if your have old green or black blades, yes they are more brittle tha the newer white blades but they are perfectly serviceable and will get you hovering!



The other critical aspect to ensure your hovercraft works and moves well is to check the skirt. No matter how much power and how efficient your hovercraft is, with a skirt that has seen better days, you will always be dissapointed.



I am sure others will tell you to change this and that but I think its always best to get what you have working with the least amount of effort and expenditure, then you will be hovering sooner and will have a better understanding of it all and will form a better idea of where you want to go with the hobby.

peterd51 - n/a
15-Jan-08, 11:58 AM
Hi Sixpack,



I'm not trying to stir anything up, just pointing out what 'an outsider' sees when he/she first logs in.



Some people will offer help, as you rightly say, but other can't seem to see what's required and basically seem to be saying scrap it and start again.



I came to this thread from the other one about the end of the large model project, where it seems to be moving towards a discussion on what can be done to make this forum more welcoming, so I guess we shouldn't hijack this thread as this debate will probably run in there.



Regards

Peter

sixpackpert - n/a
15-Jan-08, 12:06 PM
Hi Sixpack,



I'm not trying to stir anything up, just pointing out what 'an outsider' sees when he/she first logs in.



Some people will offer help, as you rightly say, but other can't seem to see what's required and basically seem to be saying scrap it and start again.



I came to this thread from the other one about the end of the large model project, where it seems to be moving towards a discussion on what can be done to make this forum more welcoming, so I guess we shouldn't hijack this thread as this debate will probably run in there.



Regards

Peter




Hi Peter,



Completely agree, this BB should be a wealth of knowledge from and for like-minded people, not a primary school playground at lunch time.



How's the craft looking now anyway?

peterd51 - n/a
16-Jan-08, 06:42 AM
Hi,



I had major problems with the Tillotson carb, probably due to its age, so I picked up a new Lambretta carb off ebay, made a manifold and got the engine running.



The engine is back in the hovercraft and I'm waiting for some decent weather, not freezing cold or belting down with rain, to do some basic testing.



I still think this engine's only a short-term solution which is why I was interested in this thread. I'd prefer a 4-stroke but there's not many small ones around. Two local motorbike dealers have both told me that they can get me any number of cheap 2-stroke engines ranging between 250cc and 500cc.



Regards

Peter