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keitht
16-Sep-10, 07:54 AM
I have just built an eagle 1 with a 600cc 4 cylinder bike engine , it has a 900mm 9 blade fan with a 45 decree pitch. Had a test run last night , front end lifted at about 8500RPM (engine ) but back end lift and thrust at about 10500 (engine screaming) if I increase the pitch would it give more lift and less revs, Can anyone help.

atters
16-Sep-10, 08:28 AM
Sounds to me that you go a ratio problem, with that amount of pitch on the blades, the engine should not be able to rev that high. Any pictures available?

keitht
16-Sep-10, 09:16 AM
Sounds to me that you go a ratio problem, with that amount of pitch on the blades, the engine should not be able to rev that high. Any pictures available?

I have attached two pictures, I sent all the info for the gearing of my engine to Ken at K&M Products and he sent me all the parts required and told me to run it in third gear, I tried 4th 5th & 6th gear but not much better.

Al
16-Sep-10, 10:02 AM
If your splitter plate is correct and you bulit the hover to the plans, then I agree with Atters, it must be a gearing problem. How many teeth does your belt pulleys have on them (drive & driven)?

idefix
16-Sep-10, 10:10 AM
Hi,
You have to consider that the weight is your enemy.
What is the weight of your engine?
Which is its power curve and to which rotation speed?
On photos it seems that you use a multiwing 5Z blades.
For me the optimal rotation speed of your fan is 2000 rpm
It is possible that your ratio is not correct.

regards

idefix

keitht
16-Sep-10, 10:12 AM
Thanks guys, I have just spoke to Ken and it looks like I've set the pitch all wrong, I will try it tonight and let you know how I get on, sorry for wasting your time, "novices" who needs them ?

lyne0990
16-Sep-10, 10:43 AM
Novices! The Club needs them. Never be afraid to ask.

Jim

atters
16-Sep-10, 10:59 AM
No worries mate, I had the same trouble with a 400cc honda engine I had, Found that it needed to be in the highest gear there was, either 4 5 or 6, I eventually dumped the bike engine for a Rotax 503.

Hang in there, I think the 600cc you have could work well and looking at the pics you have done a great job so far.

gaz
16-Sep-10, 04:25 PM
Someone in the club once told me it is rare to get a hovercraft to work "out of the box" hang in there and ask those questions. Most people on here have been through what you are experiencing. Once your teething problems are ironed out you will soon forget there were ever any!

Al
16-Sep-10, 08:54 PM
Someone in the club once told me it is rare to get a hovercraft to work "out of the box" hang in there and ask those questions. Most people on here have been through what you are experiencing. Once your teething problems are ironed out you will soon forget there were ever any!


I had teething problems with my surveyor for about a year. It come very close to going on ebay to join all the other hovers on there for sale that have teething problems:D

Seriously as Gaz said keep asking questions as someone in the club will have the answer. Eventually it will all come together & you will wonder why it took so long to iron the little problems.

keitht
17-Sep-10, 12:23 PM
Thanks for all your comments

Had a go last night at re-setting the pitch,(Grinding in hub bearings) not good ! Will replace before next test, When I spoke to Ken he said there are four dots on the root of each blade 10 degrees to 50 degrees, Line the blades to 45 degrees inbetween the 40 & 50 dots with the split in the hub, is the 50 degree dot nearest the leading edge ? I've been looking for a diagram online to see how to set the pitch but can't seem to find one.

gaz
17-Sep-10, 01:18 PM
I think your after this LINK (http://www.google.co.uk/url?sa=t&source=web&cd=1&sqi=2&ved=0CBgQFjAA&url=http%3A%2F%2Fwww.ace-coolers.net%2FManuals%2FCrowleyFanManual.pdf&rct=j&q=multi%20wing%20america%20pitch&ei=4GWTTKygB8LfOJzNmZ8M&usg=AFQjCNGrTVzYk3dpks8HdFjFiVC7_PL3tQ&sig2=EkIP0sKR_JmXJRcbgs0TaQ) for the Multi wing blades pdf, or this LINK (http://www.hascon.it/en-US/WebSite/HasconWing.aspx) for one from Hascon, just download hasconwing2008eng.pdf and you will hopefully have the data you need

Paul Fitz
18-Sep-10, 02:57 PM
....if I increase the pitch would it give more lift and less revs, Can anyone help.

No. You do have a poor ratio. The 900/9-9/5Z will absorb your engine power at approx max engine revs, but at 45 deg. the fan will be developing a large volume of air (good for top speed and into wind performance) but a marginal pressure (probably just sufficient to lift it reliably). ((This is a typical racing type choice.)) at lower revs the pressure will drop to inadequate levels as you have found.

At a lower pitch (eg. 35 deg) for a given speed the fan will provide the similar pressure with lower volume and about 1/2 the power consumption. i.e it will allow the engine to rev further giving "emergency power", but the ratio needs to be changed to obtain this.

idefix
21-Sep-10, 03:37 PM
Hi,
A 900 mm 9/9 at 45 will absorb 51 Kw at 2500 rpm (+/- 70 HP).
If your engine developpe such power, you must use a ration like 3.4 (2500 rpm on fan and 8500 rpm on engine).
Have you try a lower pitch ?

Bryan
21-Sep-10, 07:36 PM
Hi i have used many bike engines in the past. Remember your have 6 gears in the box. Pitch those blades at 50 degrees and put the motor in sixth. Now thats your start point. Try the craft and take note to see if the motor pulls through upto max rpm. If not don,t alter the pitch just knock it down a gear and retry right through the gear range. Take some notes!!. If your engine red lines in 6th gear at full pitch then change your pullies.
That craft of yours will be very rear heavy. This maybe a big part of the problem. But good luck and crack on.

keitht
28-Sep-10, 02:03 PM
Thanks for all your advice, Looks like I gave Ken the wrong info at the start regarding the gear ratio, 2 full turns of the crank ( which is the engine cycle) instead of 1 turn for the gearbox, so I'm out by 2 to 1, have ordered smaller top pulley & belt, fingers crossed.
PS Photo's attached, It's getting there.

keitht
11-Oct-10, 02:15 PM
Fitted new pulley & belt, still seems high revs to get going, tried it in 5th gear with 50 degree pitch , started to lift at about 7000rpm but took up to 10,000 rpm to get moving, once going could ease back to 9000rpm but engine started to overheat, someone mentioned a 35 degree pitch in 6th gear , would reducing the pitch allow the revs to drop ? Also steering seems to be non existent ( or is that normal )

atters
12-Oct-10, 09:07 AM
for a first flight, yes. it is normal to have no control. Take the advice, start at 30 deg in 6th. Always use the highest gear you can, rather have the blade angle less than the gear ration not right, you will not get the most out of the motor if the ratio is wrong.

Chuck it in 6th and then bring the blade angle down a work up slow till you get the revs you want, it should easily rev once the blades are set low, if you rev past what you want, then just change the blade angles a bit and have another go. It will take some time of fiddling but you will get a feeling of how far to move the blades as you go.

keitht
12-Oct-10, 06:35 PM
Thank's very much I'll give it a try (fingers crossed )