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Old Nov 16, 2012, 03:34 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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Originally Posted by epoxyearl View Post
We've traded the heli drive for a BELT drive. Getting the final drive to turn a prop the "scale" direction was hurtful with the heli parts.

The Engine Masters,whom I hold in high regard,indicated that I had 'way too much power for my requirements.-They said a .46 would turn that gianormous prop at the speeds I require.(32 x 14)...

I think 1500 to 1750 rpms should be fine for 10 lbs of thrust,and 25 mph flight speeds.

So here we are at the beginning-it's like deja-vu all over again! The cooling fan needs some thought,but that's a minor problem.I need to make a set of mounts to locate the out put shaft with the engine,and circumvent the fan. Hoo ruh !
A shortened 3 or 4 blade prop might work for a fan???? Could you use the original fan shroud and fan from your heli set up? You could remove the clutch and bolt on a universal joint..... after a good deal of engineering

Good on ya for the belt drive You will be much happier IMO. Maybe a set of universal joints out of a large boat for the drive shaft??? I personally don't see the need for a center support on the drive shaft. 1500 RPM is pretty slow after all. I can't imagine the shaft whipping at that speed unless it is bent to start with.

The design part can be a challenge sometimes. You are whipping it step by step.

Ken
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Old Nov 16, 2012, 03:56 PM
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United States, MD, Elkton
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WE were able to install the heli fan on the Evolution engine,with room for the belt drive pulley. I may need to trim 1/16" from the face of each blade to get clearance for the belt passing so closely.
I have several junk helis for parts,and I can conjure up a decent ductwork setup.

The 'reverse' engineering is required as I try to make parts serve MY purpose.I have a collection of used parts and engines available,so I'll build it,then do engineering drawings-NOT!

I went to ACE Hardware,looking for some bushings to adapt the shafts to pulleys and found everything I needed.
This is fun ! Thanks guys.
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Old Nov 16, 2012, 06:35 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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Quote:
Originally Posted by epoxyearl View Post

The 'red neck' engineering is required
Fixed it for ya

Ken
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Old Nov 16, 2012, 07:25 PM
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Originally Posted by kenh3497 View Post
Fixed it for ya

Ken
I stand corrected-Whup ! Rotflmao !
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Old Nov 18, 2012, 05:31 PM
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I made an aluminum base plate to mount the engine on...I have some Delrin that I cut for mounting blocks for the beam mounts,to secure the engine and allow minor alignment adjustments.
I'll shim the engine to get proper belt tension..

Why do I need the one way clutch,or do I ? If I lock the driven pulley to the shaft,I can start the engine with prop flips.
At 6-1, I shouldn't have any problem firing it off, and that troublesome boat belt won't be necessary.

The next step is mounting the cooling ducts...I'm encasing the bottom of the plate around the impellor,to seal it,and directing the air past the cylinder.
The plane won't be 'stationary' as a heli is,and I'll also direct cooling air from the prop blast through the fuse in channels.
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Old Nov 18, 2012, 06:03 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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I take it you don't have the fan shroud??? Maybe you do and I missed it. I would save on some of the red neck ingernearing

You might consider a short shaft off the crankshaft to support the drive end of the engine. It would be easy enough to do (easy for me to say) by making a long nut with a stub shaft on the end of it for a bearing. Just make a new nut on the lathe, drill and tap on the lathe for concentrically and then turn a short integrated shaft for a bearing.

Yes no need for the one way bearing on the prop shaft. 6:1 reduction or actually increase might give you a little tougher time starting though. You can always change if you need to.

Looking good so far!!!

Ken
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Old Nov 18, 2012, 06:54 PM
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Lathe? LATHE? All I have is a drill press and a file ! You're getting ahead of me.....there is a set of holes at the point of the crankshaft,where that support bearing will be located. It's in an incorrect position because of the difference in diameter of the drive compenents.
Once I get all the alignments completed,I'll install the front support bearing,as suggested.
If it's necessary to make a drive nut,I'll extend the shaft forward into a bearing.
It's not necessary at this point to do anything other than test run the system and check for 10 lbs. of thrust.
My cordless drill turns the prop at 950 rpms,and there's considerable,but not measurable, thrust..
I DO have several cooling ducts,but the engineers didn't have this contraption in mind,when they designed them.
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Old Nov 18, 2012, 09:39 PM
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The 'Wack, BC, Canada
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Earl, you will most definetly need the shroud to direct the air from the impeller around and thru the fins on the cylinder and over the top of the head. The air coming from the front will simply NOT be enough to keep the engine running cool.

The shroud has to extend back and part way around the fins to duct the air into the gaps and at least partially around the back so the rear isn't sitting in a blob of overheated turbulent air.
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Old Nov 19, 2012, 12:17 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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Quote:
Originally Posted by epoxyearl View Post
Lathe? LATHE? All I have is a drill press and a file !
That will work just fine. It might take you a bit more time is all

I have a small Taig lathe. If you need, let me know and I'll see if I can whip something up for you.

Ken
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Old Nov 19, 2012, 02:22 PM
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WELL !! a couple of test flips showed me that cranking the engine via the 6 to1reduction won't work...When I flip the prop,the belt tends to slip on the smaller pulley,at compression.....If I tighten it tighter than I'm comfortable with,I'm afraid the cords or the teeth may break.,Not to mention bearing loads.
I believe the boat belt starter system may be necessary after all.
I've removed the automatic clutch of necessity,so I can't use the heli starter
shaft as planned.
I'm working on the cooling ducts now while my mind contemplates the starting problem.
A longer shaft would ease several problems in starting,plus give the added benefit of supporting the forward end of the engine..and making alignment more dependable.
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Old Nov 19, 2012, 08:07 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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Don't be afraid to tighten the heck out of those gear belts. You will be hard pressed to break it. I believe Kevlar is a common material used for strength. You are more likely to strip a tooth off the belt if it is too loose rather than too tight.

I was afraid of the gearup causing a starting problem. The support on the crank would allow you a pulley for the belt start......

This is turning into a project! Keep after it and it will give much satisfaction, or, put you in the nut house

Ken
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Old Nov 19, 2012, 08:44 PM
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The Nut House don't scare ME!-I'm actually a recovering psycho !lol
I don't take this stuff all that seriously....I'm having fun,and learning a lot of respect for the guys that think these things up,anyway.
I agree about tightening the belt securely,and with the reduction advantage favoring turning the prop,I'm confident about that being strong enough...
I won't try to start it by 'flipping' the prop though.

Once I get the drive shaft cut to length and the universals installed,most of the set-up will be accomplished.The shaft is a 10 mm OD ,2.5 mm wall thickness hollow shaft,23" long...I'm beginning to think a center bearing will be unnecessary at 2.000 rpms.
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Old Nov 21, 2012, 09:14 AM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
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Originally Posted by epoxyearl View Post
The shaft is a 10 mm OD ,2.5 mm wall thickness hollow shaft,23" long...I'm beginning to think a center bearing will be unnecessary at 2.000 rpms.
My thoughts exactly. 2000 RPM is actually quite slow. Good minds think alike

Ken
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Old Nov 21, 2012, 09:27 AM
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The most direct route.

The Sparky was well recieved at the Old Fart's Breakfast...But there's a sticky wicket,again.
I can fabricate a direct route from the cooling fan to the cylinder by encasing the carb in the cooling airflow duct...-any problem with that ? a mini 'supercharger'?
The air comes from the front of the engine( the impellor is where the prop should be) and the carb will be in the duct.

I can 'dummy' a duct with cardboard , and picturate,if necessary.
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Old Nov 21, 2012, 12:58 PM
B for Bruce
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The 'Wack, BC, Canada
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The airflow in the shroud could affect the carb in any number of ways. It may suck the charge back out or ram it in or possibly have no effect at all. It's a "try it and see" sort of deal. If it doesn't run well then put a hole in the shroud and extend the mouth of the carb out beyond the shroud airflow with a bit of tubing of some sort that pushes on over the mouth of the carb.
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