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normlee

Well-Known Member
Joined
Feb 13, 2015
Messages
579
As I have no time to run in engines at the pond I'm going to build an aero prop setup with a full shroud and flex cable linkage. Looking for suggestions to prop sizes for 21 45 and 90 engines please. Hoping I can cut down larger props for strength @ higher rpm.
 
I wish, easy to run an engine on a sunday arvo at home rather than drive an hour to the club once a fortnight. I get days off during the week, makes sense to me, maybe not everyone.
 
Was thinking of this myself, simple flex cable and pillow block with bearings at the stub shaft. Some sort of flange threaded on to hold the prop.

A pusher prop would keep the exhaust from blowing back at you.

I know from experience years ago to get the biggest prop you can and cut the blades down to get the rpm you're after.
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Pm Jim Allen. His setup.
Ray,the problem with Jim's set up is it would costs LOTS of $$$ and would take 6 months to build!!!
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Norm,go onto Top Flite Propeller website and look up model airplane props and that will give you a starting point,mike.
 
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I have built & I'm using a test stand that uses model airplane propellers. Only carbon fiber propellers are used & they are "CAREFULLY balanced in a magnetic balancer. The test stand is designed to allow the testing of both gas & nitro engines with a simple setup change. The test stand has two custom machined ball & pin universals to make engine to load shaft alignment easy. The propeller shaft (.6250" OD X 17" long) has two preloaded ball bearings at each end. The connecting shaft between the engine used & the propeller shaft is .5000" OD X 10" long. The same universals are used for both engine types, nitro & gas. The test stand uses a Fromeco tach, which is mounted directly behind the propeller. The test stand weighs 30 lbs & is built on a 1.000" thick X 5.000" wide X 36.000" long base. It is secruly fastened to a rigid bench. Carbon fiber propellers can withstand any RPM range possible when using a gas or nitro engine!!

Jim Allen
 
Sorry to take so long to answer Terry, but I had many cylinders to hone & fit this past week. Yesterday we were at the lake testing one of the new pipes on a 35 cc engine. I prefer to use 17" X 6" Falcon brand propellers cut down from 10.5" to 5.5" in 1/2" steps. I open the existing holes in the propellers from .3125" to .3750" to fit tightly on my propeller shaft, which is hardened on the end where the propeller is mounted. After cutting them down they are carefully rebalanced. I also check to see if the propeller sits square to it's propeller driving surface after recutting the existing propeller shaft hole.

Jim Allen
 
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Terry,

There is one thing I failed to fully explain concerning the use of airplane propellers as a loading device. The following information comes from Bolly & was used to prepare the Falcon brand propellers used.

"It is important that propellers be well balanced. The propeller should also sit square to the engine prop driver. Check for an equal height under each tip with the prop sitting on a flat surface.

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Many props (especially moulded nylon types) will have an uneven bottom (and / or top) surface due to uneven material shrinkage. Check this before checking for equal heights below each tip.

It can happen that the shaft hole isn’t square to the rear face of the hub, for this it is a good idea to step or taper ream the prop, leaving only a small amount of the hole at the required diameter."

This is the reason I machined the existing hole in the propeller from .3125" to .3750" while clamping the propeller's rear face to a flat indicated surface. The rear face of the Falcon brand propellers are approximately 1.500" in diameter, therefore there is plenty of area to allow clamping.

JA
 
Terry,

There is one thing I failed to fully explain concerning the use of airplane propellers as a loading device. The following information comes from Bolly & was used to prepare the Falcon brand propellers used.

"It is important that propellers be well balanced. The propeller should also sit square to the engine prop driver. Check for an equal height under each tip with the prop sitting on a flat surface.

Image31.gif


Many props (especially moulded nylon types) will have an uneven bottom (and / or top) surface due to uneven material shrinkage. Check this before checking for equal heights below each tip.

It can happen that the shaft hole isn’t square to the rear face of the hub, for this it is a good idea to step or taper ream the prop, leaving only a small amount of the hole at the required diameter."

This is the reason I machined the existing hole in the propeller from .3125" to .3750" while clamping the propeller's rear face to a flat indicated surface. The rear face of the Falcon brand propellers are approximately 1.500" in diameter, therefore there is plenty of area to allow clamping.

JA

Never heard of that, thanks!
 
Pity Bolly doesn't have anything to do with Bolly anymore!(it's a shame!) Peter Tapp purchased the business and now builds some composite rifle stocks! Not bad for a guy that wouldn't know what end of a gun is dangerous! But that all started whith me stupidly bringing down my Kelbly benchrest stock to show his molding guy! Silly silly me
 
I remember as a young kid ,working in a hardware shop which we was dealing rifles n ammo ,when I saw plastic,/ceramic ruger body,with stainless barrel in the cage ,.223 carbine.

Was good kit.
 
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We called them boat paddle's in Australia i still like the 70s Rugers i own one with the barrel marked with BUILT IN THE 200TH YEAR OF AMERICAN LIBERTY stamped on the barrel! In .220 swift a pesky varmint rifle!! Bolly props (Les Bollenhagen) built some lovely rc plane props in his day! He flew planes with my Dad and grew up next door to a guy called Reg Barrington (a WW2 Lancaster Bomber pilot) that was also a friend of my father! Sorry for thread jacking
 
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