qazimoto

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Ok this is quite easy to do actually. Often .21 sized Buggy and .12 sized car engines are converted to Control line speed engines.

The first pic below shows a Nova Rossi Buggy motor that I've converted. The technique can also be applied to the smaller .12 sized motors as well. The major mods are obvious. The head fins has been shaved off and lots of metal has been removed from the crankcase. What's relevant here is that the small protrusion (for the clutch assembly?) on the crankshaft front has been dremeled off.

The pics tell the story:


A sleeve nut threaded M6 x 1.0 has been made. This is all you really need besides the prop driver. I made mine out of 1/2 AF Aluminium hex bar.

A short M6 x 1.0 stud (off a bolt) screws into the other side of the sleeve nut for the spinner point to screw into. You don't need this so the bit on the shaft can be left there.

Notice that the whole spinner assembly (off an OPS .29) fits on the shaft via a standard tapered collett. Any suitable propdriver of the right size will do.

The prop for the .21 is a 6.5" x 6.5" Carbon Fibre, it and the single bladers below are obtainable in the US off c/l speed suppliers. I can give you the contact.

I'm guessing that your engine is a .12 so a two bladed prop will be too much of a load.

You need a single blade CF prop. Notice the brass counterweight. The assembled prop balances perfectly on a model aircraft standard prop balancer. You can see how the blade is trimmed and then the brass counterweight is shaped till the whole thing balances.

These props are made for .15 sized c/l F2A speed engines which rev into the 40K range. You can see these in operation on youtube.

With such a prop the .12 car engine can easily rev into the high 30K or low 40K with safety. CF props are very rigid and incredibly strong.

The nice thing is that the problem with your tach just goes away with a single bladed prop. The tach will read half RPM so you just double your readings.

apparent 20K = real 40K.

For starting I'd suggest a simple sleeve nut with a hole for the protruding part of the CS in the front but shaped so you can use an aircraft starter.

I'd leave the r/c throttle and the head fins on!

Hope this helps.

Ray

asmund

That is great information right there[sm=thumbup.gif] This must be how to do it for someone who like to tinker themselves, be sure to get those special props, do not miss the importance of that, or bad things WILL happen[X(]

qazimoto

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A source of good quality Carbon Fibre props in the US is Eliminator Props. Their catalog is attached below.

The link directly below is where I get my stuff from in Australia. This bloke is extremely busy because it's a FAI C/L World Championship year and this is where the fast guys get their props.

Check out the technical articles.

http://www.supercoolprops.com/

This one sort of explains some of the issues relating to single bladed props.

http://www.supercoolprops.com/articles/propdocf2a.php

regards Ray

gkamysz

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Testing a car engine for performance should be done on an inertia dyno. It's the quickest way to get a curve through the entire RPM range. A prop will only give data for one speed. Do the math and make sure your flywheel is safe at the speed you want to run it. The clutch will not disengage until RPM drops below engagement speed. This is a simple fact of life with a centrifugal clutch. You can use a one way bearing to allow the flywheel to overrun, or put a brake on the flywheel and use it, to prevent the engine from being run so fast with the throttle closed(read no oil flow). Props can be used, but then you're talking many test runs to generate a curve. Who uses a dyno? Mostly the engine tuners. Google and youtube turn up plenty of information about inertia dynos. An inertia dyno needs some electronics to get the data. At the bare minimum a rev counter with a timer, the rest can be done by hand.

Frank Ts Stuff

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IT is an AWESOME Tach designed and built by a dear friend of mine who we sadly lost a few years ago, Tony Neapolitan Criscimagna (T.N.C.). an amazing inventor who can lay claim to inventing among other thing the plasma screen!!!

http://www.google.com/patents/US4611203