Questions for the better informed.

Cox International wrote:Our (and Matt's) KB cranks are identical in dimensions to the Surestart crank and will fit any post 1956 Cox .049 reed valve engine.

However, for reason's unbeknownst, our manufacturer made the actual shaft a tiny bit longer and we now include 2 spacers that buyers can (optionally) use if that bothers them.

Bernie

That's odd do the spacers got before the drive plate?
Live chat?

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

RknRusty wrote:

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

Yes bevause I have a pee wee in need of those their is so much slop in it.

nitroairplane wrote:

RknRusty wrote:

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

Yes bevause I have a pee wee in need of those their is so much slop in it.

Send me a measurement for the Pee Wee and I can see if it is easily sourced.

These Killer Bee spacers fit over the crankshaft between the driveplate and crankcase. You can still use a thrust washer with it. They were a custom project.

Matt

nitroairplane wrote:

RknRusty wrote:

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

Yes bevause I have a pee wee in need of those their is so much slop in it.

That's one thing the PeeWee's never had was a thrust washer and I think they help a motor by not letting aluminum wear and float when flipping them. Theres also the occasional backward start too that can chew on them.

I am aware the aluminum of the case is meant for long wear, but not so sure of the soft driveplate.

Cox International wrote:
However, for reason's unbeknownst, our manufacturer made the actual shaft a tiny bit longer and we now include 2 spacers that buyers can (optionally) use if that bothers them.

Bernie

How much is a tiny bit longer? A couple of thousandths?

EXModelEngines wrote:

nitroairplane wrote:

RknRusty wrote:

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

Yes bevause I have a pee wee in need of those their is so much slop in it.

Send me a measurement for the Pee Wee and I can see if it is easily sourced.

These Killer Bee spacers fit over the crankshaft between the driveplate and crankcase. You can still use a thrust washer with it. They were a custom project.

Matt

Ok then youvmean from the drive plate-the braised when they are furthest apart.

One thing that will absolutely kill top end rpms is a out of balance prop.

I use this little guy from Heads Up RC. I found it more accurate for small props than anything else. One of my ultra secret websites that I don't share that often, lol.
http://www.headsuprc.com/servlet/the-1498/Magnetic-Prop-Balancer/Detail

Bernie,

Is there a recommended procedure for shortening them. I am thinking about just taking it to a sanding disc and going easy and rechecking the lenght often. I will be sure not to over temp it. Am I just being foolish to think I can do it so easily? I have one that I polished and installed in a new crankcase and went through several drive plates until I came across this thread.

Thanks for the help,

Bob

fit90 wrote:
Am I just being foolish to think I can do it so easily? I have one that I polished and installed in a new crankcase and went through several drive plates until I came across this thread.

Bernie may want to jump in and correct me on this one.

The drive plate seats against the shoulder just behind the splines. The problem likely is not the OAL of the crank, but the length of the shaft between the bearing surface on the face of the web and the shoulder. The purpose of the spacer is to fill in the gap between the back of the drive plate and the nose of the case.

I don't think you will be able to easily face off the front of the shoulder without a lathe and some effort since the shaft is hard. You would have better luck counter boring the backside of the thrust plate to allow it to seat further back.

EXModelEngines wrote:

nitroairplane wrote:

RknRusty wrote:

nitroairplane wrote:That's odd do the spacers got before the drive plate?

They go between the drive plate and the crankcase so there's no front to back slop. It'll keep it from galling the reed retainer. Is that what you mean?

Yes bevause I have a pee wee in need of those their is so much slop in it.

Send me a measurement for the Pee Wee and I can see if it is easily sourced.

These Killer Bee spacers fit over the crankshaft between the driveplate and crankcase. You can still use a thrust washer with it. They were a custom project.

Matt

Just checked Matt and the difference at the furthest point is 1.65mm but it is fine as the engine still runs well enough.
But thanks anyway.

Andrew,

Thank you! I never even thought to look at that . I like your idea of counter boring the drive plate. Fast, simple and should be completely effective if done carefully.

Thanks again to all for the education. I obviously haven't finished all my schoolin' yet.

Bob

fit90 wrote: I like your idea of counter boring the drive plate. Fast, simple and should be completely effective if done carefully.

Before I would go to the trouble of counter boring, I would just try it FIRST with the shims that have been posted about.

Just a thought.

PV Pilot wrote:Before I would go to the trouble of counter boring, I would just try it FIRST with the shims that have been posted about.
Just a thought.

That's certainly the quickest, easiest and most practical approach. It would take some care in initial measurament and fairly decent equipment to get the correct counterbore depth -- a little too deep and the crank will bind. OTOH, for some, the enjoyment is in the tinkering.

However, for both approaches, you'll have a limited number of tries to "get it right". The thrust plate is an interference fit on the shaft and I don't know how many remove/reseat cycles it will stand before loosening, so preliminary measurament is imperative.

Probably for almost all flying, shimming is really the way to go. If you're going for "hair on fire" top end, the counterbore may be advantageous. Apparently, the relieved area between the splines and front bearing shoulder is prone to stress fractures. If the nose of the case were faced off slightly and the thrustplate were counterbored to allow an interference fit over the very front of the crank bearing, it might provide enough added support to reduce separation in this area. Gibeault has indicated that a stud is preferable to a prop bolt in alleviating this problem.

andrew

yep, you would have to get it correct on the first or second try, after that I would imagine that tolerances are being lost due to just working the pieces. then start over, ect.

If you go the counter-boring route, it would probably best to use an end mill and make the hole slightly larger than the OD of the crankshaft bearing.

Regards, Matt

I didn't follow completely the debate, but what is the purpose of those two spacers you sell? Are they apparented to thrust washers? And which one would I choose with an hex plate?

Thanks for your help
Manu

Oh, I tough they served as thrust washers... Should have asked it first before making the order... My Venom will be without it then