White backplate size

rodrenz Fri Nov 29, 2013 6:46 am

I have a white u-shape .049 backplate I want to use but the round inside fit is undersize, or loose fitting. It seems to me it should be a tighter fit for better crankcase packing. Any comments ?

Kim Fri Nov 29, 2013 7:24 am

Hi Rodrenz !!! Welcome to the Forum !

Yes, the cylindrical part of the backplate should be a close fit in the engine case...do you know if the backplate is the original that came with the engine ?
There are cast engine cases that have a larger diameter opening for their backplate, and those backplates made for the extruded cases will not fit them.
You can get new backplates from either from Matt at Exmodelengines or Bernie at Cox International Ca.

Welcome again the Forum...It is a Fun Place !

Kim

rodrenz Fri Nov 29, 2013 11:39 am

I compared it to a red product engine backplate and it measured about the same, a hair over 1/2 inch. I also compared it with an aluminum bee tank, the bee tank looks to be 17/32 inch, a better fit.
Rod

Kim Mon Dec 02, 2013 3:00 am

Man, I don't know, unless it's had some trauma or perhaps is a different brand. Could you post a photo of it?

**RknRusty** Mon Dec 02, 2013 2:34 pm

I'm curious about this. Just when I think I'm familiar about the fit and shape of every basic Cox engine part, this pops up. Next time I go out to the shop, I;ll measure and compare. I have a bunch of backplates, brand new and old. I have a postage stamp backplate too, for my speed plane, but it's apparently hiding.

If there is a built-in gap between the reed boss and the crankcase, I wonder if stuffing that area could improve performance. It might draw more fuel on the upstroke, and force it up the bypass ports faster on the downstroke.

Welcome to CEF, Rod.

Rusty Babe Bee .049

rodrenz Thu Dec 05, 2013 9:51 am

The horseshoe backplate round boss is exactly the same diameter as the postage stamp backplate. I guess that answers my question. I just thought it should fit the crankcase better for more efficient packing. Thanks for your replys.
Rod

rodrenz Thu Dec 05, 2013 10:22 am

Picture of backplates

rodrenz Thu Dec 05, 2013 10:28 am

I guess I haven't been able to post pictures yet. I'm still in computer Kindergarden. LOL
Rod

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