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Cox engine spring starter scratch guard.

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Cox engine spring starter scratch guard.

Post  nitroairplane on Tue Jul 17, 2012 4:25 am

Thought today I would share a useful tip for keeping anodised or polished crankcases free from starter spring scratches.
I though of this a couple of months ago but forgot to post it.
You will need some heat shrink tubing and a means of shrinking it.

This is the kind of scratching you will prevent.
Get the shrink tubing just large enough to fit over the drive plate cut it so that there is just a tiny bit still touching the drive plate before you shrink it.

When shrunk it should look like this.

When complete you should still be able to see the black tubing under the spring.


You have now completed your very useful ad extremely simple scratche protector.

Edit:Also works for swan neck cases and Pee wees, for the latter simply select a smaller size shrink tubing.
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Re: Cox engine spring starter scratch guard.

Post  Godsey3.0 on Tue Jul 17, 2012 8:56 am

I always hated scratch marks like that. I actually left the spring off of a couple of my engines to prevent those. That is a nice way to prevent it.

Rolla
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Re: Cox engine spring starter scratch guard.

Post  SuperDave on Tue Jul 17, 2012 9:16 am

Excellent idea!

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Re: Cox engine spring starter scratch guard.

Post  RknRusty on Tue Jul 17, 2012 10:01 am

+1
Great idea. I usually don't care about scuffs and such, just adds character. My engines all have a lot of character. Laughing An RR1 would certainly benefit if you want to put a spring on it. My RR has a standard Bee crankcase, so no big deal.

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Re: Cox engine spring starter scratch guard.

Post  nitroairplane on Tue Jul 17, 2012 2:59 pm

Thanks for the positive responses guys.
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Re: Cox engine spring starter scratch guard.

Post  John Goddard on Tue Jul 17, 2012 3:32 pm

Drat I should've done that on number 18.
Very Happy
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Re: Cox engine spring starter scratch guard.

Post  nitroairplane on Tue Jul 17, 2012 3:37 pm

John Goddard wrote:Drat I should've done that on number 18.
Very Happy
I didn't on 04 but did on 16 Smile
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Re: Cox engine spring starter scratch guard.

Post  John Goddard on Tue Jul 17, 2012 5:09 pm

nitroairplane wrote:
John Goddard wrote:Drat I should've done that on number 18.
Very Happy
I didn't on 04 but did on 16 Smile

Did you run both?
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Re: Cox engine spring starter scratch guard.

Post  nitroairplane on Tue Jul 17, 2012 5:33 pm

John Goddard wrote:
nitroairplane wrote:
John Goddard wrote:Drat I should've done that on number 18.
Very Happy
I didn't on 04 but did on 16 Smile

Did you run both?
Sort of, had trouble with 04 so had to change a few parts before running it but yeah it has run.
16 has been run too, would like to do a Christmas special plane this year and will use one of them.
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Re: Cox engine spring starter scratch guard.

Post  John Goddard on Tue Jul 17, 2012 6:13 pm

We could 04,16,18,19
A Christmas Bee17.......
Very Happy
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Re: Cox engine spring starter scratch guard.

Post  nitroairplane on Tue Jul 17, 2012 6:23 pm

John Goddard wrote:We could 04,16,18,19
A Christmas Bee17.......
Very Happy
That would Bee awesome but it would be putting all put bees in one basket Smile
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Re: Cox engine spring starter scratch guard.

Post  andrew on Tue Jul 17, 2012 6:46 pm

I have not tried it, but there might also be some benefit of adding a piece of small diameter shrink tube to the section of spring that wraps around the cylinder.

Great idea about adding shrink tube to the nose of the case.
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Re: Cox engine spring starter scratch guard.

Post  Mark Boesen on Tue Jul 17, 2012 9:22 pm

hey nitro, thats a pretty good idea!
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Re: Cox engine spring starter scratch guard.

Post  Cribbs74 on Tue Jul 17, 2012 11:10 pm

andrew wrote:I have not tried it, but there might also be some benefit of adding a piece of small diameter shrink tube to the section of spring that wraps around the cylinder.

Great idea about adding shrink tube to the nose of the case.

I wonder if it would cause the engine to retain heat. Good idea Indra!
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Re: Cox engine spring starter scratch guard.

Post  nitroairplane on Wed Jul 18, 2012 5:42 am

andrew wrote:I have not tried it, but there might also be some benefit of adding a piece of small diameter shrink tube to the section of spring that wraps around the cylinder.

Great idea about adding shrink tube to the nose of the case.
Well that sounds like a great idea Andrew next time I'm at maplin I'll pick up one of them variety boxes of shrink tubing because I always seem to scratch the top of crank cases too, I really should just remove the cylinder to put the spring on...
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Re: Cox engine spring starter scratch guard.

Post  roddie on Sat Sep 16, 2017 1:46 pm

Cribbs74 wrote:
andrew wrote:I have not tried it, but there might also be some benefit of adding a piece of small diameter shrink tube to the section of spring that wraps around the cylinder.

Great idea about adding shrink tube to the nose of the case.

I wonder if it would cause the engine to retain heat.  Good idea Indra!

Thread-bump.. I like this idea.. but wonder the same as Ron.. regarding the retention of heat.. Huh... The nose of the case is generally "cooler" and fairly well-lubricated though.

Wondering if maybe "partially" shrinking the sleeve would be better? Shrink it down small enough to where it won't slip-off over the drive-plate. This would allow some space for air.. and also be easier to remove after it gets worn. If shrunk "tight".. the case could be scratched trying to get a blade (#11 for example..) in-between to slice it off.

I got curious.. and found my heat-shrink assortment to do some test-fitting. My smallest size was perfect for the spring-wire. I pushed it on around the loop that fits around the case at the bottom of the engine cylinder.. and a bit into the coiled-section of the starter-spring. Then I applied some heat and shrank-it tight.



My largest diameter of heat-shrink tubing wasn't large enough to fit over a "standard-round" drive-plate.. so I thought; why not slit-it open.. and not shrink it at all.. Paranoid

Most 1/2" nominal heat-shrink tubing won't fit over the standard "round" Bee's drive-plate.. and definitely not over a hex one. I cut the heat-shrink tubing to a length of 1/2" (12.7mm) and slit it open to install it around the nose of the crankcase.




I'm not sure how the slit-sleeve will hold-up.. or stay in place.. but I am sure that it will provide some anti-scratch protection while "in-place".. without impeding the operation of the starter-spring or the engine.
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Re: Cox engine spring starter scratch guard.

Post  pkrankow on Sat Sep 16, 2017 3:41 pm

With some looking heat shrink can be found in clear.
Phil
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Re: Cox engine spring starter scratch guard.

Post  Oldenginerod on Sat Sep 16, 2017 5:51 pm

Roddie. Won't that heat-shrink on the crankcase nose shrink when the engine heats up? I mean, that's what it's supposed to do, right? Since it's now split, there's nothing to restrict it from shrinking as far as it likes. A couple of wraps of insulation tape may be a better option.
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Re: Cox engine spring starter scratch guard.

Post  roddie on Sun Sep 17, 2017 8:41 am

Oldenginerod wrote:Roddie.  Won't that heat-shrink on the crankcase nose shrink when the engine heats up?  I mean, that's what it's supposed to do, right?  Since it's now split, there's nothing to restrict it from shrinking as far as it likes.  A couple of wraps of insulation tape may be a better option.

You know Rod.... Huh... I actually wondered if a non-slit sleeve of it would "self-shrink" with the heat of running the engine.. but I honestly don't think that the front-end of the case gets hot enough.

I have two different types of heat-shrink tubing. The one I used in the photos came from Radio Shack.. and has a more "plastic" (glossy) appearance than other type; which looks more like a rubber (resembles the old neoprene tubing). The latter has a higher shrink-rate and seems to need less heat to activate.

I also tried cutting a 2" long x 1/2" wide strip of thin-clear plastic to coil inside of the starter-spring.. but it could have been cut "shorter".. to maybe 1.25"-1.5" so as not to overlap.




The 1/2" (12.7mm) measurement effectively covers the area of the cases' nose between the drive-plate. If one were reinstalling a crankshaft.. a piece of non-slit heat-shrink tubing of that length could be installed prior to pressing-on the drive-plate. As I mentioned; "my" heat-shrinks' ID was too small to fit over it.

Here's a crazy thought... Shocked How about dipping/swabbing the starter-spring in "liquid-rubber"? Here's a product that I've had in my shop for years.. and it hasn't dried-out. There's a brush in the cap.



Laughing .. do you think it would bind-up the coil? It wouldn't penetrate between the coils.. so they would still move against each-other. The question is; would the liquid-rubber "flex" with the springs' twisting.. or would it "split-out" between coils? Maybe it wouldn't matter.. as long as the rubber stayed adhered? Huh...



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Re: Cox engine spring starter scratch guard.

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