Cox .049 question
 

Question for you cox .049 guys, i know i can install a TD piston and cylinder on a golden bee.But will it increase the rpms? is there shimming that will have to be done?
Thanks
Jim

Jim,

All Cox .049 engines have the same stroke, so the TD cylinder and piston should not require much in the way of head shims over a stock TD.

Here is a great article by Paul Gibeault that may help you to set up your GB properly. You will probably have to drill out the venturi to get the best performance.

http://coxengines.ca/files/MRP.pdf

Good luck with your hop up!

Bill

Bill thank you for that, that is a very good article, and i will try this information out.
Again thanks and take acre.
Jim

Hi Jim, did you ever ask a grand question. First of all, here are the generalities:

Yes, you can install a TD piston, cylinder and the high compression glowhead.

NO, do not just randomly install any number of head shims. Every High compression head has a squish band;

the distance from the band to the inside head chamber must be measured so that you can add that distance

to the head shims to get a total of .012"-.015" deck clearance. The higher the nitro content of your fuel, the more

deck(head) clearance you need, or you'll blow the element out of those expensive #1702 glowheads.

I used this range in my 1/2A Combat engines and got really good reliability, using 30%-38% nitro fuel.

I also used .012"-.014" head clearance in my class 1 reed valve mouse race engines. I got really good reliability and

fuel range using 30% and 40% nitro fuel.

Okay, you're not done; all Cox engines usually need to have the cylinder shimmed to raise the cylinder shelf

that's the thing the glow head with head shims rests against. The piston at top dead center MUST be even

with that cylinder shelf. Later I'll edit in where you can get those brass cylinder shims from. They come in a set

that usually has a .001", .002" and maybe a .003" size shim.

My best reed valve mouse engine would turn 22,500 rpm without breaking, using a breakin test prop.


One last thing, for Reed Valve Mouse racing, DO NOT Drill out the venturi. The more you open it up,

the worse your fuel consumption becomes. I apprenticed Class 1 with Joe Klause and John McCollum that at

the time were one of the top Mouse cl-1 racing teams in the country. They used the small .062" venturi

and added nitro into their fuel, until they got the best acceptable fuel range and speed in their models.


Of course, if you just want to sport fly with your Golden Bee, then you can ignore everything I've suggested.

But please do be mindful of the glow head squish band measurement. That's something everyone with TD

engine setups should be mindful of. Best of luck to you:D

Tony

Hi Again, The guy you can get TD cylinder shims from sells on ebay. His ebay name is Combatalbert.

Here's a contact link, so that you may ask him about the shim availability.:



http://contact.ebay.com/ws/eBayISAPI...d=371124032089

Best regards....

Hi again Jim, I thought I'd best clarify and validate my comment about the squish

band dimension. Dale Kirn along with several 1/2A speed flyers did the leg work.

Dale found that the squish band ledge varied drastically for Cox #1702 glowheads

produced after the middle 1970's. The squish band ledges measured from .002"s

all the way to a .023" extreme. Like I said earlier; you should measure this space

to know how many .005" copper head shims to use for your desired head clearance.

If you don't know who Dale Kirn was, You'll find what you want via google.

Tony