What is the thread of a Cox Tee Dee 020 carb body?

[Cox International]

Does anyone (with absolute certainty) know the thread size of the 020 carb body? We are currently manufacturing an aluminium version.

Unfortunately, TD 020 drawings seem to be the ones we are missing.

We gauged a venturi and bought the tap we believed to be the right one but it is not a fit.

Bernie
www.coxinternational.ca

[Cox International]

... echo....

Tough question, eh?

Bernie
www.coxinternational.ca

[nitroairplane]

... echo....

Tough question, eh?

Bernie
www.coxinternational.ca

Ok i have one i will go and look.......

[Cox International]

I am not sure that looking is going to do much good lol.

We have them here and they gauge out at 8-40 but the 8-40 tap that was purchased does not seem to fit properly. Really weird...

Bernie
www.coxinternational.ca

[nitroairplane]

I am not sure that looking is going to do much good lol.

We have them here and they gauge out at 8-40 but the 8-40 tap that was purchased does not seem to fit properly. Really weird...

Bernie
www.coxinternational.ca

true looking didn't do much good!
Maybe the tap was not correct and your measurement was in fact correct.

[Cox International]

Could be.

Ronald Valentine measured it at 7-40 but that can't be right.

It may have something to do with pitch.

Matt is the one that has the tap and he is running some tests.

Bernie

[EXModelEngines]

Yes, as Bernie mentioned any concrete information would be appreciated.

I have a few more test to do with the current taps to see if it is a pitch issue on the thread.

Matt

[Admin]

Did you try asking MECOA? I notice they have the plastic ones, perhaps they know or can find out from the molds and or taps used to put the threads in them.

[Big Al]

I measured mine and would wager it is 11/64-40. Cox liked to use fractions, such as the .049 cylinder/crankcase (also glow head) 17/32-40.
Al

[Cox International]

Hm, intersting Al, and thanks. I never thought this in fractions. The 010 is .125 on the drawing and the 049 is .25.

I will try the size you mention.

Thangs again.

Bernie

[nitroairplane]

[quote="Cox International"]Could be.

Ronald Valentine measured it at 7-40 but that can't be right.

It may have something to do with pitch.

Matt is the one that has the tap and he is running some tests.

Bernie[/quot

That is odd because Valentine is a very precise buy and I think if he can make a nano bee with a 0.0006cc displacement he caneasure a thread because you don't make tiny doesn't with great parts fit by making sloppy measurements.
Is it possible that different people have different ones?

[fit90]

I would give the pitch of the threads some serious consideration. A lot of aviation use hardware has a different pitch to the threads than good ole SAE stuff. I think it was something like 37 degrees versus 45 degrees. Also, thread pitch was different on aluminum than on steel hardware in many applications. This helped the threads to "roll over" and seal lines. It also made a lot of hardware one use only. These may seem like minute differences, but at this fine a thread it makes a huge difference.

Good luck,

Bob

[EXModelEngines]

I would give the pitch of the threads some serious consideration. A lot of aviation use hardware has a different pitch to the threads than good ole SAE stuff. I think it was something like 37 degrees versus 45 degrees. Also, thread pitch was different on aluminum than on steel hardware in many applications. This helped the threads to "roll over" and seal lines. It also made a lot of hardware one use only. These may seem like minute differences, but at this fine a thread it makes a huge difference.

Good luck,

Bob

Bob,

Yes, very true. A custom tool may be necessary.

Matt

[fit90]

There is a gentleman on ebay that may be able to help. If memory serves me correctly he went by ridenfligh and his first name is Mark. I have dealt with him before and he is a super guy. He makes and sells the aluminum venturi bodies for Tee Dees. I think that Reggie used to carry these parts also. I am going over to ebay to see what I can drum up.

[fit90]

It took me a while because I had to search through all the really cool stuff from Xenalook but I found that he does indeed go by ridenfligh. As I said before, he is a really great guy and his products are exceptional. Perhaps he can help, maybe even supply you with some really cool after market stuff. Another avenue you may wish to explore would be machine shops that deal with aviation related hardware. When I get to work tomorrow I will check to see if I still have any names and numbers to machine shops that produce aviation hardware.

Bob

[Admin]

Yes, ridenfligh (Mark) is a great person to deal with!

[Cox International]

Forget Mecoa. This was a fateful relationship and we parted company due to ethical concerns. Don't really want to speak with this "gentleman" again, ever

Ridenflyhigh, that's Mike. Asked the question (via email) and never got an answer. I guess he is trying to protect that info lol.

No worries, we are on the right track now and I think we have it figured out

Bernie
www.coxinternational.ca

[nitroairplane]

Forget Mecoa. This was a fateful relationship and we parted company due to ethical concerns. Don't really want to speak with this "gentleman" again, ever

Ridenflyhigh, that's Mike. Asked the question (via email) and never got an answer. I guess he is trying to protect that info lol.

No worries, we are on the right track now and I think we have it figured out

Bernie
www.coxinternational.ca

So thats why you don't carry MECOA diesel heads

[fit90]

Bernie,

I just talked to a friend who is a machinist and he began listing many different types of threads. He did suggest looking in "The Machinist's Handbook" for the different types. It was a real learning experience. As much as I enjoy learning new things it is often times a little scarey because every one thing I learn also tells me that there are many more things yet to learn.

Good luck,

Bob

[warrenlead]

Hi Bernie

I did this once before for someone else... but forgot where. It's 2AM here, I just upset the mrs cos I got out of bed and went to the garage to check. lol

The .010 venturi is 5-40. This can be checked/confirmed by using a Cox 049 prop screw which we know is 5-40, (or 0.125" x 40 tpi) and screwing it into a 010 carb body.

The 020 on the other hand measures 0.167" x 40 tpi which is a hair bigger than a 8-40 bolt (0.164" dia.) so a tap for an 8-40 bolt would suffice, remembering that the venturi will need to be a tight screw in fit. You could confirm this for yourself by gently screwing an 8-40 bolt into a 020 carb body.

I hope this helps.

Cheers

[Cox International]

Thanks Warren,

I have the 010 drawing and the correct thread is .125 - 40 according to the drawing (which may represent #5, dunno).

An 8 - 40 thread might be suitable for a Delrin carb body but I'm not so sure that will work well with an aluminium carb body. Matt bought the 8-40 tap and it did not feel right when trying to screw it in.

11/64 -40 sounds about right and I just emailed Larry Renger; perhaps he knows?

Bernie
www.coxinternational.ca

[warrenlead]

Going by this chart, http://www.csgnetwork.com/screwnummachtable.html, 0.125 is #5

#8 is 0.164
the venturi measures 0.167
11/64 is 0.172

So the 11/64 will be 5 thousandths bigger. Might be a bit too loose but I can see your dilemma. The smaller one #8 would be fine in plastic/Delrin but probably too tight for aluminium.

Cheers

[EXModelEngines]

Going by this chart, http://www.csgnetwork.com/screwnummachtable.html, 0.125 is #5

#8 is 0.164
the venturi measures 0.167
11/64 is 0.172

So the 11/64 will be 5 thousandths bigger. Might be a bit too loose but I can see your dilemma. The smaller one #8 would be fine in plastic/Delrin but probably too tight for aluminium.

Cheers

Warren,

Yes, I tapped 8-40 in both delrin and aluminum. You could use a wrench and screw it into the delrin (albeit pretty tight). When I did the same thing with the aluminum it was too tight, as you mentioned.

Regards, Matt

[Cox International]

Sooooo.. could it be the 7 - 40 that Ronald Valentine measured? I'll call him again today.

If I could only find teh darn drawing lol.

Bernie

[warrenlead]

I don't think there is any such thing a #7-40 and if there was it would be too small. You're after something like an 8.5-40 which doesn't exist either.

The closest one is the 11/64 -40 TPI which I think is worth a try.

Cheers

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