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Post  aspeed on Mon May 25, 2020 8:14 am

balogh wrote:It is the 3D nipple body with sufficient thickness that, combined with the brass nipple, will last much longer than the stock COX  RC nipple. When the fuel stub breaks off - and it will sooner than later- from the stock part, there is no way to replace it with a threaded brass nipple because the plastic sleeve is very thin.
Oh, OK, I do not have one to be able to comment on it then. There is usually a plan B though if you think hard enough. I have snapped a few plastic nipples off on LAs, and Thunder Tiger .07s just bumping them with starters and being careless, as well as cheap swap meet deals.
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Post  balogh on Mon May 25, 2020 8:30 am

The Tarno RC carb had a similar concept for the fuel nipple, with the whole spraybar unit including the nipple body made of brass...


Ball bearings you say? 3D printed BB crankcase.  - Page 2 Cox_td10

if one wanted to re-purpose it to a COX TeeDee RC carb, the spraybar hole on thr nipple body had to be widened to accommodate the COX spraybar..once I tried it with a used and defunct Tarno carb, but unfortunately cannibalized the all-brass nipple body and have given up...


Last edited by balogh on Mon May 25, 2020 8:33 am; edited 1 time in total
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Post  Jason_WI on Mon May 25, 2020 8:32 am

I was wondering how long it was going to take for that new carb fuel inlet to be spotted. I accidentally left it on the carb when it took the picture. I had one crumble when it was installing a carburetor and thought there must be a better solution.

The brass fuel barb is 3-56 threaded one from Clippard. The barb is too small for regular size .049 fuel tubing and only works with the .010/.020 fuel tubing. They are also almost $1 a piece too.
I did approach Matt and he is also working on an alternative solution.

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I also tried to do a direct print of the entire part. Being so small I can’t get fine enough detail on the barb fitting. I might be able to change the design of this so the barb comes out round vs oval. This prints as an overhang so I would have to teardrop shape the barb for it to come out round on the 3D print. This would also require a lot of cleanup work where just tapping a hole would be easier with a threaded nipple.

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Post  balogh on Mon May 25, 2020 8:40 am

Jason if the problem is only the size of the fitting fuel tubing, then what I would do is attach an 010 or 020 size, short  fuel tube to the nipple so that the barb will hold it, then pull the larger, 049 size fuel tube over the other end of short 010 size tube, and  run it up to the 049 engine...I may also pull a small spring - the one used in Babe Bee tanks - into the 010 size tube to prevent it from collapsing under the external pressure by the 049 tube..or would just add a copper or aluminum tube connector in between the 010 and 049 tubes etc...

My garage-tuning solution, not ultimately professional, but would still be working with your small nipple, and be several orders of magnitude better and more reliable than the all-plastic COX fuel nipple...I would still be interested in buying such a hybrid solution...
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Post  Jason_WI on Mon May 25, 2020 8:54 am

These fittings would fit the .049 size fuel tubing but have a painfully slow shipping option.


https://m.aliexpress.com/item/32696220692.html?trace=wwwdetail2mobilesitedetail&spm=2114.12057483.0.0.2d50546d9TXC5Y

They are for pneumatic hose but should work fine. They will be larger than the Clippard 3-56 version.

I made the fuel inlet thicker for more strength. I tried to crush a glass filled Zytel Version with my fingers and could not even get it to deform it’s that strong. I need to test it with fuel to make sure there still isn’t an issue with leaks.
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Post  balogh on Mon May 25, 2020 8:57 am

Good to see that you will soon find the solution !!! I believe the small nipple size is just cosmetics, if the larger size is difficult to source, I would still happily compromise on the small one...we are modelers anyway and need our part of innovations when completing our fuel systems on our planes.. Smile
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Post  1/2A Nut on Sat May 30, 2020 1:04 am

Any word on the threaded insert?

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Post  Jason_WI on Sat May 30, 2020 1:50 am

They came in today. I need to update the drawing to make the screw boss bigger and enlarge the hole size. Backplate will be updated as well. 5/8-18 Bottom tap came in also but I need to take the first 2 tapered threads off of it on the grinder.

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Post  1/2A Nut on Sat May 30, 2020 2:40 am

More tweaks but eliminating the potential of stripped screw holes is worth it.

I have set up the 65 deg carb mount with a Killer Bee .049
Will be bench testing the throttle function and peak power
with the APC 4.4x4 labeled as a .049 Free Flight Prop.

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Post  getback on Sun May 31, 2020 8:21 am

Well that makes more since , i was thinking it had something to do with the cly. placement But didn't want to sound stupid and say something about the size of the insert >> guess i missed a line . Looks good Brad why is it U use .020 spinners on .049 engines again ( i am having brain farts i guess ) lol!
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Post  1/2A Nut on Sun May 31, 2020 10:44 am

Less mass out at the end of the driveline for less wobble, reduced heat and increase in rpm.
Helps to center the prop / insets a bit and allows the use of a E starter.
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Post  getback on Mon Jun 01, 2020 7:47 am

Thanks Brad , makes since to me Very Happy
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