What needle is this? w/pic

Thanks for the info, Roddie.
Now that I know what hey are, maybe someone can use 'em.

My pleasure Terry!

The backplate that you have there, is the Cox "Postage-Stamp" type.. and its needle has a custom-knob fitted to the top. Those backplates were usually orphaned/discarded once the model that utilized them broke.. because they fit into a slot.. and had no other type of mounting-provision. Carl Goldberg models made an adapter to use that backplate/engine on a standard radial-mount plywood firewall. Sometimes they show-up on eBay.. but have long been out of production.

It does however have a very desirable fine-thread NVA... and many modelers extract the NVA for use in other engines where they need extra-fine resolution/fuel-mixture control.. such as with a pressure-bladder system.

These backplates were fitted to Cox's early "product-engines" (#'s 190/290) "290" being a seperate "off-the-shelf" replacement engine for a model that originally came with the 190.. from what I understand. There's threads here on the forum.. that are quite interesting reads.

You seem like a guy who enjoys "tinkering".. so I'll include some info on how I made my own 2-piece mounts for running that backplate and superb needle on an airplane. It merely requires a little measuring.. and making two Z-bent metal plates with holes drilled in the right places.



Those are .040" sheet-aluminum plates, cut and drilled to match the 17/32" spacing of the 2-56 case-screws without any modification to the plastic backplate itself.

You could run that backplate on your GB... with the fuel-tank/system of your choice if you wanted.

Some interesting comparison photos..





Adapter-plates "can" fit the standard vertically-oriented Bee backplate area on a firewall.



If you'd like, I can provide you with all the measurements. I mailed a few sets of these plates along with the proper length case-screws to a few members here on the forum. One member "Getback" (Eric) experienced a stress-fracture along a bend-point on one of the aluminum plates. I made these plates on a CNC router and also made bending-jigs to form the Z-bends. Eric's issue might have been an isolated condition.. therefor; a light-gage/mild-steel might be a better choice. It would come with a weight-penalty though.

Must be some atmospheric condition floating brain waves or sumpin', Roddie.
Just moments ago I was in my "shop" looking at that backplate, thinking it might/could replace the GB tank.
I have several sizes of old small Perfects, allowing better control over flight time and balance point.
And yes, I can and do tinker!
MOF, the pic with the ruler is enough to let me sort it out.
Veggie can will do for stock. I admit, the bends may take a few trials.
Thanks for the kickstart!

My plates measure .785" square.. with an on-center 7/32" 4-hole pattern. A rat-tail file can be used to trim the radius on one edge where the venturi protrudes. That edge receives the case-screws that tighten the backplate/gasket/case together.



The Z-bend is .25" from the edge on both sides. You can pad the jaws of an avg. bench-vise to gage the .25" depth for the bend.

I made fixture-blocks to be compressed in a bench-vise.





The 785" measurement is the distance between two parallel protrusions on the rear/mount side. Making the pair of plates "square" with the 1/4" bends.. just happened to work-out and still have ample clearance for the air-intake when mounted.

Nice work, Roddie, simple and neat - thanks for the clear pix too.
A "make-do" man after me own heart, no doubt.
"We don't need no stinkin' store-bought mounts!"

BTW, I was informed the needles also fit "a KK (?) spraybar for TDs".

Here is an alternative way to mount one of these engines, a little easier as it only requires one bend per mount. The thread is about an entire model, a "290 Special", the mounts can be seen at the end.

https://www.coxengineforum.com/t9988-i-couldnt-wait-anymore