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hair-pin needle-clip-DIY

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hair-pin needle-clip-DIY

Post  roddie on Sun Jun 04, 2017 9:00 pm

Here's an idea that I thought-up in the last few days. It uses a common hair-pin (Bobby-pin) to make a clip for a needle-valve stem/shaft. It's applicable in this particular example to Cox 1/2A reed-valve engines. Its main purpose is to hold the needle-setting from drifting. Sleeves of silicone fuel-line are used for retainers. The loop on the hair-pin serves as the mount.

This is all it is... I'll show a mount example below.



There are two types of "Bobby-Pins".. We'll call this type the "open-type". The "closed-type" were what I originally perceived for this.. but the clip-arms are too-close together.

A "Closed-type" example..



The above "closed-type" didn't work-out. The hair-pin must be cut shorter if running the cylinder-orientation in the same plane as the needle. I used "vise-grip" locking-pliers having a wire-cutter to shorten my example.



Note the gallon-size freezer-bag. It's plenty-big for inserting cutting-pliers.. and containing small fragments/parts that might otherwise catapult into oblivion when sheared. It's also a second-safety to protect your eyes.

Once shortened.. here's what it looks like on a Cox .049 product-engine with horseshoe-backplate.



Here's the hair-pin mounted to an engine-stand with that same engine.



That could just as well be the nose of a model-airplane. The hair-pin only needs a single anchor-point at its' loop. I used a small screw/washer on my bench-mount.. but the loop affords itself to other methods of attachment. A blob of epoxy.. Laughing a small capped dowel-pin... or on new-construction; a point/location that will suit the engine-installation.

I've had issues with needle-float.. running both; stock and modified needle-springs on horseshoe back-plates. Coiled compression-springs can recoil "radially".. and augment a needle-setting.. especially if the spring "grabs" on something.. It's then "pre-loaded" to recoil radially. Engine-vibration would no-doubt hasten that

Friction-collars for needles are nothing new.. so why not try to adapt them to any engine?



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Re: hair-pin needle-clip-DIY

Post  NEW222 on Sun Jun 04, 2017 9:13 pm

Great idea, but is it just me, or does anyone else have any trouble with seeing pictures?
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Re: hair-pin needle-clip-DIY

Post  roddie on Sun Jun 04, 2017 9:31 pm

NEW222 wrote:Great idea, but is it just me, or does anyone else have any trouble with seeing pictures?

I've seen images rotated the wrong way................... hurts my brain. I pray for the "mods" to fix them!
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Re: hair-pin needle-clip-DIY

Post  NEW222 on Sun Jun 04, 2017 10:49 pm

Its late here now, but I now see the pictures and it looks good. With the better half a hairdresser I may have to try this . Thanks for the great idea.
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update on clip application.

Post  roddie on Mon Jun 05, 2017 2:30 pm

NEW222 wrote:Its late here now, but I now see the pictures and it looks good. With the better half a hairdresser I may have to try this . Thanks for the great idea.

Thanks Chancey! I made some discovery that's worth mentioning. The previous open-style clip-example fits the product-engine's needle shaft well because the shaft is 3.18mm diameter. The gap between the clip-arms is approximately 4mm. The silicone tube-sleeves pinch the arms together with good clamping force.

I had abandoned the closed-style clip application.. but now find it works very well to clamp the smaller shaft-diameter of a Cox tanked-engine's needle. See below.. a Cox Babe Bee .049.



There's already sufficient clamping-force without putting a sleeve on the open-end. There's also about 1/4"/7mm more distance between the needle and the engine-cylinder than the product engines' horseshoe back-plate. This distance obviously becomes a non-issue if orienting the cylinder in a different position (IE; 90/180 degrees) from the needle.

Another interesting feature between the closed and open-style bobby/hair-pins, is that the closed-style has 4 detents.. and they're only on one arm of the pin. The other arm is straight. The open-style only has 2 detents.. but has them on both arms.. equidistant.




I figured that this was worth mentioning. If you search Google-images for "hairpins"... you'll see a myriad of shapes/styles.. but these two referenced in this thread, are generally the more common types. I was lucky.. in that my stepdaughter had some of both types.

The closed-type "will work" on smaller-diameter needle-shafts.. and would likely work well on a Cox Pee Wee .020 engine. It takes a good amount of force to spread the arms apart on the closed-style hair-pin. I used a small flat-blade screwdriver to spread the arms.. while installing the "clip" on the .049 tanked-engine's needle.

Take into account.. the hair-pins are spring-steel. Use caution when cutting/shortening them. As I mentioned.. I sheared them with the cutters in the jaws of my Vise-grip locking pliers while inserted into a plastic bag. A better way would be to clamp the hair-pin in a bench-vise.. and cut them abrasively with a dremel/cut-off wheel while wearing safety-glasses.

There is a coating on these hair-pins. It's some type of plastic or resin. This doesn't seem to interfere with the function for these applications.. but if able to be removed.. the hair-pins should accept solder. This would only be required on the loop-end.. where a bracket might be soldered. This could be valuable for fashioning a custom clip stand-off for other engines. Something of an L-bracket with hole to mount under a screw-head on a Cox Medallion, Tee Dee.. or any other beam-mount/front-rotary engine that could use some needle-stabilization.


Last edited by roddie on Mon Jun 05, 2017 3:48 pm; edited 3 times in total (Reason for editing : application)
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Re: hair-pin needle-clip-DIY

Post  getback on Mon Jun 05, 2017 6:46 pm

Good info man , looks like it would work just fine if application needed did'nt know there were so many difft. kinds of Bobbys Shocked But you would sure bee careful cutting them !! Most the time the application of a new seal on horse shoe back plates work IF the threads are not worn too bad or the fuel line for a seal at the needle will keep the needle stable if applied right ..... This is good but if the needle is turning it is loose,,  the spring is sprung or the wrong one ?! On these springs they should NOT let the needle move the way they're made being rounded at both ends with the edges turned in ..

Of course i looked through their inventory and some DO look like they would do some digging into the back plate and make a groove == You could file down the edge of the spring end so it would rotate if needed ?? Eyebrows Beer Cheers
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Re: hair-pin needle-clip-DIY

Post  roddie on Tue Jun 06, 2017 9:29 pm

getback wrote:Good info man , looks like it would work just fine if application needed did'nt know there were so many difft. kinds of Bobbys Shocked But you would sure bee careful cutting them !! Most the time the application of a new seal on horse shoe back plates work IF the threads are not worn too bad or the fuel line for a seal at the needle will keep the needle stable if applied right ..... This is good but if the needle is turning it is loose,,  the spring is sprung or the wrong one ?! On these springs they should NOT let the needle move the way they're made being rounded at both ends with the edges turned in ..

Of course i looked through their inventory and some DO look like they would do some digging into the back plate and make a groove == You could file down the edge of the spring end so it would rotate if needed ?? Eyebrows Beer Cheers

I'm glad you replied brother. Worn parts should be replaced if possible. This clip design can function as a secondary stabilization for the needle-setting.. worn or new. The weight of the components is negligible. You have to source a hair-pin though... Laughing

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