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HomeRC & Power✈️Aircraft🚁HelicopterEngines Plugs Mufflers Fuel › Repair a stripped glowplug
03-03-2020 07:54 PM  32 days ago
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ticedoff8

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Morgan Hill, CA. USA

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Repair a stripped glowplug
I have a YS 120SR-X head whose glowplug hole is pretty much stripped out.
Please don't judge - I didn't do it.
So, how do I fix it?

There used to be a heli-coil kit that could be used to repair this - does it still exist?
Is there someone that repairs this kind of damage?

It is $40 USD to buy a new one (RC Japan) + shipping
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03-03-2020 08:10 PM  32 days ago
Rojoalfa

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It is a big motor so the solution is more easy to do.

You need to do a "sliding sleeve" threaded from inside with a boss in one end.

Open a bigger hole removing the thread in fail and install the "sliding sleeve" from the lower part of compression top. This has to be done with heat.

Let me do a drawing...

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03-03-2020 08:13 PM  32 days ago
banshee rider

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google is your friend

https://www.google.com/search?q=rc+...chrome&ie=UTF-8
ageing is manditory maturity is optional
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03-03-2020 08:30 PM  32 days ago
Rojoalfa

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Ok... You need to make a sliding sleeve with thread inside to install the glow plug.

This sliding sleeve has to have a boss to install from the inside.

Reassembly compression top with this sliding sleeve installed. Put the glow plug.

This job in my country is cheaper than to buy a new compression top.

Probably in your country is cheaper to buy a new one.

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03-03-2020 09:31 PM  32 days ago
whirlyspud

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USA

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03-03-2020 09:59 PM  32 days ago
ticedoff8

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NewEgg: https://www.newegg.com/p/302-009T-00818
$27 + $9 shipping.
"Recoil 34040-32 Standard Thread Repair Kit, 1/4-32 UNEF, Inserts [1.5D] 10 Pc (1 PK)"
I may want to try that, but I still don't know how hard it is to do it right the 1st time.
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03-03-2020 11:13 PM  32 days ago
JuanRodriguez

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Clarence Lee the engine designer (California ??) had a service where he would repair a stripped head ..... don’t know if he is still doing it or if he is even still alive..... you may want to google his name to see ....Been there, done that and old enough to know better.....
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03-04-2020 12:21 AM  32 days ago
ticedoff8

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JuanRodriguez Clarence Lee the engine designer (California ??) had a service where he would repair a stripped head ..... don’t know if he is still doing it or if he is even still alive..... you may want to google his name to see ....
He used to be in Sunland, CA
But, he is in his 90's at least.
He was the 1st one I thought of.
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03-04-2020 01:25 AM  31 days ago
wjvail

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The first option would be to have Clarence Lee do the work. He has done these for years and the heads I've seen were really done well. I have a head somewhere around here he did 30 years ago. Check out page 133 of this month's Model Aviation. I've also uploaded the picture below if you don't get the magazine. It's not the best picture I've ever taken but I think you can still read it.

If you think you and your friends might be doing more than one of these, consider buying a ReCoil kit. I've repaired a few heads over the years. If you choose to put in a "helicoil" yourself, just be careful when doing 4 strokes. Very often the valves can get close to the glow plug hole and you will obviously have to drill the hole oversized to tap it and thread in the insert. If at any point you nick the valve seat, you're done.

I know it all sounds like a hassle, and it is, but the upside is that you will end up with a head with steel threads.

https://www.ebay.com/itm/Recoil-340...m4383.l4275.c10

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03-04-2020 01:47 PM  31 days ago
Rojoalfa

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This beauty deserve it.

A huge cylinder cover...

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03-04-2020 02:23 PM  31 days ago
whirlyspud

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USA

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I repaired the threads on a ys 45 airplane motor years ago with the recoil insert. I probably still have the kit somewhere. It was easy as tapping the hole and I had to cut a couple threads off of the coil because it was a little too long.
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03-04-2020 02:37 PM  31 days ago
wjvail

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Large cylinder heads help somewhat but not as much as you'd think. I've flown models without the cooling shroud installed.

Some number of years ago I got into a lively debate about how much air cooling adds to our model engines. To prove a point, I taped off the fins of my OS .47 with aluminum tape. Since that might still provide some cooling, I wrapped the tape/fins with a cotton rag. Finally, since the cotton rag might let air through, I wrapped to fins/tape/rag with plastic wrap.

While it wasn't possible to completely lean the engine to its maximum peak, it ran just fine very close to max power. RPM was withing 500 of its maximum and temps stayed below 200F.

So the goofy large cylinder heads YS has put on some of their engines might make you feel better, but they aren't as important as you'd think.

Watch at YouTube

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03-04-2020 04:09 PM  31 days ago
Rojoalfa

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Very interesting point.

According to your observations, the cooling factor of FINS are not related directly to air flow condition.
So, in helicopter motors, the FIN design is working for area of radiation.

Conduction and Convection are a secundary mechanism.

So, the bigger cylinder head mass, the better...

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03-04-2020 06:49 PM  31 days ago
ticedoff8

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Morgan Hill, CA. USA

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I have no fixed wing planes now. I am 100% helicopters.

I would imagine that the fins on the head of a fixed wing engine (with the smaller head) are mainly for show.
When you look at a small fixed wing engine (like an old OS 47), the head is small, it runs on 12% oil and (maybe) 15% to 20% nitro and is not typically running at its peak tuning (always a little fat). A lot of times, the wrong prop is used, so the engine is nowhere close to its maximum RPM while in flight.
Besides that, a sport fixed wing motor is not considered "high performance" either.
So, if you run a fixed wing sport motor rich, it is generating lower combustion temperatures and most of the heat is leaving in the oil and unburnt fuel out the muffler (in your picture, you have a very restrictive muffler with no performance benefits but it is adding mass and acting as an additional heat exchanger for the engine).

I would completely disagree with your conclusion on a dedicated helicopter engine in a high performance application.
They run 20% oil (oil carries away heat) and max out at 30% nitro.
They have to be tuned to provide maximum power (so they are 1 click away from being too lean) and use the best "tuned pipe / muffler" that can be found (tuned pipes help scavenge the exhaust and provide a cleaner incoming air/fuel mix for more power - and more heat).
And, their engine mounted fan is enclosed in a shroud that carefully directs the airflow to upper portion of the cylinder / head. There is practically no airflow to the lower portion of the crankcase.
They also run at a fixed RPM and vary the torque to provide power changes. The RPM is always close to the maximum RPM rated for the motor by the manufacturer. So that takes away the variable that the wrong prop introduces.
I wish I could get my YS 120SR-X to maximum performance at 200F.
My on-board telemetry (the sensor is mounted on the head's glowplug boss) shows 250F to 310F on a typical flight. If it is less than 200F, I know it is too rich and something is wrong.

So, I would suggest you may want to run your same experiment with an OS 55HZ-R on a Synergy n556 with fuel that has 21% oil and 30% nitro and tell us how well that worked out for you.
And fly it like you stole in both parts of the test.

Now, before this gets too far off track:
I found there may be hope.
The glowplug hole looks like they cross-threaded a plug and forced it in 1 or 1 1/2 turns. A new plug will not even start threading properly from the top.
But from the inside of the head's combustion dome, I can get a new glowplug to thread in easily for about 2 turns, then it jams.
If I can chase the threads with the tap (from the inside out), there may be enough meat left to hold the glowplug.
I bought a 1/4" x 32 tap on Amazon and I should have it tomorrow.
If (after I chase the threads) I cannot torque the glowplug down tight enough, I'll just get a new head. It is $40 USD to buy a new one (RC Japan) + shipping (YS Part number: S3102. RC Japan: ¥4,214.
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03-04-2020 07:26 PM  31 days ago
ticedoff8

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Morgan Hill, CA. USA

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The first option would be to have CLarence Lee do the work. He has done these for years and the heads I've seen were really done well. I have a head somewhere around here he did 30 years ago. Check out page 133 of this month's Model Aviation. I've also uploaded the picture below if you don't get the magazine. It's not the best picture I've ever taken but I think you can still read it.
I agree. I should have checked the back pages of the AMA mag.
I didn't think he was still doing this.
His address and phone number hasn't changed in 30 years (lol)

I don't think I want to invest in the kit.
It is much less trouble and cost to simply buy a new head.
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03-04-2020 09:11 PM  31 days ago
main rotor

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Pomona NY USA

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if you take an old glow plug and use a thin cutoff disk and slice the threads length wise in a few places you can make a thread chaser.A tap may make the hole bigger than what you have now
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03-04-2020 09:52 PM  31 days ago
ticedoff8

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if you take an old glow plug and use a thin cutoff disk and slice the threads length wise in a few places you can make a thread chaser
I've tried that before when I didn't have the patience to find the correct tool for the job. But, usually it does not end well.
A tap may make the hole bigger than what you have now
How would that happen?
A 1/4" x 32 tap is the correct tap for a glowplug.
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Believe 1/2 of what you see and none of what you hear.
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03-05-2020 12:23 AM  31 days ago
main rotor

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Pomona NY USA

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A tap because its designed to cut will do just that , cut the damaged area away. A thread chaser , which is basically what you would make from slotting an old glow plug ,will push the metal back into shape
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03-06-2020 11:00 PM  29 days ago
ticedoff8

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Morgan Hill, CA. USA

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A tap because its designed to cut will do just that , cut the damaged area away. A thread chaser , which is basically what you would make from slotting an old glow plug ,will push the metal back into shape
I used a 1/4" x 32 plug tap and it worked out as well as I hoped.
There were enough threads on the combustion dome side to get the tap started. It took a few starts to get all 4 sides of the tap to line up and be square to the hole, but then it was just a matter of gently turning the tap and feeling it bite a little, then backing it, then turning to bite some more.
The plug threads in with no problems and torqued to my SAE Calibrated and Certified wrist.
I think with the copper gasket, it will seal ok and I'll know in a week or so.
I hate to say this, but after flying nitro for the last 40 years, I finally bought a 1/4 x 32 tap.
Now, I think I'll get a 1/4" x 32 die, just in case I need to chase the threads on a plug.
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Believe 1/2 of what you see and none of what you hear.
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