OS105HZ-R Ring Pin

[Delarado]

Guys,

The ring locating pin on my OS105 has disappeared - how comes?

Ive never changed the ring or liner - Just the rear bearing once. Do they just wear out over time? Id estimate the engine has had 25-30 gallons through it.

What can I do now, do I need a new piston?

[hedge]

Funny enough I've just done the bearings in mine and lost half the pin... The other half was embedded in the top of the piston!! with only half gone I will continue to use this set up. If the whole thing has gone then the risk is the ring turns, the open part of the ring meets one of the open ports on the liner and boom. I'm emailing OS as I have heard of a few people getting this, my question is how do I prevent it happening again.

[hedge]

Email: mail@ripmax.com apparently you need to go though the UK distributor.

[Delarado]

Ive mailed them.

[waveydavey]

I got a very good response from Ripmax but I went through Japan. A guy called Pete Halman called me and in fairness took the engine from me and repaired it with new bits. I linked to various threads on this and I haven't heard that OS have done anything about it.

I've even tried repairing one and got a flight out of it. However, I have a theory. Once the wear starts this is happening throughout the engine and I think the con rod allows the piston to rotate slightly effectively rubbing the pin against the ring, the holes in the piston make sure the ring is tight and forced against the liner not allowing it to turn. It's a very small c lock pin with a 0.1 wall thickness or something so takes no effort at all to damage. The result is as you found the ring turns and ends up in one of the ports.

My solution was to replace the con-rod at the same time as the piston and ring, and touch wood I've had around 40 to 50 flights on it and it's okay. I've got nothing scientific to back it up though just a hunch

[hedge]

I knew I had read about it before, did they recommend anything?

[Delarado]

Dave, agreed that may be part of the reason, however my engine has never had anything changed except the rear bearing when it got notchy. So unless its just general wear and the con rod should be changed every 10 or so gallons as a matter of course? (Which would suck)

Do you have the address that you wrote to?

[Delarado]

For completeness sake Dave I've only just had the engine apart after our PM conversation when you suggested changing the con rod a few months ago to avoid the pin wear! Its been running fine up till now, Ive just pulled it apart as it's probably due a refresh. I have the new ring and con rod sat next to me ready to go in but I don't want to reassemble it before I sort out this piston pin issue!!

[waveydavey]

I think that's the problem though Carl, we put hundreds of flights on an engine and just change the bearings even though other parts such as the crank and con rod are being worn the more flights you do. I've just changed my first bearing since the rebuild and it all looks okay and the con rod is still tight. I'll start counting again from now and see where I start to have issues. It's been reported once it's happened then it doesn't take long for it to occur again which is why I think it's down to other wear.

This is Petes email, peter_halman@ripmax.com a very nice man and helpful. I'm sure he won't mind me letting you have his email

[waveydavey]

I knew I had read about it before, did they recommend anything?

No although Pete did say he would speak to OS and see what they thought about it. I think we've just got on and replaced bits as and when. When mine went the 3rd time after 30 or so flights I thought it was time to take it further. I emailed OS direct and within a day Ripmax had contacted me.

[hedge]

Great feedback, I am around 180 flights this is the first issue i've had, roughly 3 bearing changes in that time and each time its fine. I can live with having to replace the con rod at this stage but every 50 would put me off.

[Flat Eric]

What parts are they replacing to fix the issue or has the piston been modified now? I have 3 105's and they will be needing serviced soon.

[waveydavey]

I'm not sure they know Eric or whether OS have acknowledged the fault. The wear on the con rod is my hunch and is the only other thing in the line that wears. The crank does wear but the crank pin shouldn't, a new con-rod is £18 so well worth changing with a major service or every 100 flights or so.

I'm sure with a couple of emails OS will get the message and take a look at the problem. In fairness to Ripmax they replaced the damaged parts and I added a new crank and con-rod to the list. So in effect a new engine apart from case for under £100

[Delarado]

Ive made a post on Helifreak

OS105 Piston Pin Wear - HeliFreak