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Heli clutch advice

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Jon - Laser Engines19/06/2019 14:31:09
4664 forum posts
173 photos

A customer has returned the Laser 70 from his helicopter to me for service and in the process of sorting it out i have observed signs of slip and heat build up in the clutch shoes. Sections of the steel shoes are brown/blue as the heat has coloured the steel. Given the heat required to do that i do suspect excessive slip in the clutch.

Not being fully versed in i/c heli clutches i cant say for sure if its in need of new clutch material or if its ok. Given the faff required to change it after the engine is repaired i am keen to try and do it ahead of time if it is decided that its shot.

I can upload photos later to aid diagnosis

Denis Watkins19/06/2019 14:40:39
3682 forum posts
173 photos

With respect to the owner Jon, this usually happens with the novice, just lifting then not, then lift then down.

The metal linings work by friction

Less obvious wear with the accomplished heli pilot

As they fast idle to get the motor warm, then smartly into the air

So far far less slipping

Jon - Laser Engines19/06/2019 15:11:52
4664 forum posts
173 photos

This setup has some sort of clutch material, its not metal on metal. I have seen them in the past as we used to sell new liners for hirobo clutches when i worked at a model shop. This liner is much thicker though and i cant see a join line so it might be a non replaceable item :\

As for the owner, i think he got the whole lot 2nd hand so no worries there.

Peter Christy19/06/2019 18:04:58
1434 forum posts

Does the clutch liner look OK, Jon? And do you know the make of heli? It ought to be possible to get a replacement liner.

The main issue is that if its a thick liner, and excessively worn, the shoes bend out more and eventually break. Have a good look for signs of cracking along the "hinge" point.

--

Pete

Jon - Laser Engines19/06/2019 23:01:33
4664 forum posts
173 photos

It is a robbe heli of some flavour. We did a few of these heli engines in the early 90's but they were never mass produced and the clutch side was not done by us. Given the age i really doubt spares are available.

As for the liner, i will grab some photos tomorrow. There is no apparent cracking on the shoes but my eyes lack NDT capability so anything could be going on inside. The gap is also not excessive but the surface looks a little sad in my view.

Again though, i am not exactly sure what constitutes normal wear and what is shot. i know that on my model cars if the clutch bell turns blue it means you broke something!

Peter Christy20/06/2019 08:37:39
1434 forum posts

Jon,

Give Keith Wallinger a call at Robbe-Schluter UK. You might be surprised at the amount of stock they've got! I managed to get spares for a Schluter HeliBoy that well pre-dates the Robbe helicopters!

If you can't find contact details, try Midland Helicopters, who are next door and part of the same group.

--

Pete

Jon - Laser Engines20/06/2019 09:13:25
4664 forum posts
173 photos

It was Midland/Dick wallinger that did the conversions in the first place. They were on my list of people to call today!

Peter Christy20/06/2019 09:48:37
1434 forum posts

Yes, I remember Dick Wallinger flying a Robbe Mosquito that he'd converted to 4-stroke at one of the Schluter Cups! He managed to get it through to the fly-offs, where he had to do part of the F3C aerobatic schedule!

The final manoeuvre was an auto-rotation, which we all knew was going to be interesting as he didn't have an auto unit on it!

Despite the added weight of the 4-stroke in a relatively small model, he actually pulled it off - even managing the auto without damaging it!

He got a huge round of applause, but not too many points! I think he was just happy with the moral victory!

laugh

--

Pete

Jon - Laser Engines20/06/2019 12:11:41
4664 forum posts
173 photos

after much hassle and trying to get more than 0.1mb/s upload out of our useless internet i gave up and used my phone as a hotspot so i could upload the photos.

c1.jpg

c2.jpg

c3.jpg

Peter Christy20/06/2019 13:46:34
1434 forum posts

Well,I've seen a lot worse than that! I think I've probably flown with worse than that, but not in a while! wink

The straight lines between the clutch shoes and hub look pretty parallel, so the wear can't be that excessive. How much clearance is there between the shoes and the lining? It doesn't need to be much.

It does look as if only about half the width of the shoe has been touching the liner, which could explain why its been getting hot. Is there a step in the liner between the "burned" and unmarked sections?

It could be that there has been a slight mis-alignment in the clutch, causing the uneven wear. What are the bearings like?

I've never owned a Robbe heli, so I can only go on my experience with other types. However I reckon there's a good few hours left in that yet, but its probably worth a phone call to Keith to check and see if he's got spares.

--

Pete

Jon - Laser Engines20/06/2019 13:52:15
4664 forum posts
173 photos

I had a chat with midland and his comments were similar to yours. It seems to be ok but i just wanted to check before i sent it and the engine back to the customer as an airworthy unit. Its all well and good me fixing the engine but if the clutch gives up its game over anyway!

Denis Watkins20/06/2019 14:25:26
3682 forum posts
173 photos

You know the clutch unit could be near 20 years old Jon

Though looking at the lining, it was virtually new when last used

Again, my comment, that a novice tempered that brown and blue on the steel

With multiple tentative lifts

It looks as if that assembly barely flew,

Peter Christy20/06/2019 15:12:15
1434 forum posts

If it was me, I'd just put it back and carry on flying with it! But I would have a look at the alignment when I re-fitted it. It does look as if it has been running slightly out of true.

As I said, probably worth checking the bearings, but I don't reckon it will give up any time soon.

--

Pete

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