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HelicopterMain Discussion › clutch gap
02-20-2014 02:23 AM  3 years agoPost 1
antja

rrApprentice

Levin new zealand

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can someone please tell me what is the right gap between clutch bell and shoe on vario petrol mechanics, cheers

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02-20-2014 02:28 AM  3 years agoPost 2
jschenck

rrProfessor

La Vista, NE.

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I don't have any experience with Vario but all the clutches I've setup including my Predator gasser I look for a clearance of .008" - With that clearance I don't break clutches. I I were building a Vario I'd look for the same clearance.

With any clutch I'm looking for a runout of less than .001" if possible but especially true with a gasser since the clutch is usually bigger and heavier.

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02-20-2014 03:54 AM  3 years agoPost 3
RM3

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Killeen, Texas - USA

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I run a clutch gap of around 0.060 to 0.080 inch...don't have any more issues with finicky requirements .

the biggest issue I see with the clutch is like JSC said...the runout...some clutches seem to favor one shoe over the other as well when I tried a "sharpie" test on some century clutches...

+++ on keeping the gap as tight as possible, that will help minimize cracking.

showing a preference will only get you into trouble, 90% of everything is crap...

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02-20-2014 07:16 PM  3 years agoPost 4
Four Stroker

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Atlanta

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Find someone with a lathe and bore out the liner to the jschenck recommended clearance AND check for less than 0.001" TIR at the clutch.

The bearings in the clutch stack have maybe 0.0003" radial clearance. What do you think happens when the clutch has 0.003" runout ?

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02-20-2014 10:17 PM  3 years agoPost 5
AirWolfRC

rrProfessor

42½ N, 83½ W

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I run a clutch gap of around 0.060 to 0.080 inch...don't have any more issues with finicky requirements
That's rather excessive and asking to break the clutch shoes off.
1/5 of that or less is more reasonable.

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02-20-2014 10:31 PM  3 years agoPost 6
Four Stroker

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Atlanta

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I'm sure that is a typo. Meant 0.006" ~ 0.008".

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02-20-2014 11:24 PM  3 years agoPost 7
RM3

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Killeen, Texas - USA

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not a typo...I'm done with managing tight clutch gaps...hopfully FOREVER!

Watch at YouTube

showing a preference will only get you into trouble, 90% of everything is crap...

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02-21-2014 02:40 AM  3 years agoPost 8
AirWolfRC

rrProfessor

42½ N, 83½ W

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That's some nice work.

But I wonder about the amount of shoe mass you have on the side of the pivot. It looks like maybe half of the original shoe. That means much less outward force, less friction for the same rpm. . . . Your new clutch may end up slipping.

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02-21-2014 03:11 AM  3 years agoPost 9
Four Stroker

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Atlanta

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Clutches long long ago were made like this - Kalt, Hirobo. The one piece clutch took over. Cheaper ?

You have the springs to play with to adjust the engagement rpm. I bet you could sell those to gasser flyers. Doesn't really need to be hardened (except for the springs) since it's not a spring anymore. I like it. Good CNC home product.

There was another guy with a CAD package redesigning the one piece clutch. Haven't heard from him lately.

Please keep us informed about this project when you do the flight testing.

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02-21-2014 04:35 AM  3 years agoPost 10
RM3

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Killeen, Texas - USA

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Your new clutch may end up slipping.
nope...wrong again.

here you go.

Watch at YouTube

still testing..and its still holding up very well.
if the springs ever wear out...just replace the springs...you don't even have to remove it from the fan hub...

It would be nice to see clutches of this design in 600 - 800 class nitros as well...granted they would cost more, but at least your not messing with the whole gap thing...

showing a preference will only get you into trouble, 90% of everything is crap...

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02-21-2014 10:44 AM  3 years agoPost 11
Four Stroker

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Atlanta

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Do you lubricate the pivot pins ? Where did the springs come from ? This is the kind of experimental hobby project that I like.

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02-21-2014 11:32 AM  3 years agoPost 12
1heliman

rrApprentice

us

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sixty thousands gap??? WOW. I can see ten at the most. But hey if it works for you that's good I guess.

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02-21-2014 01:07 PM  3 years agoPost 13
jschenck

rrProfessor

La Vista, NE.

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sixty thousands gap??? WOW. I can see ten at the most. But hey if it works for you that's good I guess.
It works because it's a different design. Need to be clear for everyone here this will NOT work for a one piece spring steel style clutch common in our kits. Our typical clutch should look for a .008" (.2mm) gap.

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02-21-2014 04:14 PM  3 years agoPost 14
AirWolfRC

rrProfessor

42½ N, 83½ W

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still testing..and its still holding up very well.
Your clutch engages at a reasonable speed so slipping would seem to not be a problem.

Where did you get the design to build from ?

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02-21-2014 07:50 PM  3 years agoPost 15
RM3

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Killeen, Texas - USA

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I was looking online for an alternative clutch for my radikal...I also tried looking for aftermarket clutches for 600 and 700 class nitros...but they were all the same design.

I wanted what the MA Whiplash G was using as it did not suffer from liner gap issues...but it needed to have support on both sides of the shoe pivot pin to avoid cracking from stress. Alot of the RC car guys were running clutches like these with three or even four shoes...but not one of them could be retrofitted for use in my helis...most were way out of my "just experimenting" price range at over $150...they also came with no matching bell, a seperate cost...

so made up my own based on my needs and experiences.

showing a preference will only get you into trouble, 90% of everything is crap...

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02-21-2014 08:33 PM  3 years agoPost 16
AirWolfRC

rrProfessor

42½ N, 83½ W

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It looks like like your "backward acting" shoes and 3 instead of 2 makes up for the lower swinging mass of the individual shoes answering my earlier concern.

Being on pivots you can have any amount of clearance you want without having to worry about breaking shoes.

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02-21-2014 09:12 PM  3 years agoPost 17
RM3

rrElite Veteran

Killeen, Texas - USA

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"Swinging mass"

the reason alot of cluches use such a large mass for the shoe is to help overcome the thick spring tension of the flex point...

the flex point basically has an additional function of transferring the engine torque onto the bell...if it were too thin it would break under use due to the torque load and vibration.
so the typical flex point on these clutches has to be rather thick...The mass of the shoe must now be large enough to over come that spring tension when spun at a certin RPM...

the smaller shoes work because they don't have to overcome a large spring tension and the torque is not transferred via the spring itself, but rather the pin and shoe only.

there are plently of other clutches out there with similar designs to mine for gas engines that even use aluminum and plastic shoes... and use light compression or torsion springs instead...

the real reason IMHO the flex type clutch is used on our helis is cause its cheap and easy to manufacture in numbers with the fewest operations.

showing a preference will only get you into trouble, 90% of everything is crap...

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02-21-2014 11:52 PM  3 years agoPost 18
AirWolfRC

rrProfessor

42½ N, 83½ W

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the real reason IMHO the flex type clutch is used on our helis is cause its cheap and easy to manufacture in numbers with the fewest operations.
Of course . . . and if you maintain tight clearances, it works fine.

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