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Author Topic: Engine crankshaft end play.  (Read 1184 times)

Offline Perry Rose

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Engine crankshaft end play.
« on: April 25, 2022, 09:02:08 AM »
How little end play should there be in the crankshaft? I'm working on an LA .40 I assembled from spare parts and I'm wondering about the amount of end play. I have ways to reduce it. What should I shoot for? I'm thinking minimal without binding.
I may be wrong but I doubt it.
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Online Dan McEntee

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Re: Engine crankshaft end play.
« Reply #1 on: April 25, 2022, 09:27:24 AM »
  Do you have the thin sheet metal washer behind the prop drive hub? With out that, there is quite a bit of end play. With it in place I'm guessing there is about .010" to .020" of play but I don't think it's critical. As little as .005" or so will still function correctly.
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Offline Perry Rose

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Re: Engine crankshaft end play.
« Reply #2 on: April 25, 2022, 09:29:53 AM »
What I'm thinking of is a different style washer.
I may be wrong but I doubt it.
I wouldn't take her to a dog fight even if she had a chance to win.
The worst part of growing old is remembering when you were young.

Offline Lauri Malila

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Re: Engine crankshaft end play.
« Reply #3 on: April 25, 2022, 09:51:52 AM »
Just make sure it's not too small as aluminium case will expand more than shaft when hot, and it may jam. Other than that, I don't think it's very critical. L
« Last Edit: April 25, 2022, 10:27:52 AM by Lauri Malila »

Online Dan McEntee

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Re: Engine crankshaft end play.
« Reply #4 on: April 25, 2022, 10:19:50 AM »
What I'm thinking of is a different style washer.

   I'm not understanding what that could be?? The standard washer that the FP's, and LA's have all used is a smooth, black hardened washer that us there just to help take abuse from electric starters I believe. I can dig one up and measure it if need be, but I think they are all the same. The casting for the case sometimes gets a little sloppy around the main bearing and if you think it is too tight with everything installed, you can lap that off a bit to create some clearance.
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Offline Brett Buck

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Re: Engine crankshaft end play.
« Reply #5 on: April 25, 2022, 10:28:02 AM »
How little end play should there be in the crankshaft? I'm working on an LA .40 I assembled from spare parts and I'm wondering about the amount of end play. I have ways to reduce it. What should I shoot for? I'm thinking minimal without binding.

   Unless it is hitting the backplate, I would be very tempted to leave it alone. Dan is right, there should be a hardened steel washer behind the thrust washer, and they are frequently lost. It probably doesn't need that washer if you are hand-starting it, and it's maybe .005-.008" thick, so even if you ran without it, it's only slightly sloppier.

   When you are running, of course, the crank is pulled forward by the thrust.

       Brett

Offline Perry Rose

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Re: Engine crankshaft end play.
« Reply #6 on: April 25, 2022, 11:50:37 AM »
All the original parts are in place. I was just wondering how it could be made better. I was thinking on a counter bored washer, kinda expensive, trimming the end of the crankshaft, again kinda expensive or a washer in front of the counter weight inside the engine which would be quite thin and subject to wear. Nothing ventured nothing gained.
I may be wrong but I doubt it.
I wouldn't take her to a dog fight even if she had a chance to win.
The worst part of growing old is remembering when you were young.

Offline Lauri Malila

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Re: Engine crankshaft end play.
« Reply #7 on: April 25, 2022, 12:28:25 PM »
I think the only way to improve the situation would be to get an engine with ball bearings. I would hesitate to put any extra washers inside the case, they can be counterproductive.
If I seriously had to improve the bottom end, I'd lap the shaft to mirror finish, diamond coat it and optimise the surface quality & geometry of bronze bushing by some honing. But with an engine like that, it's just not worth it. L

Offline Tim Wescott

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Re: Engine crankshaft end play.
« Reply #8 on: April 25, 2022, 05:38:36 PM »
In spite of hundreds, perhaps thousands of attempts at wearing out my most-used 46LA in normal Stunt wear, I have failed.

It has the usual LA "clunk-clunk" amount of end play (probably Dan's 10-20 thou).

So, to me that's a strong indication that things should be left well enough alone.  Put it in a plane, fly it, have fun.
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Offline Brett Buck

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Re: Engine crankshaft end play.
« Reply #9 on: April 25, 2022, 07:59:00 PM »
All the original parts are in place. I was just wondering how it could be made better. I was thinking on a counter bored washer, kinda expensive, trimming the end of the crankshaft, again kinda expensive or a washer in front of the counter weight inside the engine which would be quite thin and subject to wear. Nothing ventured nothing gained.

    Just put another thrust washer in where the normal one goes. But, beware of getting to too small as Lauri notes.

     Brett

Offline Motorman

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Re: Engine crankshaft end play.
« Reply #10 on: April 25, 2022, 09:25:45 PM »
Perry, I just measured 3 of my LA 46 engines. The new one with no run time has .005" axial end play, the one with a little run time has .006" and the one that's almost worn out has .007" end play. I've never used an electric starter on any of these engines.

Motorman 8)

Offline Lauri Malila

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Re: Engine crankshaft end play.
« Reply #11 on: April 25, 2022, 11:16:38 PM »
Btw, I'm sure you can buy those precision spring steel washers in various thicknesses, with at least 0,1mm increments. Check from the usual suspects like McMaster, for example.
Just for curiosity, what are the washer od & id, and what's the shaft diameter?
I'm sure the beforementioned DLC coating would be a very interesting improvement. When done right, it'll basically stop the wear and allow the use of much thinner oils. A real game changer. L

Offline Brett Buck

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Re: Engine crankshaft end play.
« Reply #12 on: April 26, 2022, 12:05:11 AM »
Perry, I just measured 3 of my LA 46 engines. The new one with no run time has .005" axial end play, the one with a little run time has .006" and the one that's almost worn out has .007" end play. I've never used an electric starter on any of these engines.

   All of which are perfectly OK.

      Brett

Offline Motorman

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Re: Engine crankshaft end play.
« Reply #13 on: April 26, 2022, 06:32:05 PM »
DLC coating would be a very interesting improvement.

Please tell us more about DLC coating. Where does one get that done? It seems a little beyond the home shop. Has it been used on piston/sleeve assemblies?

Motorman 8)

Offline Lauri Malila

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Re: Engine crankshaft end play.
« Reply #14 on: April 26, 2022, 10:57:35 PM »
Mm,

I wrote about my diamond coating experiments in another thread not too long ago, it's easily found with search. we can continue there.. L

Offline Dave Hull

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Re: Engine crankshaft end play.
« Reply #15 on: April 27, 2022, 02:46:12 PM »
The old OS .35 Max-S had about .012". And, as far as I know, no thrust washer.

Dave

Online Dan McEntee

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Re: Engine crankshaft end play.
« Reply #16 on: April 27, 2022, 07:32:24 PM »
The old OS .35 Max-S had about .012". And, as far as I know, no thrust washer.

Dave

   I'm not exactly sure, but I think they did. I would have to check my stash and see if I have a parts list. Most guys would lose them when the drive hub would fall off while changing props and such, the same as today. If the .35S didn't have one stock from the factory I think it would benefit form having one just to take some stress off the rod while in normal use.
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Offline Brett Buck

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Re: Engine crankshaft end play.
« Reply #17 on: April 27, 2022, 07:38:07 PM »
The old OS .35 Max-S had about .012". And, as far as I know, no thrust washer.

Dave

   I seem to recall that it had one, and as Dan notes, they are frequently lost.

   I really don't think it makes any difference - I have seen plain-bearing engines with on the order of 1/16" of end play run perfectly well.

    Brett

Offline Dave Hull

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Re: Engine crankshaft end play.
« Reply #18 on: April 28, 2022, 01:43:44 AM »
I checked a couple more of my OS Max-S engines. They all have a .005" steel washer. I just didn't get one in the engine I rescued last week...but it also had a Home Despot flat washer under the prop nut, too.

But,....neither the OS instruction sheet for the Max-S .30R/C nor the Max-S .35 Stunt lists a shaft spacer (friction washer, anti-wear washer, precision shaft spacer, etc.) in their respective parts lists. The .35 instruction sheet has an exploded view which does not show a washer either.

The fate of the world is obviously not hanging on this detail, but it was interesting to see if they came that way, or if there have been gnomes at work throughout the land, placing precision shaft spacers on all OS products not so endowed by the factory. And if so, are those skilled little guys available at reasonable rates to replace worn piston/liner setups....

Dave


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