Author Topic: Retlas  (Read 67959 times)

Online Chipmaster

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Re: Retlas
« Reply #345 on: November 26, 2018, 12:48:58 PM »
Hi Jo,
the half time gear is indeed mounted on an eccentric shaft as I described in the post. The whine is present with a tight engagement as well.

Andy

Offline Jasonb

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Re: Retlas
« Reply #346 on: November 26, 2018, 01:17:59 PM »
It almost sounds like the gears are under a lot more load that they should be. How easily does it free wheel with one of the valves held open so there is no compression as it does seem to loose speed quite quickly after a hit.

Online Chipmaster

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Re: Retlas
« Reply #347 on: November 26, 2018, 01:49:01 PM »
Hi Jason, Iíll check that later this afternoon and report back.
 I thought it was free when I assembled the timing gear, the timing gears have whined from the outset. It sounds the same in videos made last year before I took it apart for painting.
Andy

Offline Jasonb

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Re: Retlas
« Reply #348 on: November 26, 2018, 02:05:55 PM »
Another thing to check is that the gears are running concentrically, if the bore in one is a bit off maybe where the stock gear has been altered then it will be going in and out of mesh as it goes round and that can also give a whining. It's a bit hard to see if that is happening on the video due to the rods and eccentric but should be easy enough to check when turning over by hand.

Offline Alyn Foundry

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Re: Retlas
« Reply #349 on: November 26, 2018, 02:40:24 PM »
Hi Andy.

The Retlas is now running quite nicely as far as I'm concerned.

The gears, I wonder if HPC would have any ideas about the whining noise if you were to ask them?

As Jason points out the noise is like a " tight " drive or heavy loading upon them.

Cheers Graham.

Online Chipmaster

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Re: Retlas
« Reply #350 on: November 26, 2018, 06:29:59 PM »
Good evening Jason, Graham, Jo, et al.
Here's a link to a video of my timing gears that I've just uploaded on YouTube. I don't think they're subject to a load that would make them whine. The grey deposits are molybdenum disulphide stuff that I added to the lubrication thinking it would help - not ground up gear teeth.


RSVP

Andy

Offline Jasonb

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Re: Retlas
« Reply #351 on: November 26, 2018, 06:51:41 PM »
1 they look to have far too much backlash.

2. If you look at the gap between the guard and gear at about the 8 o'clock position you can see it starts off a lot more that at about 11 secs in which suggests the gear is not true.

Offline Alyn Foundry

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Re: Retlas
« Reply #352 on: November 26, 2018, 07:04:48 PM »
Hi Andy.

Here it is....

http://www.modelenginemaker.com/index.php/topic,5720.msg124050.html#msg124050

I built this one for a customer around 25 years ago, so long ago I can't remember what gears I used. They are about 1/4" to 5/16" wide, might have been from a JAP ( J A Prestwich ) engine.

Cheers Graham.

Offline RayW

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Re: Retlas
« Reply #353 on: November 26, 2018, 07:43:11 PM »
Could it mean that the large gear is bored slightly off-centre resulting in the meshing varying as it revolves?

Ray
Ray

Online Chipmaster

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Re: Retlas
« Reply #354 on: November 26, 2018, 07:44:08 PM »
Hi Jason, you're going forensic and I'm not following you or perhaps I'm just not seeing enough detail in those stills from the video. As the half time gear is on an eccentric shaft which is not concentric with the gear guard I would expect the clearance between the gear and guard to vary around the circumference of the static gear. However, are you  looking at a fixed point of the guard and seeing the clearance vary as the gear rotates? If so then yes that is evidence that the gear isn't true.. It will be annoying if the gear isn't true.

I'll take the gear off tomorrow and do some some measuring. 

Andy
« Last Edit: November 26, 2018, 09:07:17 PM by Chipmaster »

Offline Alyn Foundry

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Re: Retlas
« Reply #355 on: November 26, 2018, 07:44:32 PM »
I think Jason might have spotted the problem.

Do you have a set of " Soft " jaws for your lathe? I'd suggest creating a bore to suit the OD of the half time gear and then " clock " the hole. You could then bore and bush the gear to make it concentric again.

Cheers Graham.

Offline Jasonb

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Re: Retlas
« Reply #356 on: November 26, 2018, 07:51:19 PM »
The gear should rotate concentrically on a shaft that is eccentric to it's mounting hole, that way you can rotate the shaft which varies the mesh (backlash) of the gears.

I'll did out some drawings to show you what I mean.

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Re: Retlas
« Reply #357 on: November 26, 2018, 07:52:34 PM »
Ok
Thanks Jason, Graham and Ray.
I'll examine the gear tomorrow, it's too cold to work in my garage tonight.
I haven't got soft jaws for my lathe but I reckon I could sleeve the gear and set it up accurately in order to machine a true bore.

Andy

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Re: Retlas
« Reply #358 on: November 26, 2018, 08:00:46 PM »
Hi Jason, there has been a little flurry of posts crossing in the ethers over this.
I understand what your're saying about the half time gear should still be concentric with the shaft on which it rotates I intended rotation of the eccentric shaft to be the means of adjusting backlash at the outset.
Thanks for your continuing help.

Andy

Offline Jasonb

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Re: Retlas
« Reply #359 on: November 26, 2018, 08:03:34 PM »
Yes that's as it should be but those couple of screen shots show that the gap between gear cover and gear is not constant which suggests the gear is running out of true.

I just did this video anyway which is good for showing how the eccentric lets the gear mesh be adjusted, in this case completely taking the gear out of mesh to stop the drive to a pump jack.