Allchin compensating Centre

This topic has 16 replies, 7 voices, and was last updated 18 February 2022 at 17:11 by Dougie Swan.

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17 February 2022 at 17:39 #585928
Dougie Swan
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@dougieswan43463
Hi

I've just machined the centre on the allchin I'm building

It all go's together like it should but at some point it always binds

When I run each side separately against the three idler gears they run smooth as a nut, running them together is the issue

Anybody got any suggestions

Thanks

Dougie
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17 February 2022 at 17:39 #33976
Dougie Swan
Participant
@dougieswan43463
17 February 2022 at 19:01 #585942
MichaelR
Participant
@michaelr
Dougie, check the three pinion spacings they have to be spot on equal to run smoothly.

MichaelR
17 February 2022 at 19:05 #585943
noel shelley
Participant
@noelshelley55608
Sounds as though something is not inline ? Would a period of running in help to ease things or is it to bad for that ? This is a difficult assembly to make and requires precision to work well, I would check dimentions and alinement of all parts,may be easing a bit may help. Noel
17 February 2022 at 19:26 #585949
Clive Brown 1
Participant
@clivebrown1
If the mesh is too close, very small inaccuracies will cause tight spots. Try easing the large gears very slightly further apart, I found that a very slight easing of mesh made a big difference. There is a limit to how far this can be taken of course.

Hughes gives quite detailed advice on the machining, including a drilling jig.

Edited By Clive Brown 1 on 17/02/2022 19:29:06
17 February 2022 at 20:57 #585969
Paul Lousick
Participant
@paullousick59116
As stated, if the spacing of the planetary gears are not exactly the same, they will bind.

Paul
18 February 2022 at 13:01 #586066
Dougie Swan
Participant
@dougieswan43463
Hi and thanks for all the suggestions

I was thinking about the spacing but if it was incorrect then it would bind when I ran either of the side gears but individually they run sweet, only when I fit both sides do they bind

I will keep trying

Dougie
18 February 2022 at 13:30 #586080
Clive Brown 1
Participant
@clivebrown1
Running with only 1 large bevel is not really a very demanding test. The 3 smaller wheels can each take up their own mesh positions independently of each other.

As I see it, only when the 2nd. large bevel is also in mesh do all 5 bevel gears become interconnected and errors will cause binding.

Edited By Clive Brown 1 on 18/02/2022 13:36:22
18 February 2022 at 13:32 #586081
Anonymous
With both bevel gears fitted does the centre run smoothly at some points and bind at others? Or does it bind everywhere? If the former then I'd suspect an axial misalignment of the bevel gears rather than radial misalignment of the pinions.

Andrew
18 February 2022 at 13:44 #586083
Dougie Swan
Participant
@dougieswan43463
Hi

Yes, as Andrew said, the gears only bind at one point

Running both bevels against the pinions with one centre removed everything is fine

D
18 February 2022 at 14:18 #586090
Anonymous
I'm not familiar with the detail of the Allchin design, but it seems like one of the bevel gears is not concentric with it's axis. How were the bevel gears manufactured?

Andrew
18 February 2022 at 14:26 #586091
Dougie Swan
Participant
@dougieswan43463
The gears were bought from reeves

Dougie
18 February 2022 at 15:29 #586100
Anonymous
Some pictures of the parts would useful.

Andrew
18 February 2022 at 15:42 #586104
Dougie Swan
Participant
@dougieswan43463
Thanks to all who replied

I've got it sorted

I adjusted the position of the planetary gears out from the centre with a couple of shim washers under each gear

0. 26mm was what it took, I have been at this for a week and was starting to lose the will to live.

The combined knowledge of the members never ceases to amaze me

Thanks again

Dougie

P. S. Sorry for no pics but it's a pain having to load them to the album first then onto the thread

Edited By Dougie Swan on 18/02/2022 15:55:25
18 February 2022 at 15:59 #586109
Anonymous
Posted by Dougie Swan on 18/02/2022 15:42:23:

Sorry for no pics but it's a pain having to load them to the album first then onto the thread

Conversely it's a pain having to second guess about parts with which we're not familiar.

Glad it's been fixed, but I suspect the shmming has hidden the original problem rather than solved it. Is the backlash consistent or does it vary as the bevel gear is rotated?

Andrew
18 February 2022 at 16:55 #586116
JasonB
Moderator
@jasonb
The Fowler has a shim washer that sets the spacing between the two halves of the diff which is machined until you have minimal backlash but not too tight to bind, as it uses cast finish gears a little adjustment is needed on each engine.

For Andrew (and others) enlightenment extract from Allchin drawings
18 February 2022 at 17:11 #586119
Dougie Swan
Participant
@dougieswan43463
Thanks Jason

Dougie
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