Author Topic: Lane and Bodley 400hp Corliss  (Read 41193 times)

Offline Captain Jerry

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Re: Lane and Bodley 400hp Corliss
« Reply #300 on: July 15, 2019, 04:03:22 AM »
Hello Simon,


I have been following this build quietly since there is not much that I could add other than "Wow." This will be a grand model when finished. I have been particularly interested in the valve release mechanism and can barely wait to see it in operation. Of the many MEM Corliss models built, I don't believe that any have been able to implement the release and although there were problems implementing the Crab Claw, the somewhat more easily made Reynolds release is nearly impossible to build such that it will work reliably. Heaven knows,I have tried. Scale is the problem as I am sure you know. I believe that the MEM version is just too small. The distance between the steam valve bores is less than two inches. It would be useful to know a bit more about the size of your model.  Distance between valve bores or just what the piston stroke is would help put it in perspective.  I am beginning to think that 2.5" to 3" stroke is a minimum for a working release.


Jerry
There are thing that you can do and some things you can't do.
Don't worry about it. try it anyway.

Offline sco

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Re: Lane and Bodley 400hp Corliss
« Reply #301 on: July 15, 2019, 07:44:55 AM »
Thanks Pavel.

Jerry,

After being mesmerised by the Corliss valve gear on one of the engines at the Forncett Steam Museum I felt compelled to try and build a model with a proper trip release.  The Lane and Bodley was one of only a very few casting set Corliss models available on the market and although not the same trip mechanism as the engine in the museum I really like the look of the crab claw.  I'm hopeful that not only will the mechanism have a satisfying 'click' on release but will also work to properly control the speed of the engine.

Simon.
Ars longa, vita brevis.

Offline Dennis

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Re: Lane and Bodley 400hp Corliss
« Reply #302 on: July 20, 2019, 08:01:22 PM »
Simon,
Thanks for the information on the flywheel keys.  I think you have a good approach for a model that will run without load.  As Kurt said, broaching all the way through that hub is difficult.  I was not able to get a full depth cut completely through the hub with my broach so had to turn the wheel over and press the broach from the other side to finish the cut.  It was not the easiest keyway I have ever broached.
Dennis

Offline Jasonb

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Re: Lane and Bodley 400hp Corliss
« Reply #303 on: July 20, 2019, 08:14:52 PM »
If you can't push your broach in far enough then you need an extension bar, or just make one from key steel

https://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Keyway-Broaches

https://www.arceurotrade.co.uk/projects/broaching/Internal-Keyways-and-Broaching.pdf

I've done 50mm long hubs with standard length broaches though it is best to make a bush the full length of the hub so the cutter does not get pushed off the surface.

Offline Dennis

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Re: Lane and Bodley 400hp Corliss
« Reply #304 on: July 23, 2019, 09:12:22 PM »
Thank you for the references Jason, I will check them out today.
Dennis

Offline sco

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Re: Lane and Bodley 400hp Corliss
« Reply #305 on: August 09, 2019, 09:20:12 PM »
Last few weeks I've been pondering the governor bevel gears, wanted to make them so ordered some mod0.5 cutters from China which took a few weeks to arrive.  I started by making the blanks and then the boring process of cutting the teeth - 20 teeth on the pinion (3 cuts per tooth), 72 teeth on the wheel (2 cuts per tooth). 

All done without mishap and they look ok but positioning them by hand they don't seem to mesh as well as I'd hoped so maybe I didn't cut the teeth deep enough.  I wanted a more square edged, flat faced tooth but the cutters obviously form involute shaped teeth - couldn't think of a way to get these so hopefully they will mesh ok once aligned properly.

Simon.
Ars longa, vita brevis.

Offline paul gough

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Re: Lane and Bodley 400hp Corliss
« Reply #306 on: August 10, 2019, 02:59:18 AM »
Hi Simon, Still sitting in the dark watching your work. Interested to know your thinking regarding the tooth profile on the govenor gears and your apparent preference for non-involute for this application??? Were you wanting something more cycloidal, 'clockish'? Regards Paul Gough.

Offline Elam Works

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Re: Lane and Bodley 400hp Corliss
« Reply #307 on: August 10, 2019, 04:00:16 AM »
Simon,

Using a 'fixed form' cutter to machine bevel gears is always going to be an approximation. There are various techniques for parallel depth miter gears and offsetting the cutter to take two passes to better transition from a large tooth at the outer rim to a small tooth at the inner edge, but none of them generate the true diminishing tooth that vanishes to a singularity at the cone vertex. So long as the face width is not too great, they can make a tooth that is 'good enough'. But it will feel 'lumpy' compared to commercially generated bevel gears. Sometimes easing off the teeth at the small end can help improve the mesh. A spot of Prussian Blue might highlight where it is binding.

-Doug

Offline Jasonb

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Re: Lane and Bodley 400hp Corliss
« Reply #308 on: August 10, 2019, 07:16:38 AM »
Simon, did you remember to use a cutter for a larger tooth count than the number on your bevel gears as that would mean a cutter that will produce straighter sides teeth as it gets more towards a rack. I'm assuming your 3 cuts were at different settings not just 3 passes to get to depth.

Also I expect your MOD cutters are 20pa, had you use 14.5pa typically found on DP cutters than you would also have got a slightly flatter tooth flank

I'd put one on a spindle so it is free to turn and mount the other on an arbor and run the two together with some 600 or 1000g powder and oul.

Offline sco

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Re: Lane and Bodley 400hp Corliss
« Reply #309 on: August 10, 2019, 11:44:31 AM »
Thanks for all the replies, below are some pictures of the real gears showing the tooth form.

Jason; yes I did use a cutter with a larger tooth count for the pinion (28T for 20T), the three cuts for the pinion were a roughing cut on centre and then two cuts with the gear rotated +/- 1/4 tooth and the cutter +/- offset vertically, for the wheel I just did the two offset cuts as didn't have a suitable dividing plate for 1/4 a tooth only 1/2 a tooth.  Searched initially for 48DP cutters but couldn't find a full set so went for mod0.5 instead.

Not sure there is actually a problem with them yet - going to try and position them with some Vee blocks and see if they feel any better.

I used a spreadsheet to size the gears that Don provided for a standard 45degree cone angle, the sheet also includes some notes by Gail for how to lay out the gears from scratch - if I follow that method then I get very different angles for the pinion and wheel, something like 15degrees for the pinion and 75degrees for the wheel - not sure if that would have given me a better looking result?

Simon.
Ars longa, vita brevis.

Offline Jasonb

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Re: Lane and Bodley 400hp Corliss
« Reply #310 on: August 10, 2019, 12:39:40 PM »
I've only ever cut uneven numbered pairs at the calculated angle where the two angles add up to 90deg. For equal numbers of teeth I cut both at 45deg so that may be part of the issue. So would have cut at 15.48 and 74.52 deg

Offline sco

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Re: Lane and Bodley 400hp Corliss
« Reply #311 on: August 10, 2019, 12:47:32 PM »
Is there some rule then for how the angle should be split as that angle ratio isn't the same as the tooth count ratio?
Ars longa, vita brevis.

Offline Jasonb

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Re: Lane and Bodley 400hp Corliss
« Reply #312 on: August 10, 2019, 01:19:25 PM »
« Last Edit: August 10, 2019, 01:27:02 PM by Jasonb »

Offline sco

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Re: Lane and Bodley 400hp Corliss
« Reply #313 on: August 11, 2019, 10:43:11 AM »
I've re-cut the teeth with the new cone angles as advised by Jason and they now mesh more convincingly  ;D

Simon.
Ars longa, vita brevis.

Offline Jasonb

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Re: Lane and Bodley 400hp Corliss
« Reply #314 on: August 11, 2019, 01:17:51 PM »
And they look the part too :)