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My teeth do not mesh!

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Brian Dickinson27/11/2011 19:35:44
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Nearly 20 years ago I made a 3” Suffolk dredging tractor to the J Haining design. It took me about 9 months, doing bits at home and then going to a night school at Penistone Grammar school one night a week.

I was very pleased with the outcome which worked well.


Much to my dads disgust I sold it! The proceeds building me a double brick garage to replace the sectional concrete one I had. The new garage became my new workshop as well.


I then started a 4” Durham traction engine, which I got on to its wheels before I started a new job, the engine then never progressed as most of my time was spent in the US. Si I sold it – big mistake.


Now 16 or so years on, I am on my second 4” Durham, which is progressing nicely.


My question is – is anyone else making one and how does you bell gear mesh with the second shaft gear?? Mine with the gear tooth form scaled up looks terrible with a large gap between tooth top and root.


Has anyone made a 2” model and had the same problem?


I am thinking of replacing the horn plates for ones with a different centre distance between crank shaft and second shaft to make them mesh correctly to get over it. In doing this I do not think that anything will be too short on the piston rods or motion.



Brian

JasonB27/11/2011 19:41:16
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Brian how do you mean "the tooth form scaled up" its usual to half the DP when you double the size of an engine this should keep ratios and PCD's the same.
 
You will get a gap between tooth top & root but the edges of the teeth should mesh, something like this
 
J

Edited By JasonB on 27/11/2011 19:44:28

Edited By JasonB on 27/11/2011 19:45:18

Brian Dickinson27/11/2011 19:45:07
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Well i had them done at a local firm after i had given them the drawings. What they have done is correct but i wonder if there is a problem with he drawings that Mr Haining did.
 
I am not a club member or know anyone with one so i am kinda on my own.
 
Brian
Brian Dickinson27/11/2011 19:46:44
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They have a bigger gap than the picture that you have linked
JasonB27/11/2011 19:47:51
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This lists some errors but does not mention the gears
JasonB27/11/2011 19:49:24
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Whats the drawing spec for the 2" gears eg No of teeth, DP and gear ctr to ctr and what have the larger ones been cut to?
 
J
Brian Dickinson27/11/2011 19:51:08
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I will check it out tomoz and repost
Brian Dickinson27/11/2011 19:57:19
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HAHA it lists all the corrections that i have had to make to parts as i have gone along. i like the spectacle plate one, i made a really nice job of the plate and flange only find i had drilled it wrong. I corrected the horn plate and it looks ok but i aint sure if i changed the right part!!
 
I tried to put a photo in the reply but it did not work of a 2" on Station road steams page of one he sold and that has large gaps in the teeth so i think the drawings scaled up make the error look worse.
Stub Mandrel27/11/2011 20:58:22
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Brian,
 
if you post the PCD, DP, diameter and number of teeth I'll do the calcs for you and post the answers here according to my souces. You can then check them against JH's dimensions, whilst someone else finds the errors in my calcs.
 
Neil
Brian Dickinson30/11/2011 03:04:55
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I have tried to upload some photos of the gears but for some reason when i press the insert a photo button it comes up with a no entry sign?
 
How can i attached them?
 
B
JasonB30/11/2011 07:20:56
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Add them to the ones that are already in your album, but if thats what you tried first then make sure they are .jpg format.
 
Failing that I've sent you a PM
 
J
MichaelR30/11/2011 09:40:39
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I built a Durham & NY many years ago, the gears set as drawing do have,( for want of a better word) " loose mesh".
 
I have a picture in my album, it's not very good but may help. bearing in mind all the muck and oil that gathers on the gears you don't want them meshing too close.
 
Stick
 
 

Edited By Stick on 30/11/2011 09:41:13

mgj30/11/2011 12:47:11
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Remember too that the originals were built by blacksmiths, and many of the gears were cast, and worn. Precision involute gears they probably were not.
 
So as long as the sides of the teeth engage, they will transmit drive, and you will get that nice clang clang of a real traction engine out of it.(and probably for the same reasons too!
 
If there is a problem, and they actually miss or skip, can you machine up a couple of eccentrics (one eccentric and part off of course) and pop them in the housings and adjust out some or all of the slack that way.
Stub Mandrel30/11/2011 18:27:22
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Take a close look at the gear profile in this picture.
 
Lots of cast gears on the canal.
 
Neil
 
JasonB30/11/2011 20:22:35
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Yes the traction engine gear teeth were a longer profile, this also helped on the ones with sprung rear ends as it allowed some movement without the teeth comming out of mesh, though Fowlers had their version of an oldham coupling to take up the movement.
 
J
mgj30/11/2011 22:33:46
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Brilliant- fit where they touch. Bet they clank a bit too.
Brian Dickinson01/12/2011 05:57:42
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I have added photos of the gears to my album.
Stub Mandrel01/12/2011 21:29:49
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Hi Brian,
 
I'm not convinced that gap is too large for what would probably have been cast gears. If you look at the 'wear notch' on that canal crane gear you can see its pinion would have meshed more loosely than your do. Also note the very long thin teeth, even allowing for wear.
 
Neil
mgj01/12/2011 23:19:53
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Well you have several choices.
 
1 Remake the hotrnplates and get a tight mesh. Personally I wouldn't bother with that.
2. Do the calculations and see if you can fit one more tooth in on one of the gears. Wouldn't bother with that either at this stage.
3. Redo the calculations and fit a close but different ratio using 2 different gears. Problem with that is that small changes in ratio actually make quite a difference in running.
4. Try the eccentric bushes route , if its a real problem.
5. Finish the engine and see if its a problem. If it isn't, which is the most likely outcome, forget about hte problem. If it is, wel lyou still have (1,)2,3,4 above to try.
 
Like Stub Mandrel suggests, a dose of forgetfulness might be best. They'll be a bit noisy, thats all, but then straight cut gears always are, so thats hardly dramatic. Not going to break, and will transmit drive.
Ian S C02/12/2011 07:56:38
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A wee bit OT,
These are the gears on the vintage turbine at our museum, the one on the vertical shaft consists of a cast iron frame, with wooden teeth. I suspect that the teeth are mostly origional, meaning that they date back to about 1880. The gears are about 3ft dia, and transfering about 8 hp at about 120/150 rpm. Ian S C Theres another photo in the album under Homebush NZ

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