Author Topic: Changing the gearing on air powered tractor  (Read 649 times)

Offline galland

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Changing the gearing on air powered tractor
« on: July 17, 2017, 01:28:29 AM »
Probably a year ago or longer I posted 3 photos of a little air powered tractor that I somewhat modeled off the Mamod traction engine. I put gears on it and have never been happy with how they look. I had a 12 tooth driving a 69 tooth and then another 12-69. It got the job done and it ran well but looked some what strange with that big 69 sticking up in the air. As you see the 69 is almost as large as the rear wheels. Well I recently tore it down and have been studying how to change it to be a little more to scale. With smaller gears I am adding two more intermediate gears on the layout although one is just to keep it running forward rather than in reverse. Its well on its way and I will post finished photos shortly.     Gary

Online b.lindsey

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Re: Changing the gearing on air powered tractor
« Reply #1 on: July 17, 2017, 02:03:32 AM »
Hi Gary. I nay gave missed the original photos, but what a nice job you did on the little traction engine. I agree though, it will look more to scale with the new gear arrangement. Looking forward to seeing the final result.

Bill

Online Hugh Currin

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Re: Changing the gearing on air powered tractor
« Reply #2 on: July 17, 2017, 05:15:34 AM »
That is a cute and shiny tractor. Nice work.

Might be more work, design and construction, but have you thought about using an epicyclic (orbital) gear train? It's still a lot of gears and carriers, but it may fit into the design nicely. I start thinking this direction when there are more than 3 gear sets in a reduction. Just a thought.

Looking forward to seeing the results either way. Thanks.

Hugh

Offline galland

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Re: Changing the gearing on air powered tractor
« Reply #3 on: July 17, 2017, 02:47:49 PM »
Thanks guys. Hugh, I guess I never gave that type of gear train any thought when doing this. I have decided on the following photo for the way to go. It still is probably far from scale but I think its close enough for a toy tractor. It is quite small. The drive wheels are  1  5/8 inches tall and the main body which gets all the gears is 1.60 tall by 1.25 front to rear. I am using 48 pitch gears and they should have been 64's or smaller but its what I had. First off I found that I could not replace the first 69 tooth with a 36 because I didn't have the room to get that shaft in the top of the main body. I found that I could mill off .062 from the bottom of the engine block with out disturbing any other crucial dimensions so I did. The arrangement in the photo is.........The 12 on the engine drives #1 which is 36 with 12 in the center which drives #2 which is 36 and is mainly there to keep the drive wheels rotating properly. #2 drives #3 which is 36 with 12 driving #4 which is 48 teeth. I hope that made sense. As I said before I will post finished photos.     Gary

Online Hugh Currin

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Re: Changing the gearing on air powered tractor
« Reply #4 on: July 17, 2017, 04:07:34 PM »
Gary:

That should work well. Thanks.

Hugh

Offline galland

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Re: Changing the gearing on air powered tractor
« Reply #5 on: July 17, 2017, 09:01:36 PM »
Well the new gears are on and seem to turn really nice. Now that I look at it they still seem to big but are an improvement from the big 69 teeth. The new gear ratio is 36 turns of the engine for 1 at the drive wheel. After raising the first gear on the main body and lowering the engine the flywheel was to big to clear things so I made a new one. The final picture is all back together minus the cylinder. It sits on the uprights so it can be demonstrated with out going anywhere. Thanks for the interest.     Gary

Offline Ye-Ole Steam Dude

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Re: Changing the gearing on air powered tractor
« Reply #6 on: July 17, 2017, 11:02:56 PM »
Gary it looks real good,

You have done a super job on this build.

Online b.lindsey

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Re: Changing the gearing on air powered tractor
« Reply #7 on: July 18, 2017, 12:25:28 AM »
Ditto....the new gear train does look better!!

Bill

Offline Mark.j

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Re: Changing the gearing on air powered tractor
« Reply #8 on: July 30, 2017, 05:57:27 PM »
Really like this little tractor! The new gears look good!