# Bevel Gears - Straight vs Skew



## Dwight Ennis (Jan 2, 2008)

I've been looking at Kozo's books on the Heisler and the Climax, and I have several questions about the gears.

The Heisler transmits power from the cylinders via a crankshaft to the central driveline, and from the driveline to the far axle on each truck via _straight tooth_ bevel gears.

The Climax transmits power from the cylinders to a shaft, and from the shaft to the central driveline via a set of _skew_ bevel gears.  The central driveline then transmits power to each axle via another set of _skew_ bevel gears.

1 - What is the advantage of _skew_ bevel gears over _straight_ bevel gears?  Is it stress reduction on individual gear teeth?

2 - What is the difference between skew gears and _helical_ (spiral) gears (other than the obvious straight vs spiral tooth configuration)?  In other words, I understand the difference in their form, but not in their application.

3 - On a small scale live steamer, would straight tooth bevel gears work just as well on the Climax as the skew bevel gears shown?

Any gear experts out there who can explain in layman's terms?


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## Eric M. (Jan 3, 2008)

Oh man Dwight, I don't have the answers but I'll bet you a can of butane that Henner is going to chime in on this one!

That is, unless someone else beats him to the correct answer.

Wait for it.....


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## David BaileyK27 (Jan 2, 2008)

Dwight, on the heisler the drive is on the centre line of the axle and only drives one set of wheels on each truck, the other wheels being driven by the Coulping Rods, on the Climax the drive shaft is above the centre line of the axles and drives both axles with a set of offset helical gears on each axle.
Daviod Bailey  www.djbengineering.co.uk


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## HMeinhold (Jan 2, 2008)

Dwight
As David Bailey pointed out, the skew bevel gears allow shafts to cross each other. Somewhere around 1990 gear cutters became availbale which could cut helical gears. These quickly replaced skew bevel gears because they could carry more load and were less noisy. So from a functional point of view skew bevel gears and helical gears are identical. Unfortunately for us, they don't look prototypical for a Climax (though they would work). So if you think of building a Climax, you have to roll up your sleeves, study Kozo's book and make your own. If I would not constantly chicken out on this task, I would have started my ride-on A-Climax...
Regards


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## Eric M. (Jan 3, 2008)

Ha! I knew Henner couldn't avoid this topic!  Who's your daddy!!/DesktopModules/NTForums/themes/mls/emoticons/hehe.gif  I'll be collecting my can of butane now, thank you very much!

Oh and BTW Dwight, perhaps you and Henner should look into having a CNC machine shop make you guys some gears for 1" scale Climaxes.  If you split the costs it might not be so bad.  Dwight I assume you would build a "B" Climax per Kozo's book and Henner would build an "A" Climax so you would both still have unique macines.  Just a thought.

Regards,


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## Dwight Ennis (Jan 2, 2008)

I can always count on this forum for answers to my own ignorance. hehehe I can see now what you're talking about after your explanations. Thank you! 

Eric - I might be able to cut them myself on my own CNC mill. Other than making the tooth cutting tool, it may well be do-able with what I already have, especially if I made them out of brass. 

I'd have to invest in the CNC rotary table. Well, I probably wouldn't HAVE to, but that would be cool to have anyway.  It would certainly be quite a project. 

There's a photo in Kozo's Heisler book of a 3/4" scale a guy built, but with 4-3/4" gauged trucks.  It looks proportional.  Something to also think about as far as scale goes.


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## Kovacjr (Jan 2, 2008)

You can save ALOT of cash and use the gears from fishing reels. They are skew bevel gears....Some are brass but some are a cheap casting on the low priced reels....But for the 3/4" or larger scales Boston Gear and a few others have stock gears that can be used. There is only 2 or 3 machines left in the world that still cut Sprial bevel gears in production. This is according to one of the gear companys I had contacted a while ago about replacement gears for my Aster Climax to run slower. I think Richmond Gear was one of them that still uses the machines.


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## HMeinhold (Jan 2, 2008)

Posted By Dwight Ennis on 03/27/2008 12:19 PM
I can always count on this forum for answers to my own ignorance. hehehe I can see now what you're talking about after your explanations. Thank you! 

Eric - I might be able to cut them myself on my own CNC mill. Other than making the tooth cutting tool, it may well be do-able with what I already have, especially if I made them out of brass. 

I'd have to invest in the CNC rotary table. Well, I probably wouldn't HAVE to, but that would be cool to have anyway.  It would certainly be quite a project. 

There's a photo in Kozo's Heisler book of a 3/4" scale a guy built, but with 4-3/4" gauged trucks.  It looks proportional.  Something to also think about as far as scale goes.

Dwight,
I volunteer to make the tooth cutting tool. In fact, I already bought the stock. But as I mentioned earlier, I am still chickening out...
Regards


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## Dwight Ennis (Jan 2, 2008)

I volunteer to make the tooth cutting tool.
Hmmmm... $395 for the CNC Rotary Table... maybe we can give this a whirl.  If worse comes to worse, I end up with a neat attachment anyway, and we waste a little brass and tool stock.


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## Ed Hume (Jan 3, 2008)

Dwight,

I machined brass skew bevel gears under full CNC control on the Sherline for my Gauge 1 Climax using Kozo's information.
See http://www.flickr.com/photos/edhume3/sets/72157600964223180/

In addition to the formed cutters, you will need to make a long reach saw cutter to reach the center of your rotary table.










I









However, the Sherline lacked rigidity to cut 303 stainless steel gears.  I moved the rotary table and control system to a full sized mill to cut SS gears.  

The Climax set on flickr has more photos.

Regards,
Ed


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