Bevel + Mitre Gears

Whats the difference between the two?
I'm considering using bevel gears (mitre?) to drive the governor on a small stationary steam engine. The drive would be 2:1 from the crankshaft then 1:1 to drive the governor. The crankshaft is 7/16inch and the flywheel is 7-1/2 inch diameter. The governor driveshaft can be chosen to suit, probably 3/16.
Two challenges are to get the large gear on the crankshaft in proportion to the flywheel and to find a supplier who want less than £20 a piece + VAT +P&P which makes the thing not doable. RS don't have what I'm looking for and HPC looks like well into £100 for the four. EN8 or equivalent would be fine. Bronze gears would be great but I dread to think what the cost wouldbe.
Any suggestions?
Steve

If you could change the ratios around and have 2:1 at the governor then th egears that I bought for my traction engine governor will do, brass with 1/4" bor to the large wheel, 3/16" in the small but you could solder in a bush. All for about £20 the pair. If they suit I will post details.
Jason

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Why not make your own? Peter

wrote:
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Why not make your own? Peter
Looks too dificult - I have a mill and decent rotary table, so plain spur gears I can do, but bevel gears look beyond beyond me.

Steve wrote:
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Wise decision. Proper bevel gears cannot be milled as the tooth pitch is not constant.

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So machine them as parallel depth bevels, it was a dodge brought out in WWI so engineering shops could do bevels along a simpler line. It save the hand fitting needed to part of the addendum.
John S.

On Fri, 30 Jan 2009 15:18:48 -0800 (PST), John S
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Doesn't that involve a second cut with the gear advanced a bit to thin the teeth?
I'm sure Ivan Law had something to say on the subject.
regards Mark Rand RTFM

There are errors in Law's methods. Been a recent post about cutting bevels on this forum.
http://modeleng.proboards20.com/index.cgi?board=general&action=display&thread282
Another thought to keep the costs down as the gears don't need to transmit much load is to use an off the shelf gear with a smaller O/A dia and bore, then bore it out to suit the 7/16 shaft.
Jason

wrote:
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So machine them as parallel depth bevels, it was a dodge brought out in WWI so engineering shops could do bevels along a simpler line. It save the hand fitting needed to part of the addendum.
John S.
Is this the thing -
ME Vol 130, No.3261 p814 "Cutting bevel gears by the parallel depth method" by R.S.Minchin might offer some sensible advice.

wrote:
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So machine them as parallel depth bevels, it was a dodge brought out in WWI so engineering shops could do bevels along a simpler line. It save the hand fitting needed to part of the addendum.
John S.
Just found this as a legitimate PDF download - Handbook for machine designers, shop men and draftsmen (1916) which has trhe design data and method on p113 - 116

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You need a dividing head which can be tilted, you will find the calculations in Machinerys handbook. I have done several but it does take time and concentration, If you need help contact me. Peter

On Thu, 29 Jan 2009 22:17:24 -0000, "Steve"
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Don't know about prices, I've not used them for a while, but SH Muffett were helpful a few years ago. www.muffettgears.co.uk/
Richard