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Need to whip up a 3:1 open gear reverser

C

CalG

Diamond
Joined
Dec 30, 2008
Location
Vt USA
About 15 hp at less than 1000 rpm.

I'm thinking 5 or 6 DP. 12:36 reduction ratio. both on 1 inch shafts. pillow block mounting.

Is there any advantage to 14.5 over 20 degree PA?

Again, these gears will be open but covered.

It's a custom tractor snow blower application,
 
...Ahh yes, "Snow Lubricated".

Contrary to what many think about snow (and the sublimation thereof),
Cat publishes data on track wear, and Snow is pretty darn abrasive.

Anywhoo, it's elementary (should have learned it your machinist night school
training in power xmisssion class) the 20 (and 25 degree) have stronger
tooth forms, driving the vector of the forces into the teeth more, less bending.

But this sends more forces to the bearings.
 
digger doug said:
...Ahh yes, "Snow Lubricated".

Contrary to what many think about snow (and the sublimation thereof),
Cat publishes data on track wear, and Snow is pretty darn abrasive.

Anywhoo, it's elementary (should have learned it your machinist night school
training in power xmisssion class) the 20 (and 25 degree) have stronger
tooth forms, driving the vector of the forces into the teeth more, less bending.

But this sends more forces to the bearings.
Click to expand...

I'm not worried about strength, I'm worried about the abrasive snow and any mice that might get caught up in the works. Well, not the mice themselves, but the trouble they might cause to the gears.
 
You do use the term REVERSER, so you have to think of a third shaft with a reverse idler

The problem will be to have the right number of teeth on fixed center shafts so in one direction TWO gears happily work together while in the opposite direction THREE gears have to happily work with each other

Have fun
 
If your going to be grinding up mouse entrails.....ewh

I would think the 20 or 25 degree having the stronger tooth form would
help in this application (odd as it is mind you)

Go to that free gear layout site (gearmania or something) and punch in the numbers
and look at what the teeth look like.

Play around adjusting the PA, the centers, the number of teef, etc.
 
You want an 11:36 or 13:36 so you have a hunting tooth engagement. Is 15 hp the full output of the engine?
 
johnoder said:
You do use the term REVERSER, so you have to think of a third shaft with a reverse idler

The problem will be to have the right number of teeth on fixed center shafts so in one direction TWO gears happily work together while in the opposite direction THREE gears have to happily work with each other

Have fun
Click to expand...

John

A "reverser" is the direct nature of a two gear system. No third shaft, no idlers.
It really shouldn't be more difficult than change gears on a feed box. Except for the debris issues.
 
gbent said:
You want an 11:36 or 13:36 so you have a hunting tooth engagement. Is 15 hp the full output of the engine?
Click to expand...

18 hp oil burner, then through the gear box, power delivery limited by a plethora of shear pins. No worries, The present drive is via 420 chain
 
gbent said:
You want an 11:36 or 13:36 so you have a hunting tooth engagement. Is 15 hp the full output of the engine?
Click to expand...

Why would I care about a "hunting tooth"? This is an open gear box for a freakin TRACTOR!

Don't make things weird, Wear here and there will result in enough slop that "tooth to tooth" wear patterns will be insignificant.

If I could fit DPs less than 5, I would. But there are space constraints, and the shaft size is fixed at one inch.

Are there benefits to running 14.5 degree contact angle gears in "open gear" situations? That is the question. Boston Gear's very useful on line literature did not address that detail. Perhaps you have some experience to offer.
 
CalG said:
Are there benefits to running 14.5 degree contact angle gears in "open gear" situations? That is the question. Boston Gear's very useful on line literature did not address that detail. Perhaps you have some experience to offer.
Click to expand...
14.5* is a little quieter and backlash changes a little less with center distance changes. 20* is a little stronger. If you are buying change gears for an old lathe or something, 14.5 is more common because it is older and been around longer.

Generally, 20* is better for most stuff. If I were making your gears I'd go with 20*.

There's not really a huge difference between them if you can get 14.5* easier out of a catalog though.

About hunting tooth, not really necessary but if you can add a tooth to one side or the other so the ratio doesn't come out hitting the same place every revolution, it wouldn't hurt. If the load is like a power unmentionable but starts with "h", where the load is always in the same place every revolution and not even around the whole circumference, then it's worth doing.
 
EmanuelGoldstein said:
14.5* is a little quieter and backlash changes a little less with center distance changes. 20* is a little stronger. If you are buying change gears for an old lathe or something, 14.5 is more common because it is older and been around longer.

Generally, 20* is better for most stuff. If I were making your gears I'd go with 20*.

There's not really a huge difference between them if you can get 14.5* easier out of a catalog though.

About hunting tooth, not really necessary but if you can add a tooth to one side or the other so the ratio doesn't come out hitting the same place every revolution, it wouldn't hurt. If the load is like a power unmentionable but starts with "h", where the load is always in the same place every revolution and not even around the whole circumference, then it's worth doing.
Click to expand...

As to tooth count

I'll be at the mercy of the "in Stock" offerings. the 3:1 is nothing magic. But getting two gears in the space less than 7 inches wide limits the option,

This project does not have an unlimited budget!
 
CalG said:
As to tooth count

I'll be at the mercy of the "in Stock" offerings. the 3:1 is nothing magic. But getting two gears in the space less than 7 inches wide limits the option,

This project does not have an unlimited budget!
Click to expand...

Damned shame the space and layout do not permit robbing a junker of 3.18:1 third-member, housing, bearings and all.

WTF else might be cannibalizable, or MASS market parts-bin. though?

Shame to make gears or even pay full stock price in a world full of salvage with years of life left in it.

2:1 f'rinstance, timing gears come to mind. All-metal (one Aluminium, one hardend steel) for GMC were are only about fifty bucks the pair, brand-new.
 
CalG said:
I'll be at the mercy of the "in Stock" offerings. the 3:1 is nothing magic. But getting two gears in the space less than 7 inches wide limits the option,
Click to expand...
If you go 10 DP then if they have 17 for the pinion you could go 50 for the gear. That'd be darn close to 3:1 with the hunting advantage. If you go 10 DP I'd want to go 20* PA for sure.

Should have 17T in the catalog ? Usually in the smaller numbers they increment by one. I'd like to see you go 8 DP but hate to go anywhere near 14 teeth on the pinion. Undercut makes them weak as a kitten. I think the Browning and Boston stock gears are both long-addendum in that size but still. Tiny pinions suck.

If you can get a steel pinion and carburize it, run against a cast iron gear, spray on that nasty black open chain lube stuff every day, that oughter do ya for a while. It's only a tractor :D
 
20 is stronger and louder than 14.5
Otherwise it makes little difference.
20 is the "standard" these days.

Below 15? teeth 20 has undercut.

I would select my pitch so the pinion is above 15...
As mentioned, 17:50 is damn close, and avoids hunting and undercutting the pinion...if you can make that fit.
 
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