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A poor man's right angle drive?

A poor man's right angle drive?

A poor man's right angle drive?


I have an agricultural application that requires the output from a small (50 hp) tractor engine to be delivered at a (horizontal) right angle to the engine drive shaft and then, through sprockets, to the chain driven machine. No gear reduction is required. Something suitable for a driveshaft input speed from 1000 RPM to 4000RPM continious duty is required.

Is there any reason I shouldn't try a regular automobile rear end differential? I would fix one output shaft stationary thus requiring all the all the power to be delivered to the other shaft. Most auto differentials have a 1:2 to 1:4 gear reduction but I can step it back up by selecting an appropriate size chain sprocket. What are the pitfalls in this scheme? Other than immobilizing and securing the one output shaft, what other modifications should I make? Your thoughts would be appreciated.

If this plan proves un-workable a PTO right angle gear box will have to be used. Here is a link to an outfit in Austrialia:  http://www.bareco.com.au/files/pto2002/selgearbox.htm . I've searched high and low on the Internet for a USA distributor/manufacture of this kind of gearbox with no joy. Can anyone supply a link?

Best Regards


RE: A poor man's right angle drive?

You will be putting a lot of load on the spider gears unless you lock the differential.

RE: A poor man's right angle drive?

Thanks Ross;

How does one "lock a differential"?

I thought I would have been doing that by immobilizing one of the output shafts. I must have been wrong though.

Best Regards,


RE: A poor man's right angle drive?

to lock it you could
 A  buy a spool or mini spool and install it
 B  do some welding of spider or side gears
 C  pour the spiders full of lead or aluminum

  locking 1 axle on an open differential will cause the spiders to behave like planetary gears increasing wear but also cutting the reduction in half ( 4 to 1 becomes 2 to 1 )  if its well lubed and lightly loaded that could work for you.
 good luck

RE: A poor man's right angle drive?

Differentials' spider gears and side gears can carry a lot of torque, but they don't have bearings that are suitable for continuous use.  Actually, they typically don't have bearings at all; they just run directly in the diff case.  They will overheat and seize in minutes, probably even at zero power level.

Mike Halloran
Pembroke Pines, FL, USA

RE: A poor man's right angle drive?

Kaptain,  if you do a search on "differential spools" or look at the Richmond Gear website, this is a common piece for drag racing cars.  But they are generally available only for larger differentials like the Ford 9" or GM 12-bolt.  They are dirt cheap for these units but not available for smaller ones.  Still, if you see the concept used on these commercially available ones, you should be able to have a machine shop knock out one for you pretty economically.

RE: A poor man's right angle drive?


Thanks for the tips and explainations.

This weekend I'm heading for a salvage yard in search of a cheap auto differential that I can take apart to see whats what inside. With an illustration in hand I guess I can figure out what is a "spider gear" and what is a "side gear". I'll see what happens when I "freeze" up a particular gear as if it were welded per FoMoCoMoFo's suggestion.

As I understand it, a "frozen" differential will result in a right angle drive with two output shafts both going in the same direction at the same speed. (i.e.: both "top going" or both "top coming" when viewed from drive shaft.)

My guess is that a differential from a independant rear suspension car would be more compact and be best for this purpose.

Thanks again for your advise.

Best Regards,


RE: A poor man's right angle drive?

I'm for FoMoCoMoFo's second option in your case. Buy a cheap diff and weld the sometimes called sun and planetary gears or the sometimes called side and spider gears together.

Strategic placing of pieces of the shaft of an old bolt can greatly increase the strength of the welding.


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RE: A poor man's right angle drive?

Interesting looking at that "howstuff works site" but can you see the deliberate mistake - Concave driving concave

RE: A poor man's right angle drive?

Commonly known as a CIG locker!


Was told it couldnt be done, so
i went and did it!

RE: A poor man's right angle drive?

Perhaps an industrial right angle drive can do the job. I've seen large ones go for cheap on ebay. I've only ever seen spiral bevels in them so they should run close to as smooth as a hypoid set.

RE: A poor man's right angle drive?

Quite a few new agri-applications have gone to hydraulic drive: pump & motor.  So you have drive by hose.

I myself have converted a large mid-mount finish mower to a frontend loader offset mounted unit using hydraulic power. Its a 50 HP application. You can ratio the displacements to get the rpm of the attachment you need; no chains, sprockets or extra shafts. And, you get the flexibility of mounting location and angulation.

Yes you'll need a reservoir, relief valve, pump, motor, hose and some connectors.  Maybe the tractor hydraulic supply can be utilized.  You end-users will appreciate the much simpler mchanism.  Mowers, hole diggers, rakes, combine heads and many other systems have given up the mechanical driveline (some needing constant velocity joints) in favor of fluid power delivery.  

RE: A poor man's right angle drive?

I like your "poor man's" approach of using an inexpensive automotive rearend. Should work just fine.

RE: A poor man's right angle drive?

My dad had a forage box made by a small local manufacturer in the late 60's. My dad actually worked for the guy one summer. He wouldn't by anything he could make, which included 90° gear boxes. Our forage box had a Ford 9" with one side cut off. ISZ

RE: A poor man's right angle drive?


You didn't say, but if you're being paid to design and build this device, why don't you do the professional thing and design a proper gearset to do the job right.  Will your customer be satisfied with cobbled-together junkyard parts?

If instead, this is just a garage project, for your own use, buy a new aftermarket, heavy duty, hypoid R&P set, and machine your own (steel) housing to fit your equipment.  

Be careful to provide adequate bearing support for the chain sprockets.  Especially if they're cantilevered.

RE: A poor man's right angle drive?


It's for my Father-in-law. I have access to a welder, drill press and metal cutting band saw. I don't have access to a lathe, milling machine or gear hobber. Therefore, I'm putting this thing together (as much as possible) with off the shelf components including pillow blocks, sprockets, power transmission chain, ground round stock, CV joints, adapters and sleeves. Most of these items are readly available at industrial/agricultural supply houses. And, being stock items, are quickly and inexpensively replaced when they wear out.

Chain drive and CV joints are very tolerant of the inevitabile lack of precision and general mis-alignment. Shims will take of the rest. I'm not designing a Ferrari, here.

Thanks for your reminder about "bearing support". I'll be sure to include a pillow block to support the outboard end of the final drive chain sprocket shaft to take care of the overhung load.

Best regards,


RE: A poor man's right angle drive?

"Commonly known as a CIG locker!"

I've also used the term Lincoln Locker (Lincoln Welders)

RE: A poor man's right angle drive?

It's March now so you've probably done something by now. I made many winches of Ford rear ends for the fishing industry. The spider gear rigs would eventually sieze, dangerous. The better rigs had the side gear that the axle fit into welded to the ring gear. You can choose rotation by which axle you use, if the unit is upside down, move the vent.  Remove all the spider gears. Don't get weld(or spatter,I made a shield)on the gear mesh area. Don't get the bearings dirty. This is hardened steel, use 7018 rod, preheat. Slug if necessary, but stay balanced. If the rear end is running in reverse, it may leak at the pinion if it has only a spiral and not a seal. Shortening the axle weakens it, and is not easy. We ususlly only used one axle, closed off the other end close to the banjo housing. Don't worry so much about an outboard bearing at the axle, that bearing is tough. Make safety guards. Go hydraulic as soon as you can afford, it's better.

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