gear sets for over/under drive unit

[modifiedoutboard]

Anyone know of gear catalog with spur or internal gears suited for over/under drive unit.
By ganging three around the input and output shafts (semi planitary)
makes for a possible off the shelf gear application.

Thanks in advance for your value added comments as well as for the other kind too!

[bill van steenwyk]

Might be less expensive to consider......

a mechanical torque multiplier used to increase the torque of a manual torque wrench. For an underdrive application it might be possible to drive it from the output end rather than the input end, as it is designed to be used in bolting applications. These in sizes up to 500 ft. lbs capability are very small considering the torque they can develop and withstand and might meet your needs rather than spending all the time and effort required to machine a special housing, etc. Snap On tool makes several and I am sure there are lower cost imports available now from Asia. Just Google "mechanical torque multipliers" or "air driven torque multipliers" (some are driven by air motors to decrease the nut run down time) and you may find something that would work for you with less time and effort, especially if you want a planetary gear set.

[ram95]

I'll just offer this. Not many of you out there have disassembled one of the newer "hi-torque" starters which have just such a set of planetary gears.... they are incredibly small... and plastic to boot. Yet they can transmit enough torque to start a big block GM marine engine on a cold day. I have to wonder though.... just how would these gears handle a shock load of a prop out of the water and suddenly into the water.

Alex

[A/B Speedliner]

Gears

The reason the non metallic gears can work in the starter motor is they are not run for any great length of time. Maybe 10 to 15 seconds. Try running these for 10 minutes under load!!!
David

[ram95]

planetary gears

The reason the non metallic gears can work in the starter motor is they are not run for any great length of time. Maybe 10 to 15 seconds. Try running these for 10 minutes under load!!!
David

Guess my point was to agree that the planetary gear idea has a lot of merit. I just wonder if it could be made to hold up. I'm always amazed at the strength-of-materials when things are correctly engineered. Our battery powered impact wrenches and screwdrivers being an example of planetary gear designs that hold up even when abused.
Alex

[krazy karl]

Gear Vendors

Look at the size of a Gear Vendors overdrive unit for diesel trucks. Not a large unit but is built to handle gobs of torque. Some diesel hot rodders are getting 1,000 lbs of torque or more and these units hold up just fine.
kk

[blueskyracer]

all automatic transmissions in trucks and cars have a planetary system in them. Like it was said if they are designed and made with the right material it should work.

[sam]

I had not thought of a truck overdrive unit, but have been wondering for a few years about the smallest car auto transmission planetary. You'd think there are some pretty small units in some of them ... just waiting at the junk yard to be converted. I'd really like to have a planetary between a big inline 6 and a Speedmaster ... fwd, neutral & reverse

Planetary transmissions were used in cars long before automatic transmissions ... the 2 fwd speeds & reverse in a Ford Model T are via a manually operated planetary transmission. There are 3 pedals and a hand lever to control it and the rear wheel brake band mounted on the back of the transmission.

[Dan M]

If you're still looking for gears to make your own, take a look at
http://www.bostongear.com/

They may even have a planetary drive available.

Dan

[modifiedoutboard]

thanks

If you're still looking for gears to make your own, take a look at
http://www.bostongear.com/

They may even have a planetary drive available.

Dan

There is an existing 20% 0r 25% in-line planetary out there some where.......
I have seen a small 25% inline-bolt on overdrive for an MG car once.

Boston Gear is where I was heading for off the shelf gearsets.

The concept design pics are really not planetary as such but a inline drive
with three gear sets arranged radially around the input and output shafts.

This distributes tourque kind of like a dual pinion speedmaster and makes it possible to keep it small and use stock gears.

I am looking at:

off the shelf:

5 simple 1/2" shafts
8 inexpensive off the shelf gears
10 bearings
2 seals
2 o-rings
off the shelf fastners

Machine parts:
2 back plates(percision machine part)
1 round housing(percision machine part)

Thinking all of the above around $1000

[johnsonm50]

Guess my point was to agree that the planetary gear idea has a lot of merit. I just wonder if it could be made to hold up. I'm always amazed at the strength-of-materials when things are correctly engineered. Our battery powered impact wrenches and screwdrivers being an example of planetary gear designs that hold up even when abused.
Alex

For many years I abused the heck out of a Millwaukee screw gun meant for wallboard installation. The clutch drive was 2 plates with gear teeth on the sides that were sprung apart so the motor could free wind & slammed together under load each time a screw was rammed in. I used to purposely slip the clutch with socket on to shake stubborn bolts loose & to push harder on screws that dared resist. Being a tradesman this was an every day 'driver'. Its still good after more than 10 years of hard labor.
Of course these are some variety of strengthened steel but as you say the hold up factor of some materials is incredible. Id think that type steel could do whats needed in a planetary situation. If you look into tool gearing there might be hope.

[wolfgang]

Splendid idea Anthony. Try Cyclo or Bonfiglioli. Best regards,Wolfgang

[alanaker]

?

You may be able to make one of the planetary sets from one of the autotranny merc fishing motors work. (Mark 28, etc...). Hubbell made one like this years ago. Not too long ago I noticed an overdrive unit someone had built into the bottom end cap of a 4 cyl. Merc with parts like this.