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trackfodder
05-31-2014, 10:48 PM
I was musing over a Berkeley sports car I used to own with a clever differential. It was powered by a 328 CC motorcycle engine . The differential was a drum that had a roller chain sprocket on it. Inside were 2 straight-cut axle-half gears connected by 2 pairs of small long gears on opposing sides of the drum. They were meshed with each other and one meshed with one axle-half gear and the other with the other side axle-half gear. The halves were spindled in bearing blocks.

dfw5914
05-31-2014, 10:54 PM
Gonna need some sort of illustration on that one.

darryl
06-01-2014, 12:20 AM
spur gear diff

fixerdave
06-01-2014, 12:54 AM
from: http://ycraf.blogspot.ca/2010/06/differential-render.html
http://3.bp.blogspot.com/_rWFbR0PSb4Q/TCvopN_xwTI/AAAAAAAAAKc/GptFb-IzHsA/s1600/differential.jpg

I was looking at it to see about doing something for an electric ride-on truck for my kid. There are a few designs floating about, though I think the output axles will need a lot of support. I do like the design as there's no gear movement when going straight. The gears only roll when there's an... um... differential :) I was toying with throwing the entire thing in a PVC pipe with a belt grove at one end instead of a sprocket.


If there's something simpler, I'd like to know about it.

David...

edit... you know, making 4 of those end-mounts with some space in-between would give 2 bearings per axle. The thing could be in a tube the whole length between the frame with the axles then going through a couple of standard pillow blocks then to the wheels. That would be rigid enough to resist the side-load from the sprocket/pulley.

Boostinjdm
06-01-2014, 02:03 AM
The most simple diff I have ever seen was in my RC cars. Specifically an Associated RC10 GT. It was the main drive gear in the center was drilled with several radial holes. The holes held ball bearings. That assembly was sandwiched between to plates. The plates had the drive yokes for the axles on them. Everything was held together by a bolt through the center. I don't know if this design will scale up well, but it is dirt simple and could be made in a home shop easily.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTUV6hz-M8pNoy8rduxRWTM6soVpgmjJAqYkZQa3EskXdMo2B8HAw

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcS4Q7KN9vFcyoJeuhKNet_PmhMScZj7_ pHND2vGqGe69ZkGKbt_

Mike Amick
06-01-2014, 02:15 AM
Hey Boostinjdm

Thats cool and simple .. but

How does that thing work. Can't see how that allows one wheel to turn at a diff rate than
the other.

Mike A

fixerdave
06-01-2014, 02:53 AM
...
Can't see how that allows one wheel to turn at a diff rate than
the other.

Mike A

The ball-bearings can rotate in the gear that drives them. Thus, as they also friction-drive the plates that drive the axles, one plate can turn faster while the other slower. I suppose avoiding friction between the gear and balls, while maintaining friction between the balls and plates might be an issue. Then again, like the spur gear diff, nothing really needs to slip when going straight. In scaling up, I think the main problem would be maintaining the force to keep the balls driving the friction plates. Probably need a lot of it.

David...

Black Forest
06-01-2014, 03:41 AM
The most simple diff I have ever seen was in my RC cars. Specifically an Associated RC10 GT. It was the main drive gear in the center was drilled with several radial holes. The holes held ball bearings. That assembly was sandwiched between to plates. The plates had the drive yokes for the axles on them. Everything was held together by a bolt through the center. I don't know if this design will scale up well, but it is dirt simple and could be made in a home shop easily.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTUV6hz-M8pNoy8rduxRWTM6soVpgmjJAqYkZQa3EskXdMo2B8HAw

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcS4Q7KN9vFcyoJeuhKNet_PmhMScZj7_ pHND2vGqGe69ZkGKbt_

Take this design and mount two sets of ball bearings. Have holes in the axle flange as well. Spring load the axle flange on each side to apply pressure to the center. Play with the spring pressure with an adjustment nut to apply more or less pressure. This is how some drill clutches work.

The Artful Bodger
06-01-2014, 06:30 AM
Incidently I am right now involved in the renovation of a Kerrison WWII anti aircraft gun predictor which is a big heavy box of gears and umgubbins intended to assist the aim of the gunners.

http://upload.wikimedia.org/wikipedia/en/thumb/d/d0/M5_director.jpg/440px-M5_director.jpg
This is an American made version but quite like the original.

There are two analogue computers, of sort, in the box based on ball and disk integrators and magical little assemblies which include a stage or two of those spur gear differentials.

Weston Bye
06-01-2014, 06:53 AM
The current Dodge (Ram) Power Wagon uses a spur gear differential.

kitno455
06-01-2014, 08:06 AM
The Austin 7 used a spur gear diff, and most of the full time 4wd transfercases do too, including the NP-242 used in jeeps/hummer, etc.

allan

Noitoen
06-01-2014, 08:49 AM
Here are a few examples http://www.stirlingsouth.com/richard2/south_pointing_penguin.htm

John Stevenson
06-01-2014, 09:51 AM
I was musing over a Berkeley sports car I used to own with a clever differential. It was powered by a 328 CC motorcycle engine .

I used to have one with the Royal Enfield 70cc Constellation engine in it.

Not though about if for quite some while, mine you it was a bit of a nail, more fibre glass repair than car.

ironmonger
06-01-2014, 09:59 AM
Another type:

http://www.freepatentsonline.com/6722484.pdf
figure 4a of the pdf shows the principle operation.

Kind of a 'Detroit locker' action. It doesn't divide the power, just makes sure one can overrun without scrubbing, or if the faster wheel loses traction the axle will speed up to drive the inner wheel as long as the outer wheel is has no traction. This is a bidirectional version of the starter drive I first saw in Japanese motorcycles years ago.

paul

A.K. Boomer
06-01-2014, 10:00 AM
I used to have one with the Royal Enfield 70cc Constellation engine in it.

Not though about if for quite some while, mine you it was a bit of a nail, more fibre glass repair than car.

SJ I think you missed a zero, or at least I hope you missed a zero or you would have been going nowhere very very fast....


Bare in mind it's also British CC's so that would put you at about as much HP production as "normal peoples" 45cc engines of the time...

Edit; ( Clumsy Bastard... )

MrFluffy
06-01-2014, 10:57 AM
I was looking at it to see about doing something for an electric ride-on truck for my kid. There are a few designs floating about, though I think the output axles will need a lot of support. I do like the design as there's no gear movement when going straight. The gears only roll when there's an... um... differential :) I was toying with throwing the entire thing in a PVC pipe with a belt grove at one end instead of a sprocket.


If there's something simpler, I'd like to know about it.
.
The majority of sit and ride lawn tractors have a pulley in the wrong plane to use, but if you search enough, some do have the arrangement to suit what you need.
I have one here, chain driven axle with a diff inside from a older massey ferguson rebadged lawn tractor. And drive chain from the diff outer up to the gearbox, then conventional pulley thereon in. I've got it stashed in the corner of the barn complete with big fat lawn tyres while I find a small electric start motorcycle engine to repower a disability scooter with to pull my dragbike back after a run.

You can't get simpler than just repurposing a complete bolt on unit with the bearings /shafts etc already done.

Lew Hartswick
06-01-2014, 11:13 AM
I was musing over a Berkeley sports car I used to own with a clever differential. It was powered by a 328 CC motorcycle engine . The differential was a drum that had a roller chain sprocket on it. Inside were 2 straight-cut axle-half gears connected by 2 pairs of small long gears on opposing sides of the drum. They were meshed with each other and one meshed with one axle-half gear and the other with the other side axle-half gear. The halves were spindled in bearing blocks.

HEY!!! welcome to the "group" > I had one too. Wish I still had it. It was yellow. Unfortunately it got
caught between a big old Mercury and the side of a bridge during an icy bit of weather. The only real problem I had with it was the middle plug was always getting fouled. You don't need a (I think it's)
a 5/16 Withworth wrench do you??? :-) Do you have a good pix or so of it ? I'd love to have copies.
...Lew...

John Stevenson
06-01-2014, 11:21 AM
SJ I think you missed a zero, or at least I hope you missed a zero or you would have been going nowhere very very fast....


Bare in mind it's also British CC's so that would put you at about as much HP production as "normal peoples" 45cc engines of the time...

Edit; ( Clumsy Bastard... )

Yup should have read 700cc, nice catch.
Mind you they weren't much of an engine either, big heavy thirsty and leaked oil where there were no joints.

Royal Enfield's slogan was "Made like a Gun " Mine were, they all went bang...................

http://www.stevenson-engineers.co.uk/files/royal%20enfield.jpg

MrFluffy
06-01-2014, 03:23 PM
Its because they were designed in the queens chicken shed ;)

small.planes
06-01-2014, 04:42 PM
Mind you they weren't much of an engine either, big heavy thirsty and leaked oil where there were no joints.

British built, if its not leaking its empty. Saves time checking the dipstick :p
Having said that my new (20 year old) truck doesnt seem to leak oil, or rain!

Dave

boslab
06-01-2014, 06:05 PM
Leaked like a Norton was a remark on a report in work about a henan drive unit on a caster turret, mind it was shifting 1500 tons, not sure if i spelled henan right, it was am air motor connected to a generator to rotate the turret during power failure, thought the comment was funny though.
Mark

michigan doug
06-02-2014, 04:43 PM
I believe the ball bearing r/c differential is just a clutch. Going around a corner, it allows one wheel to slip compared to the other wheel. Simple, effective, a little primitive.


doug

CarlByrns
06-02-2014, 04:55 PM
I believe the ball bearing r/c differential is just a clutch. Going around a corner, it allows one wheel to slip compared to the other wheel. Simple, effective, a little primitive.


doug

The ones I've seen work just like an 'open' automotive diff- spin one wheel and the other one will rotate in the opposite direction.

darryl
06-02-2014, 09:12 PM
It is an actual differential. The balls spin to accommodate the different speeds between axle shafts. In a straight ahead condition, the balls don't rotate- they turn the respective axle shafts by friction.

Imagine the balls had 'teeth', and the corresponding drive washers also had teeth- now there's no friction drive required, but the action is exactly the same as a bevel gear diff.