I was wondering peoples opinions on L.S.D.s. I am starting to design the diff for the 2010 ASME Moonbuggy competition. This is a lightweight human powered off road vehicle. Which type of L.S.D. would be best and why in peoples opinion? I am leaning towards clutch type.
Why not locked/spool on a moonbuggy? Lighter, more efficient, less complex, and smaller. With human power you won't be going fast enough to necessitate slip/open diffs for safe handling and you'll want to maximize traction so as to not waste energy spinning wheels. Is this 2wd or awd? What kind of propulsion method?
You may want to stay open or have a lockable diff in the front to reduce turning radius. With such lower power input, our locker could be something as simple as a sliding pin mechanism.
Bryce
We will hit a top speed of about 30mph. I was also considering a locking diff. Why would lockable or open diff reduce turning radius.
Unless you recruit a pack of savages, you won't have an abundance of power to cause wheel spin. Anything in the automotive realm would be too large and complex. You don't want all that extra driveline mass either. I would look for an ATV limited slip if you have your heart set on one. You can find them in clutch and locker type LSD's. If you want simple, run a spool.
We are planning on building it ourselves. I know that sounds insane but we have the ability. The biggest problem is that if it rains there is a part of the coarse that becomes extremely slick.
Is an LSD actually necessary? Concentrate on keeping your wheels on the ground, and with your low power levels it may not be an issue. You know more about what you're doing than I do, of course.
A locked front diff will make the vehicle want to plow really badly. It basically removes steering as an option.
Part of the track is a coated concrete that gets very slick in the rain. A lot of the teams had trouble with traction at the 2008 competition on this part of the track. The 2009 buggy is about to hit the test coarse and so I will soon see if traction is a issue anywhere else of the track.
Maybe I'm not with you 100% here. Why not attach a sproket to a solid axle, hook up some wheels to it, and be done?
LSD types... let's see....
Like, wow, man...There's the type that makes the pretty colors, the type that makes everything spin round and round and round, and the type that...Oh, wow...what where we talking about?? 
Sorry- couldn't resist. Back to your regularly scheduled thread.
this could be easier than you think...
take two freewheeling single speed rear hubs and connect each axle half shaft to each one. The main drive chain comes down to a duel sprocket with a small chain to power each halfshaft.
taking a corner, the outside wheel has to spin faster than the inside, so it goes into freewheeling mode with little loss of power
You could try something from the go-cart world:
http://www.mfgsupply.com/m/c/218239A.html?id=CkAKgjDV
A little pricey, but easily adapted to sprockets, belts, etc.
Carter
With such low power levels I think a lack of traction is coming from your tires as oposed to an open diff. Do you know what diff's previous teams used? If you need the super tight turning radius, then go with a lockable open diff, other wise throw a spool or solid axel and go look at apropriate tires. With such little weight you arn't getting much friction so some gumballs with water tread might work.
mad_machine wrote: this could be easier than you think... take two freewheeling single speed rear hubs and connect each axle half shaft to each one. The main drive chain comes down to a duel sprocket with a small chain to power each halfshaft. taking a corner, the outside wheel has to spin faster than the inside, so it goes into freewheeling mode with little loss of power
That's an excellent idea! Probably worthwhile to take it further and make it awd.
You'll lose efficiency every time you go from gear to chain to gear - and I don't see how that's an LSD. Sounds like an open to me. Although if you use coaster hubs, there's your braking system as well 
You may not need a LSD if you have the capability of braking the driven wheels individually.
There used to be a kit for manx style dune buggies that used a seprate e-brake for each rear wheel. It was intended to be a poor man limited slip... It ended up being used for hoodlimism instead 
Capt Slow wrote: You may not need a LSD if you have the capability of braking the driven wheels individually. There used to be a kit for manx style dune buggies that used a seprate e-brake for each rear wheel. It was intended to be a poor man limited slip... It ended up being used for hoodlimism instead
Sounds like you're referring to a "cutting brake" which is very common in the dune buggy world as well as tractors and such. It helps to tighten up the turning radius, which is especially helpful with dune buggies in the sand that are rwd with big huge paddles in the back and skinny tires up front. It's not an ebrake, it goes in line on the hydraulic line to each brake. The one-handle design is made so if you push you brake one side, if you pull you brake the other side. The two handle units use a left handle for left brake and a right handle for right brake.
Still sounds like overkill for a space buggy, but it at least clarifies the cutting brakes.
Bryce
No the buggy runs a inboard brake.
I am aware of the cutting brakes. This was a bit different in its marketing at least.
My dad had on his buggy when I was little. I am still mad at him for getting rid of the the buggy before I could drive it...
-- back on topic: This would be a fairly simple and lightweight solution...
Run a locked rear. an LSD will be added weight.
weight is everything on those moon buggy things.
Locked rear will most likely be your best bet. The over-running clutch idea sounds promising though.
Remember, in the original posting he said this was to be human powered. That really negates the effectiveness of cutting brakes and such, while making the use of bicycle parts much more reasonable. If for nothing else, they'll be strong enough while being light.
And a spool will seriously hurt turning radius and create a lot of friction for low-speed turning, not something you want with less than 1 horsepower. Even a clutch type diff would create too much drag.
Back when I was doing RC cars, there was one called a Schumacher CAT which was 4wd. Instead of a conventional differential, it used 'one way' bearings at the inner end of each of the front drive axles, very similar to a ratcheting rear hub like as is used on a 10 speed bike. They would lock up when power was applied and freewheel in a turn.
Another diff type you might consider is a 'ball type', again from RC cars. It's not a limited slip type diff but it's pretty simple to build and is adjustable.
If you're going to be building the diff from the ground up and you only need a limited-slip capability in a particular potential situation (rain) that you can predict with good accuracy before your run (either the course is wet or it isn't), why not run an open diff but design it with a simple manual locking capability like a pin or a few bolts that you can insert in case the need arises? No driveline loss from extra complexity, and you've got an open diff unless you need otherwise.
It rains on the moon?
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