LSD ideas

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LSD ideas

Postby New Guy » Tue Jan 07, 2014 4:32 am

I just read through the entirety of BADNEW5's 700awhp or bust thread, and watched the two videos right at the end of his grenaded center diff.

I spend most of my time doing 4x4 and offroad type stuff, so when I saw the vid of his diff (I've not yet been that far in to my SV25) I realized something...

The machinework for a helical LSD would be damn near impossible. A clutch type LSD is rumored to be available through Australia but that's some serious money... I don't think anyone has thought of a ratchet-type LSD.

They're most commonly used in 4x4 stuff, as under power they are a positive-engagement spool and when coasting they disengage and ratchet (hence the name) and allow the two sides of a differential to rotate in opposite directions or at different speeds. Basically exactly what we want; the VCU makes up for that little bit of slip we would need when turning under power, so our ideal arrangement is positive engagement between the transmission and the VCU under power.

I don't know how many of you have seen what a ratcheting LSD looks like, but they're very simple. They are usually composed of two high-grade steel slugs that replace the spider gears in a differential and they have little nubs that engage the side gears. When I saw the vid BADNEW5 posted, I instantly recognized the guts of a standard open differential.

If we could find a company that could machine just those two center pieces (I forget off the top of my head what they're called) to replace the spider gears, we could effectively have an LSD center diff with a very simple - and stout - package.

BADNEW5's videos:
http://www.youtube.com/watch?v=UwFToHUCFZ8
http://www.youtube.com/watch?v=UWXdrpdJA6U


Standard Detroit EZ Locker (with epic Paint text pointing out the engagement method/function of parts)

Credit goes to Detroit for unmodified pic.

Image



I know this will probably get torn to pieces, but all of the potential group buy threads I've seen were for far more complicated LSD setups. The ratcheting locker is a very simple way to get a basic LSD. I'm posting this in the general chit chat forum just to get the idea out there, not because I think everyone will jump on the wagon.

I'm not sure what it would take to machine a simple set just for testing purposes (the real deal is a hunk o' forged steel, very pricey initial setup) but I don't think it would be that bad. The advantage to these is that they *only* replace the spider gears (the tiny ones that ride on the round bars you can see in BADNEW5's videos) and utilize the stock crosspins (there are five in a 'Trac center diff) for engagement.
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Re: LSD ideas

Postby BADNEWS » Tue Jan 07, 2014 1:49 pm

Everyone who doesn't know how our AWD system works can watch this boring but informative video:

http://youtu.be/hMCJibC7nbA

After that here is the problem. Which might not be a huge one. Check this picture out:

Image

As you can see the side sun gear for the front diff IS the front diff housing. So with the Ratchet type LSD they would have to machine a whole new front diff housing. Now no one on the board was complaining about needing a center LSD. Everyone want a front LSD! Which your idea might work.


This is with the front diff still inside part of the center diff housing so it may lose a 1/2 inch. I still need to pull it out of the housing. I'll take more photos when I do.

Image

You can see you would have to machine in the spline teeth for the shaft of the Viscous Coupling to be able to connect to it if you had to do the housing for some reason. The long shaft sticking up is what drives the front right wheel from the front diff. But that can be pulled out. So it is a normal sun that the shaft splines into.

Image

This is with the front diff pulled out looking at the front left wheel sun gear.

Image
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Re: LSD ideas

Postby New Guy » Tue Jan 07, 2014 2:08 pm

With a ratchet style locker, the side gears (what you are referring to as the sun gears- different terminology from different crowds) remain completely unchanged. I have a diff outside of a housing with one of these installed, I'll try to get it (it's ~300 miles away) and take a video of me disassembling it. The only thing replaced by this style of LSD is the spider gear set. They run rough compared to a helical LSD but they are strong.
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Re: LSD ideas

Postby BADNEWS » Tue Jan 07, 2014 2:15 pm

You have my attention. I would love to see more of this now!
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Re: LSD ideas

Postby New Guy » Wed Jan 08, 2014 12:12 am

The earliest I could get a pic is next weekend, as I have some parts that need to be shipped soon but if they can't be shipped on time I will have to drive out to pick them up.

We had someone bring in a rig that got a locker installed but I was under a different vehicle when that was assembled or I would have gotten pics.


Also, I apologize for getting the front/center mixed up (as far as who wants what) as I've never really paid attention to it until now. My 'Trac is a daily more than anything else, so I don't really need improved track performance. If these become a reality, however... Well, let's just say your average ratcheting locker is about $250 shipped to your door. Probably closer to $400 for one of these as it wouldn't be an active production run.


Edit: http://www.youtube.com/watch?v=kL0hPEOStGk The guy in that vid does an okay job explaining how a ratcheting locker works. He doesn't use an open diff to compare the differences but you should get a general idea of how one of these could work in the limited space of an All-Trac front/center diff.
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Re: LSD ideas

Postby underscore » Wed Jan 08, 2014 1:34 am

You've got my attention as well, especially in the price range of $400.
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Re: LSD ideas

Postby alltrac101 » Wed Jan 08, 2014 2:03 am

That's like a phantom grip which basically loads the spider gears with springs pressure. Road racers did this mod back in the day because it was a simple & cheap solution to a real LSD.. the problem is our front diff is so small it has to fit into a main diff housing the size if a standard cage that is used for the mr2/v6 camry, plus it has a ring in the center for the front shaft output to pass through....
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Re: LSD ideas

Postby New Guy » Wed Jan 08, 2014 3:35 am

Most differentials have an open core; the ring needed for the output shaft to pass through is no big deal.

I can source these for $80 a pop through one of my boss' connections through China, but that would require a 10k unit order at a minimum. If we could find that many 'Trac owners... No problem.

These are stronger than the stock spider gears when configured properly, as you have more engagement with the side gears than just a couple of teeth at a time; the entirety of the side gears is engaged.

I would really need to gauge interest and have a prototype unit built to be sure (I would not go for a full-forged unit to test, I would have one machined out of high-grade steel to see if the concept is feasible. Setup costs to produce these are quite high).

I can get a long-term prototype forged in the $12k range. I make not a great deal more than that in a year so I wouldn't be going that route. I need to get access to SolidWorks and draw one, then see what it would cost to have one cranked out on a CNC. This could all end up being a pile of hot air; I honestly have no idea who I would talk to Stateside to have these built, I've never set up any sort of a group buy, none of that sort of stuff. I really just posted this to get the idea out there.

Heck, there's always the cheapy option of a Fozzy locker, which is a mix between a spooled diff and an open diff. You get ~1/4 turn free play and then it locks up. I use a setup like this in my current daily and it isn't so bad. It'd probably get tiring in a dedicated street vehicle though.
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Re: LSD ideas

Postby athousandleaves » Sun Jan 12, 2014 4:28 pm

Haven't read the whole thread yet but I think this should be posted in here too;

A ratcheting locker wouldn't be useful in a performance application for driving on a track or in a rallye as they put 100% torque to the wheel on the INSIDE of a turn while the OUTSIDE wheel is allowed to slip until its able to lock again.

Guy even explains that in the video you posted.

I looked at a lot of this off-roading stuff back when we were first tempted by an LSD a few years back.
None of it is really useful or applicable for driving on road or on a track at speed.
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