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Mon Jun 15, 2009 9:50 am

Hello,

I have a 1968 VW Baja bug. I was wondering if there was a locking differential (LSD, vacuum, electronic, whatever) available for it?

Mon Jun 15, 2009 11:29 am

I think you can get one for a bus
but not a bug

Mon Jun 15, 2009 11:38 am

Seriously? I would have thought someone would make one for the beetle!

Mon Jun 15, 2009 12:19 pm

you can get a
factory vw ZF differential (limited slip)
Quaife (limited slip)
peliquin is making a slimited slip diff too.

plan on spending a minimum of $800 for a used one up to a couple/three grand for a new one

Mon Jun 15, 2009 1:41 pm

they can be had but at the price of an arm and probably one of your legs.
if you really need some kind of locker because of the kind of off roading your doing than i suggest a cutting brake.

http://www.mooreparts.com/store/product/2257/CNC452SB-34/

it will allow you to apply the rear brakes independently of each other which can help you get out of holes your stuck in and can make turn on gravel roads a lot of good old fashion dangerous fun.

Mon Jun 15, 2009 9:19 pm

A Quaife for a swingaxle is running about $1800 these days. They weren't even available for a long time, but I think Quaife made another batch. Most guys that use them are building really stout gearboxes and have about $3K into them.

Mon Jun 15, 2009 9:26 pm

I have seen these cutting brakes and like the idea. It wouldn't be too hard to rig up a hall effect sensor running to a board that measures RPM differential (or spike) from both wheels. A glance at a gauge of sorts on the dash will tell you which wheel is spinning, and which lever to pull up on.

I don't know if there are spider gears to weld, but I have never liked that option for anything that touches pavement anyway.

Mon Jun 15, 2009 11:24 pm

tundrawolf wrote: I have seen these cutting brakes and like the idea. It wouldn't be too hard to rig up a hall effect sensor running to a board that measures RPM differential (or spike) from both wheels. A glance at a gauge of sorts on the dash will tell you which wheel is spinning, and which lever to pull up on.

I don't know if there are spider gears to weld, but I have never liked that option for anything that touches pavement anyway.

welding spider gears is always an option but i prefer to do things right rather than the redneck way. :lol:

i like you idea with the sensors.
you know what would work for that? those little magnetic Bike speedos. you could run two and hook them up separately to each rear wheel. the spinning tire would yield higher numbers than the other.

Tue Jun 16, 2009 9:00 am

I know what you mean, the idea never sat well with me, wearing out tires quick, stressing drivetrain components..

I was thinking for the sensors, whatever frequency counter board one used, would have to have a fast sampling rate.

Something that could turn small milivolt pulses into milliamps could drive an analog needle-type meter, one meter per wheel.

I was also considering a simple LED light setup, one LED would glow showing one wheel spinning (Measuring differential).

A digital display showing actual RPMs would have to have a VERY fast driver, and even then (Have you ever tried to keep track of a fluctuating voltage a digital multi meter?) keeping track of the readings would be difficult.

Dave

Tue Jun 16, 2009 9:19 am

Keep it simple, With cutting brakes installed there is really no need to have electronic indication for which side is spinning. You just pull a handle and if you don't feel an immediate torque engagement you pull the other handle. Very little thought involved and no electronics to fail.

Tue Jun 16, 2009 9:28 am

I see...

How effective are they for hill climbs?

Tue Jun 16, 2009 9:33 am

How about an electric guitar pickup on each wheel, keyed off the CV bolts, through an amp to stereo headphones. You could hear which side is spinning or not.

..Ok stupid idea. :D

Tue Jun 16, 2009 9:39 am

You know the REAL interesting thing would be to delete the notification system and plumb in a control system to a high-torque plunger motor that actually activates the cutting brake itself.

Literally a "Traction control" system, found in many modern cars, in the beetle, and it'd be fairly cheap, and easy to do.

Something to do would be to go to a boneyard and find the traction control system actuator module off of a 'whatever', and use it in a bug.

It'd be a lot less complicated than it sounds.

Tue Jun 16, 2009 6:06 pm

For a indicator you could use an optical encoder or resolver. Connect it to a comparator circuit. this would show a positive or negative count if one wheel spins faster. then you could connect a spool valve to the brake circuit to add or remove pressure from one side. The more error between the two the more brake pressure to the slipping wheel.

I wouldn't run something like this on the road it would react when you go around turns at high speed

Tue Jun 16, 2009 6:35 pm

congratulations guys, you succeeded in making something as simple as a a cutting brake into rocket science. :lol:

Tue Jun 16, 2009 6:51 pm

strohma wrote: For a indicator you could use an optical encoder or resolver. Connect it to a comparator circuit. this would show a positive or negative count if one wheel spins faster. then you could connect a spool valve to the brake circuit to add or remove pressure from one side. The more error between the two the more brake pressure to the slipping wheel.

I wouldn't run something like this on the road it would react when you go around turns at high speed

I like this idea. If we could rig something up (It wouldn't be too hard to have a "Traction control" switch on the dash) it'd be one heck of a write up.

I am personalyl leaning more towards a hall-effect sensor, because in the event fo mud, it will not affect a reading.

Runslikeapenguin, you are right, because it would have to only put so much brake pressure on at certain speeds (Imagine a wheel lock up at 65 MPH on the dry lake bed).

Still, to me it would be worth looking into. Not too hard to get it to be disabled at certain speeds (More than 25 MPH?).

Tue Jun 16, 2009 7:51 pm

runslikeapenguin wrote: congratulations guys, you succeeded in making something as simple as a a cutting brake into rocket science. :lol:

What, you mean there is an easier way to do this? You obviously aren't thinking like an engineer, if it works it probably does not have enough extra features. :D

A microprocessor-based controller circuit would be quite simple for this purpose. You could have an electronic cutoff programmed in for a certain speed (with a manual backup). Then all it has to do is translate the sensor input into either lights (easy) or mechanical output directly to the cutting brake (not very complicated with a MOSFET drive circuit). Heck, I'll bet there is a specialty IC out there somewhere factory-programmed just for this..

Tue Jun 16, 2009 8:11 pm

Like a STAMP? A rotary optical pulse generator would be ideal for linking to the speedometer cable (or internal speedo mod) because there is no mud/debris to get in the way.

I like getting the traction control actuation module (Like the ABS module) out of a vehicle, because it would have the motor/plunger network to properly put pressure on the brake drum of either side.

If need be a regulator could be used.

This is absolutely do-able.

Tue Jun 16, 2009 8:14 pm

yellow73kubel wrote: runslikeapenguin wrote: congratulations guys, you succeeded in making something as simple as a a cutting brake into rocket science. :lol:

What, you mean there is an easier way to do this? You obviously aren't thinking like an engineer, if it works it probably does not have enough extra features. :D

ohh im thinking like an engineer alright, but im thinking old school. personally i think over engineering of simple systems is whats killing reliability in modern vehicles. i also believe it to be one of the main reasons we have an ever increasing amount of highway accidents despite the advances in modern saftey technology. but that's a topic for another time.

im a fan of keeping things manual. if the driver can program himself to perform the task you need done why would you go out of your way to add an unnecessary system to an already functional one? IE the driver.

remember the ultimate machine would do everything instantly as simply as possible with out using any energy.

Tue Jun 16, 2009 9:00 pm

I TOTALLY hear you, runslikeapenguin.

I am actually looking from the "I don't want to spend over a grand for a hard to find locking differential so I can have a good 4x4 so to speak".

I hear you, though, and agree.

You ever hear of an EMP bomb?

In the event of one of those detonated over our country, the only things on the road will be our points VW's and my 1979 LUV truck!

:lol: