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 Post subject: Chain drive differential
PostPosted: Fri Dec 05, 2008 5:35 pm 
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So being a car and bike guy I have experienced changing gearing in both. I have sat and swore up and down the garage while regearing my old wrangler. I have also made quick track day gear swaps on the R1 that took a matter of minutes.

I have been back and forth on my ideas for Chain driven vs. propshaft automotive differential driven more then McCain uses the words "my friends" in a speech :lol:

So here are some conclusions for people like me.

Prop shaft and automotive differential
This is probably the easiest way to go as it can be a simple bolt in type application using a miata or like subframe and axles, or it can get a bit more complex with a Quaife reverse box, ect. It is going to be the most reliable option as it is designed to handle the everyday driver and power output of a 150-175hp motor. Basically its the hassle free way to go... until you want to change your gearing.

Most bikes run a sprocket ratio right around 2.7:1 and most car differentials are between 3.73 to 4.10 for 4 cylinder applications (shorter of larger motors 3.42+). To me throwing a 4.10 in with a bike motor isnt very appealing and piecing together a combo that incorperates a LSD is not becoming very Locost like. I have been exploring into the Mazda differentials world and i have come up with several donor differentials with LSD's that can be had for around $250 (like AirFrameRepairs setup), but then you have to find axle shafts that will mate, usually modify them, find corresponding uprights and all. Then if you want a lower gearset you need to source a truck with matching gears with a lower ratio, or buy a new set for $250+. By then end of the process i needed to buy 2 uprights, 4 half shafts, a LSD setup diff from a car, and one open diff from a truck. That seems like just too much junk yard hopping for me just to not be satisfied with my gearing choices.

So this time i went digging further for Chain Driven Differentials
Heres what i found, mainly from the other side of the big pond. If you want a differential driven by chain your going to need some key parts. Your going to need:
- 2 bearing carriers. One on each side to support the differential and allow it to turn. Many people will CNC them or use simple style bearings
Ex:
Image
or
Image

- 1 differential, preforably LSD with bolt on style Half shafts and CV's
(still trying to find a nice US one to use... please throw options out!)
Image

-1 home made welded or CNC'd "hat" for the differential. This slides over the diff up to where the ring gear mounts. Then the back slides up past when the bearing sits. usually the hat is bolted to the carrier to keep it in place and seal it with RTV. Then put a zirk fitting on the hat and pump it pull of grease. Grease will lubricate the LSD, Spider gears, or Torsion gears and wont leak out easy.
Image
Image

So basically:
1. buy a diff
2. CNC or weld up a hat that will seal in the differential. Make a small trap door to clean it out and also install a zirk fitting.
3. Bolt the hat to the differential by tapping two small holes into the carrier or something creative. Seal the edges with RTV.
4. CNC or with some other form create your carrier plates
5. Probably going to have to buy the stock diff side seals and seat them into your own outter brackets to seal the shafts
6. Put the shafts and and c-clips
7. Pump it full of grease

Seems perfectly feasible to me to build. There are people on the forums with the CNC capabilities and companies in different cities/town. Just draft out what you need done and they can probably make them for a decent cost. You can even adjust the tension in your chain by making one mount that bolts and one mount adjustable with right and left thread rod ends. The options are endless.

Here are some finished products that i have found that are more then feasible to do and in a locost manner.

Image
Image
Image
Image
Image

Heres some great links:
http://www.westgarage.co.uk/forsale/forsale.html
http://www.locostbuilders.co.uk/viewthr ... 246&page=1




So guys... where can i source a cheap differential to start this? i would prefer the innards or a used LSD or Torsen differential. It needs to be a differential that the CV's bolt up to like most the mazda ones. Then i can buy the output shafts and half shafts seperatly.

Oh and yea... this is basically a locost version of the quaife unit.

My plan is to build this and make a subframe between the motor and the frame that will carry it and have adjustability for chain tensioning. This should help in packaging of the Middy, changing of the gearing, inboard brake options, and cheaper reverse options.

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 Post subject:
PostPosted: Fri Dec 05, 2008 6:00 pm 
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found a bunch of 90-93 LSD's on ebay for $50-75

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 Post subject:
PostPosted: Fri Dec 05, 2008 6:24 pm 
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Location: Marietta, GA
You ought to check out Grassroots Motorsports' Berzerkley build. They had a recent article on fabbing a custom BEC differential from stock components.

http://grassrootsmotorsports.com/projec ... y/updates/

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 Post subject: Beserkely Diff
PostPosted: Fri Dec 05, 2008 9:00 pm 
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Location: Anchorage Alaska
Read the Grassroots Magazine article about building their custom diff with reverse before you think about that!

They said it took way, way too many hours to build even if you had all the machining tools, and stacks of gears and shafts to choose from.

And then it self destructed in the first autocross run. Not what you want!

The Quaife chain drive diff is under $850 at today's exchange rate but still a lot of money for us LOW-coster's. :roll:

I am using a Subaru Justy rear diff but it is not an LSD, just small, cheap, and relatively light. I think you can use just about anything you want but it is easier if you use what your axles, CV's and all work with without mods.

Then just build the carrier for bolt on bearings and your own hat.

I noticed that the Quaife unit has (4) zerk fittings equally spaced around the can for good lube distribution, good to keep in mind.

James 8)


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 Post subject: Re: Beserkely Diff
PostPosted: Fri Dec 05, 2008 10:44 pm 
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Location: Marietta, GA
JagLite wrote:
Read the Grassroots Magazine article about building their custom diff with reverse before you think about that!

They said it took way, way too many hours to build even if you had all the machining tools, and stacks of gears and shafts to choose from.


I was thinking the same thing, I just didn't want to crush his spirit! :o

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 Post subject:
PostPosted: Sat Dec 06, 2008 1:36 am 
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Location: San Antonio, Texas
i've been looking into the chain differential
and i have come up with the best set up
but u need a middy or rear engine layout for this concept that i hope to build after college

take the stock rear sprocket (bigger or smaller if u wish) and either weld a solid metal rod to it, or make a conecting system to attach the sprocket to the metal rod!
when u turn the metal rod u should be able to spin the sprocket!
next build a box out of thick gauge aluminum and some bracings to stop torsion flex.
hook up cv joints to the end of the metal rods.
hook the cv up to ur wheels

all in all the mid engine layout puts the engine close enough to this differential to use a chain! wrap the chain around the sprocket and let her loose! and best of all if u want to change ur gear ratios, either bolt another sprocket to the metal rod or weld up a new one!

it's the basic consept u have in picture number 2 in the first post!
this is the most versitule, cheap and lightest set up!
SHOULDN'T take long to build!?!
easy to change gear ratios (simply change the rear sprocket size)

disadvantage?
u have to build it!?!
and both wheels will always spin at the same speed (so it will be a handeful around corners, so learn to steer with your right foot)

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 Post subject:
PostPosted: Sat Dec 06, 2008 1:44 am 
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Location: San Antonio, Texas
also this has been talked about before,

but with the chain set up, if u want a reverse all u have to do is mount a starter motor with a sprocket to link into the chain, and rig it in a manor so that when u turn it on (bike engine in nuetral of course) it spins the chain backwards... this moves the sprocket in reverse (obviously :roll: ) and it will push the car backwards for u

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Educatio Est Omnium Efficacissima Forma Rebellionis

Education Is The Most Effective Form Of Rebellion

Is that what happens to us? A life of conflict with no time for friends… so that when it's done, only our enemies leave roses.
For my own part, regret nothing. Have lived life, free from compromise ... and step into the shadow now without complaint


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 Post subject: Re: Beserkely Diff
PostPosted: Sat Dec 06, 2008 1:45 am 
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Location: Subs of Detroit, MI
JagLite wrote:
I am using a Subaru Justy rear diff but it is not an LSD, just small, cheap, and relatively light. I think you can use just about anything you want but it is easier if you use what your axles, CV's and all work with without mods.

Then just build the carrier for bolt on bearings and your own hat.


This is exactly my plan... so why warn me? I think i may have come off way more complex then i wanted. Its actually a pretty simple setup, same as many FSAE teams use.

I skimmed the grassroots article and theirs is way more complex then i want to go. Im not planning to make it do reverse also... ill just do the ghetto winch motor reverse. Their box is cool in theory, but there is just too much room for flaw.

My plan is just a miata diff, miata shafts, miata uprights, build a hat, and either CNC two plates to accept the bearings or ill just do the bolt on style bearings...

This is just one of those projects i have to take an attempt at before throwing in the towel. If we just assume we cant do something, then we never will.

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2007 R1 Powered Mid Engine Street & Track Car
Build Log: viewtopic.php?t=4970
Quote:
On the cool points scale you rank just above Isaac Newton and just under Batman.


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 Post subject:
PostPosted: Sat Dec 06, 2008 1:56 pm 
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Assphalt Kicker wrote:
this is the most versitule, cheap and lightest set up! ...

disadvantage?
both wheels will always spin at the same speed (so it will be a handeful around corners, so learn to steer with your right foot)
This is actually a very significant disadvantage to consider. I also would not call this the "most versatile" option by any means...Simply the cheapest, easiest to build, and lightest.

This is known by numerous names like locked diff, spool, Lincoln (Miller ;)) locker, etc. It certainly has it's place in racing, but is really no longer a "differential" in function. It will work fine for drifting and dirt, and on larger radius/faster asphalt corners, but will not work nearly as well on tighter corners. The only thing it will really be better than in road racing or autox is an open diff in situations where you have corner exit inside rear wheel spin. It will induce corner entry understeer. While it seems to work pretty well on go-karts, they're a bit of a special case. Dragging the inside rear wheel around the corner is generally not going to help your overall grip, nor will it be very good for tire life on the street. If you've ever heard or driven a pickup with the rear locker sticking while turning in a parking lot, that's the ghettoness you'll hear and feel all the time on the street.

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Last edited by Driven5 on Sat Dec 06, 2008 4:37 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sat Dec 06, 2008 3:15 pm 
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Assphalt Kicker- a locked rear diff on a street car would be hell my jeep had a "miller" rear locker and it made any turns horrible. All you would hear is binding, tires screetching, and feel tire hopping.

Might want to take a ride in Car with one. I wouldn't call it "versatile" for the street, I would call it stupid. No offense.

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2007 R1 Powered Mid Engine Street & Track Car
Build Log: viewtopic.php?t=4970
Quote:
On the cool points scale you rank just above Isaac Newton and just under Batman.


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 Post subject:
PostPosted: Sun Dec 21, 2008 10:51 am 
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I had a Toyota Corolla KE30 that I rallied for about 3 years about 20 years ago with a welded diff and drove it around as a daily driver as well. No problem at all anywhere, anytime. True there was some scrubbing in car parks and theres is a difference from mid engine because the engine weight of course was up the front , not over the wheels but it won't be as bad as you think. A few Datsun 1600's I've driven with locked diffs are are a bit different because the wheels dont always steer in the same direction being a trailing arm rear suspension.

When I was about 20 one BEC I started to make used a diff that may be of interest. It was from an older 1500 VW Passat box I had laying around and was near perfect. The advantage being that it has bolt in drive flanges. I seem to remember a little light trimming of either the flanges or the diff side bearing carriers or both in a lathe to suit some cheap self aligning bearings in pillow blocks.

I didn't actually finish that car but I did finish the diff and it only took an hour or 2 all up.

My point is the VW seems a good choice because of the bolt in flange setup.


Last edited by cheapracer on Sun Dec 21, 2008 1:11 pm, edited 1 time in total.

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 Post subject: Re: Beserkely Diff
PostPosted: Sun Dec 21, 2008 12:24 pm 
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Location: San Francisco Bay Area
blue devil wrote:
My plan is just a miata diff, miata shafts, miata uprights, build a hat, and either CNC two plates to accept the bearings or ill just do the bolt on style bearings...

That's pretty much what this guy did...

Image

That's a Miata LSD diff mounted in a square tube 'carrier basket', with chain sprocket added to the left side CV flange. Miata axles and lower control arms. Miata uprights, brakes, etc., and 10 x 13 aftermarket wheels. The upper control arms are homemade to accommodate the coilovers.

Simple, effective and very cheap. I'll ask him to snap some better pics.

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 Post subject:
PostPosted: Sun Dec 21, 2008 1:57 pm 
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More pics would be great!

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2007 R1 Powered Mid Engine Street & Track Car
Build Log: viewtopic.php?t=4970
Quote:
On the cool points scale you rank just above Isaac Newton and just under Batman.


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 Post subject:
PostPosted: Tue Dec 23, 2008 5:52 pm 
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Location: San Francisco Bay Area
blue devil wrote:
More pics would be great!

I got an email back from the guy saying he will take more pics. Unfortunately, the only camera he has is in his cell phone, which took the photo I posted above.

I told him he needs to write to Santa... :lol:

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You can have it light, cheap and strong -- choose any two!


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PostPosted: Sat Dec 27, 2008 8:30 pm 
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Location: Brighton, MI
Chain drive works great. The pic shows a VW rabbit diff with a Tupperware bowl cover! Shortened VW halfshafts too. The only problem is the bearings. I had to sleeve the diff. Custom casting for the bearing carriers but then that was 20 years ago. Now I would have them CNC'd for the same money. The diff mounting frame bolts to the back of the engine and the whole thing is rubber mounted. Solid mounted diffs and engines suck. There are 5 others running around like this with no problems. The inboard brakes work fine as there is lots of air flow thru the engine compartment from the body side scoops. The car weights 1100# so the 10" Wilwood brakes are more than adequate. I have a new setup designed for my Hayabusa powered car that is much simpler but it uses an expensive chain drive race diff. It packages the sprocket outside of left diff bearing and moves the engine to the center line of the car. There are always trade offs!


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