Ring & Pinion

[aeronca65t]

I find I'm getting about 10 events out of a ring and pinion these days. To me, that's not too bad.....used replacements are cheap and pretty easy to find. I'm swapping out the entire differential and not just the ring & pinion.

I actually "caught" this one just before total failure. The pinion is severely worn and there is a ton of "slack" between it and the ring gear. These differentials are old and well used so I'm not complaining. Honestly, I think it's the sticky race tires that are causing the failure. Not much to be done about that.

The differential I'm replacing is from the Sprite I drove in college (45 years ago). I know because it's welded and that's the only one I've ever welded. I only put it in because I had no other spares at the time (I've collected a few more since then).
Over the years, I have generally preferred a normal "open" diff and that's what I'm putting in today. I like them at least partly because the car is easier to push around in my driveway

I used to snap axles (outer end) until I switched to double-bearing hubs. Now axles seem to last quite a long time (I just use stock axles). I also added Speedi Sleeves a few years ago and that seems to have stopped (most) gear oil leakage into the brake drums. Just put new rear shoes and wheel cylinders in too so things should be OK for a while. I hope.

The car is resting on jack stands, but I also left the lift jacks in place. Plus I put the tires under the car just in case. Belt and suspenders

 

[AN5Sprite]

Thanks for the info.

How long do ribcase transmissions last you?

 

[nomad]

Soooo, If I'm hearing this right, a big horse power increase would be hard on axles AND rear end's!

Kurt.

 

[aeronca65t]

Steve: Ribcase gearbox seems to last forever. Same one now for 6 years (about 50 events). My street Spridgets were the same. The one I have in my current 948 street Midget is from my college roommate's car (again, about 45 years ago). It made a racket in 1st gear back then and it still does. But works fine. Change oil every year or two and they are very sturdy. I'm a huge fan of the ribcase and prefer the feel of it to the various 5 speed replacements that are in vogue.

And yeah, Kurt, part of this is because my car has a mild engine (estimate about 75 HP). I've clocked it (GPS) at 102 MPH with a 4:22 final drive so it's got a small amount more than stock. One of the guys that races with us has an old Craig Chima Spridget. The rear alone in that probably cost at least $6000 to build.
Some of the FISC Spridgets in the ~FISC/Eurotour~ series have 1410 cc engines with almost 200 HP and can run 145 MPH. I'm guessing they have studier final drives and axles.

 

[nomad]

Steve: Ribcase gearbox seems to last forever. Same one now for 6 years (about 50 events). My street Spridgets were the same. The one I have in my current 948 street Midget is from my college roommate's car (again, about 45 years ago). It made a racket in 1st gear back then and it still does. But works fine. Change oil every year or two and they are very sturdy. I'm a huge fan of the ribcase and prefer the feel of it to the various 5 speed replacements that are invogue.

And yeah, Kurt, part of this is because my car has a mild engine (estimate about 75 HP). I've clocked it (GPS) at 102 MPH with a 4:22 final drive so it's got a small amount more than stock. One of the guys that races with us has an old Craig Chima Spridget. The rear alone in that probably cost at least $6000 to build.
Some of the FISC Spridgets in the ~FISC/Eurotour~ series have 1410 cc engines with almost 200 HP and can run 145 MPH. I'm guessing they have studier final drives and axles.

I have a Datsun built with 5 speed I was going to swap into a car with a supercharger. Estimate around 100hp....might not be as good an idea as I thought.

Kurt.

 

[aeronca65t]

You may be OK. There are plenty of street Spridgets with 90 or so HP.

And street tires are pretty hard so it may not be that much of a deal. They are less likely to "hook up" and will spin easier.....which will reduce the ultimate load.

Typically the UTQG number (relates to hardness) for street tires is 300 or 400 (or more). My R888 race tires are much softer with UTQG number of about 80.

 

[nomad]

I've got too many other projects right now anyway and the engine is gathering dust. I will give it a try down the road! Lotus is taking precedence!

Kurt

 

[AN5Sprite]

Nial, I'm just curious... Are you using a lightened flywheel in your race car? If so, what's the weight?

I'm thinking of going back to the 4.2 rear gear, keeping the stock ribcase but going with a lighter flywheel. Street use only but I'm feeling like I've got torque to spare and would like to be quicker... Not faster.

 

[aeronca65t]

Steve:

Yes, lightened somewhat. I took a couple of pounds off the outer edge. I didn't want to take too much and weaken the stock flywheel, but these things are pretty "meaty" so a couple of pounds isn't a problem. By removing from the outer periphery, it has a greater effect. You can definitely feel it.

I have access to a big lathe with 4 jaw independent chuck so I centered it real close but did not balance it.
I keep things under 6500 RPM (OK maybe 7000 using War Emergency Power )