Strange Days Bellytank 10-7-07 Does this make my rear end look skinny?

We measured and re-measured, but no matter how we looked at it, only 3 1/2 inches of axle tube will stick out of the center section on each end.

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Phil, our machinist, made some stubby axle tubes for the Cherokee steering knuckles that just slid inside the quickchange tubes. We set the center section in the car to hold the axle in position.

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Then we inseted the knuckles into the tube and set the caster at five degrees.

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Once everything was in position we welded it in place

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Here's a picture of the front wheel drive axle in place on the bellytank.

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To get this thing to handle, we're gonna need a pretty heavy offset on our wheels to get the scrub radius correct. Who makes offset wheels for land speed racing applications?

If you are interested in the whole build, you can find it here in diary form:
http://kaparich.homestead.com/Bellytank.html

 

toronado or eldorado wheels may work.

 

In laymans terms, If you can imagine a king pin going through the balljoints, and follow that line to the ground, It should meet the ground at the center of the tire.

From the book :
Scrub radius is the distance between where the Steering Axis inclination intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Different wheels or tires from side to side will cause differences in scrub radius as well as a tire that is low on air. Positive scrub radius is when the tire contact patch is outside of the SAI pivot, while negative scrub radius is when the contact patch is inboard of the SAI pivot (front wheel drive vehicles usually have negative scrub radius).

If the brake on one front wheel is not working, with positive scrub radius, stepping on the brake will cause the steering wheel to try to rip out of your hand. Negative scrub radius will minimize that effect.

 

You will not be running on road courses anyway, I hope. If Jeeps can live with that set-up, I would think tanks can.

 

Chaz,

Looks like a ton of head scratching went into that drive set up. any idea how many others have run a similar set-up?

s.

 

As far as we know, no one has done it this way, there are some front wheel drive streamliners but no tanks we are aware of. Mostly we go by what we think might work. Four old heads to scratch seem to be better than one on this project so far.

 

By the looks of the top of my head, I've been scratching too much!

 

Hotrodding at its best! Thanks for the update, your build is a topic of conversation that crops up (over cold beers) here in Billings about once a month.

s.

 

At Bonneville last week I woke up in the middle of the night thinking about scrub radius. Must be something in the water. Wayno

 

How is the drag link going to work with the pumpkin in the way? Just thinking out loud?

 

And the tie rod?

 

It looks a bit worse in the pic than it actually is. Right now we're looking for a small manual rack and pinion unit that can sit atop the change gear section of the pumpkin [which is lower than the ring and pinion section of the pumpkin.] the rods will angle some downhill to the spindles .

 

MRT should be able to make you wheels.

 

Sorry I couldn't help it...

 

Keep on!

 

I don't know about the paint scheme. Seems a bit played out. But I love the car!!

 

FWIW- M/T had a similar setup on his twin motor dragster, using a Jag r&p.

 

What size tires will the tank be running?

 

Tires should be 26" OD. Probably Goodyear frontrunners.........

That jag rack & pinion looks like just what we're after... Thank you!!
Now I gotta find a wrecked Jaguar in .... Montana.. Why couldnt it be offa some goddam beater pickup truck.? They're all over.
Mickey Thompson was a god.........

 

I've got a question, and please excuse me if it's been asked and answered earlier, but how are you dealing with the reversed rotation of the rear end gear set?

I know that 9" Ford gears don't deal well with being heavily loaded in reverse, something to do with the different face angles on the load and coast side of the gears. I'm fairly certain that QC R&P's are of a similar design, how did you get around this fact when designing your drive train? Does someone make an R&P set that's designed for reverse rotation?

I've also been wondering about your transmission and all that, are you just running it in reverse and using it as a single speed, or what? I guess you could make the motor a counter rotator and then use all the forward gears, but the whole train would be spinning backwards, which brings up the inverted pressure angles again. Just wondering how you guys got around that problem.

OK, I lied, it was about forty questions. What can I say, I'm an engineer, so solving problems by using things in a manner other than was originally intended is pretty much what I live to do.

BTW, that is very nice cage work. You still gotta have balls to strap that thing on, but at least you've given yourself a better than even chance of unstrapping and walking away at the end of the run. Keep up the good work, and keep taking the pictures, it's like mechanical ****ography.

 

Hey Coolhand. Thanks for the questions. Thats why we post here. Ive learned more from these postings than Info I give out for sure. [That jag rack and pinion was the learning experience this week]
The gears in the rear end are reverse rotation. We got the setup from Joe Timney at Delaware Ch***is Works. He was like an encyclopedia on these things as well as a dealer AND a land speed racer. That saved us from having to run the engine crankshaft in the opposite direction.
The other option was to run the rear end upside down, but we thought it might not oil properly. Its really been a lot of fun researching what's out there.

 

So the carrier is oriented 180 deg from normal then, or the gears are just meant to run backwards?

If you're just running the drive shaft counterclockwise (when looking at the drive yoke on the center section), what's going on in the ******?

If the fix was as simple and elegant as just flipping the carrier with a purpose built R&P set, I've got to say that I've found one more thing to love about QC centers. Did you have to do any machine work inside the center section, or did it all just drop right in?

 

"reverse rotation" (not 100% accurate term by the way) means they are cut to operate in the opposite direction. Generally they are gears for 4x4 front axles.

The engine and ****** will operate as normal.

 

Thank you tjm73 I think you are exactly right. The gears are meant to run backwards.That would explain why only the lower ratios were available.

 

OK, I still don't get it.

I'm not trying to be dense here, and this certainly isn't my first rodeo when speaking of gear trains, but I am failing to see how you can make the axles spin clockwise (when looking at the right hand axle while facing the yoke) in a quick change rear while the yoke also rotates clockwise (when facing the yoke), by changing nothing but the ring and pinion set.

I mean, I know they're helical gears, but it's not a worm drive set, the two meshed gears must still spin in opposite directions. Turn the yoke clockwise while facing it, and the right hand axle will turn counterclockwise, and vice versa.

The only way that relationship could change is if the ring gear were facing the other side of the center. Meaning that while facing the yoke, the teeth on the ring gear face the right bell instead of the left bell like normal.

Most 4WD transfer cases I have seen use a chain type setup inside so that the front drive shaft spins counterclockwise if you're facing the yoke. Either that, or they use an opposing gear setup and have the ring gear on the opposite side of the pinion as the rear gears.

As you can see, I'm somewhat befuddled here, please lay out the whole setup in plain terms, so I can see what you've done here.

It seems like it ought to be simple enough to just open up the other side of the pinion support, and load the spool and ring gear into the center from the left side instead of the right (so that the teeth point to the right when facing the yoke). So long as your gears were cut to mesh in that configuration, I don't see why that wouldn't work. Is that essentially what you've had to do here, or have I totally missed it (again!?!)?

 

I'm having difficulty explaining it. It's not just the gears that are cut in an equal/opposite pattern but the housing is set up 180 degrees as well.

Cutting the gears in the 'reverse rotation' makes them stronger than running them 'regular rotation'. You get a better, stronger contact pattern. They don't actually run in reverse, but they are setup in the revers fashion.

 

Gotcha.

That's exactly what I was thinking you'd have to do.

Looking at a Winters Sprint center cutaway, I think a guy could do this by opening up (milling a slot to expose the pinion on) the left side of the pinion support, turning the carrier end for end, and possibly swapping the bells side for side. You'd still need a purpose built ring and pinion set though.

Makes me feel a little better to know I wasn't imagining the difficulties here, I was beginning to think I had lost all my mechanical mojo.

EDIT: Another question for the OP has just popped into my head. Is there any reason in particular that you chose to do a rear ****pit with front wheel drive instead of a front ****pit with rear wheel drive? The front drive car looks cooler, but the rear drive car seems like it would have been loads easier to build.

 

Pulling the car from the front eliminates the chance of the rear of the car trying to switch ends with the front of the car at high speed if you loose traction.

ie...FWD cars rarely spin out. Where ever you point the front wheels, the car tries to go. RWD is more fun in my opinion, but FWD is more stable in poor traction situations. AWD is most stable, but you use a lot of power turning all those parts.

I may be wrong but I think these guys are doing it to prove it can be done and maybe a bit of "just becasue".

 

That makes sense, though I would think you could stabilize a RWD car with aerodynamic acoutremonts (wings, fins, vertical stabilizers, etc much the same way you keep a jet aeroplane oriented correctly in flight). Perhaps such is against the rules, I'm not really that familiar with racing of this sort. I'm an oval track racer myself, but this stuff is still supremely interesting to me.

You gotta respect design decisions based on "because I want to do it that way". That's the manner in which about 80% of my ch***is design decisions are made as well.

 

Basicly we are doing it this way just because,and we are trying to make it as safe as we can, We really are not trying to break any records, just 4 old guys who want to break into the 200mph club and have fun along the way.