Ace-Garageguy

The June 1963 Hot Rod Magazine has a full writeup on the "rollerskate" car (the June '63 Road & Track has a comparison of Thompson's rollerskate and the Lotus 29 as well). August '62 Hot Rod has details of the more conventional looking Thompson/Harvey first-generation mid-engined car. There were developments over several years, and it can all get a little confusing...and there's no shortage of just flat wrong information floating around too...as usual. The elliptical cross section was only the skin. The chassis was a relatively conventional tubular spaceframe, built of .050"-wall titanium tube.

Having the shafts slightly offset, as referenced above, only serves to keep the joints "working", and lubricated. Obviously, as the suspension moves around (when the car negotiates a bump, for example), the offset angles will become more severe during the up and down movement of the vehicle. If the bearings in the joints have run dry because the shaft is too straight most of the time, they may not be able to cope effectively with the increased loads caused by greater offset angles, and early joint failure may result. Three things are usually responsible for driveshaft vibration. 1) By far the most common in hot-rods or engine / trans swaps is a failure to match the pinion angle to the angle of the crank / trans centerline. That's one reason why the articles and illustrations you found make such a big deal about it. As noted in my first response, the angular velocities of shaft elements are different on either side of each joint at various degrees of shaft rotation. A properly set-up shaft, with the angles of the pinion and crank centerlines matched closely (with the vehicle at its normal going-down-the-road ride height) will cancel out these variations and both ends of the shaft will have the same instantaneous angular velocities at any given time. Mismatched pinion / crank centerline angles will have both ends of the shaft fighting each other as their angular velocities change at slightly different rates. Depending on the design of the rear suspension and the compliance of engine and drivetrain mounts, this may be felt as a vibration at certain road-speeds or loads. It will certainly hasten UJ failure. NOTE: Not all rear suspension designs are equal when it comes to maintaining pinion angle under all conditions. Consider a live rear axle on coil springs, controlled by trailing arms. In this design, the rear axle will move in a slight arc as it moves through its bump / rebound travel, and will rotate around its centerline. The pinion angle will change during this movement. 2) Another leading cause of driveline vibration in non-OEM installations is having the universal joints slightly "out of phase". This happens when an inexperienced or sloppy driveshaft builder fails to align the crosses of the UJs EXACTLY, for instance, where a shaft has been shortened or lengthened, or a yoke on one end of the shaft has been changed to accommodate a different trans or rear end. This will usually manifest itself in a moderate to severe vibration at all road-speeds. Competent driveshaft shops almost always get this right. Guys who shorten or otherwise modify their own shafts rarely do. NOTE: It IS possible to do a fine job of modifying a shaft in the garage or home shop, even without a lathe. But it takes an amount of CARE and THOUGHT that is usually lacking among amateurs, and a lot of "professionals". 3) The third cause of driveshaft vibration is simply out-of-balance. Driveshafts need to be balanced, just like any other rapidly rotating component, and they usually have small weights welded to them to accomplish this. When a shaft is modified, it needs to be re-balanced by a competent shop. An out-of-balance shaft will often be felt as a cyclic vibration at some vehicle speeds, not others. Getting hot-rods and customs to behave like OEM vehicles can be time consuming and frustrating, particularly when the original builder(s) failed to take things like these seriously. NOTE: On a pure drag-racing car as shown in the opening photo, having the driveshaft running almost or dead straight is really OK. The car isn't going to be run for miles and miles on end with the UJs not "working", so with an occasional shot of grease, the joints will be just fine...but the crank / trans centerline angle and the pinion-shaft centerline angle still need to match exactly.

This is one of those instances where insufficient knowledge and experience can lead to incorrect assumptions and interpretations. The diagram you found is CORRECT the way it labels "wrong" and "right". If you look closely, you'll read that the centerlines of the pinion shaft and the crank centerline are parallel, which I noted is necessary in my comment above in NOTE 2. You will also notice that they are not excessively offset, which I referred to in this part of my response: "With universal joints operating at higher angles etc." The car and engine in your photo in the opening post are both excessively jacked up, and to approach the relatively minor offsets of the shaft elements in your last illustration, the engine needs to be angled as shown. I assure you, if you were to draw this all out to scale, you can get the relatively minor shaft offsets necessary for correct universal joint operation with the engine at that apparent angle. HOWEVER...not ALL car builders appreciate all the subtleties of pinion-angle and driveshaft setup, and some pretty spectacular results have been known to occur, like when the front UJ snaps and the car pole-vaults on the driveshaft.

Nobody has actually answered the question. So I will. You are correct in your assumption that the significant tail-down angle is to eliminate much of the "drive shaft angle" that would occur if the engine was mounted level. NOTE: The engine IS raised to enhance weight transfer, but the ANGLE the engine is installed at (within reasonable limits) has very little effect on where the center of mass of the engine / gearbox assembly is located, and that is the important issue relative to HEIGHT. As far as the drive-shaft angle goes, it has to do with the motion of the elements of the universal joints, and the torque transferred through them. In theory, there is no horse power loss due to angle. In practice, universal joints do not do well at any but the smallest angles (which is why CV joints are used in higher angle applications). With universal joints operating at higher angles, the angular velocity of the output shaft (the element of the driveshaft behind each universal joint in this context) is varying above and below the angular velocity of the input shaft (the element of the driveshaft forward of each universal joint in this context). What that really means is that the output velocity and torque vary in opposition, cancelling any variation in horsepower.... BUT...the varying loads on the crosses, cups, bearing rollers, etc. tend to make them explode once the angles become large enough. NOTE 2: The nose of the differential pinion shaft also needs to be corrected for everything to work right. The angles that both universal joints are working through need to be essentially equal. This requires rotating the rear axle assembly so that the angle of a line drawn through the center of the pinion shaft (relative to the horizontal) matches the angle of a line drawn through the crankshaft and gearbox output shaft. Anyone interested in the math? Here you go... https://en.wikipedia.org/wiki/Universal_joint

Anybody got any pix?

I love this thing, but the main reason is that you USE it. We've seen the shots of her in the never-never. What I have no use for is the urban cowboys who never get dust on the Armor All on the tires. Same reason I have no use for the guys in Porsches and Ferraris cruising around in first or second gear. Take the damm thing to a track day, or a slalom, or up the winding mountain-back-roads...fine...that's what it's for. But most of the ones I know live in air-conditioned luxury and rarely get driven over 50 MPH. if they get driven at all. Somehow, I don't think those are happy machines. Life's too full of opportunity to do real stuff to settle for being a poseur.

It's been warm and wet for days now here...just warm enough to let the mold and mildew get a head start on Spring. Living in this part of the Southeast is like camping in a festering swamp. Rust and fungus. And people who seem to need to live right up each other's backsides. None of which I'll miss when I move West.

Mickey Thompson was one of my heroes when I was a kid, and I owe a lot to the inspiration he provided. I've got 2 models of the early version of the Challenger I in progress (build thread here): I'm doing a few of his other cars as well, but the one that's been most elusive is his '62 A/FX Pontiac Tempest. I finally snagged enough stuff to get going on this build, with enough leftovers to do another one...

Anybody remember "I'm not a doctor, but I play one on TV"?

Oh boy. If you DON'T respond to comments, people call you a stuck-up snob. If you DO, you're an attention hound. You just can't win around this place. Merry New Jeer.

I dunno...I guess you have to hand it to somebody who can actually get paid for...whatever it is. At least you won't be supporting her while she's living in Sfan's neighborhood, slinging soy shakes for $5 per hour.

At least, sir. At LEAST.

Hey...I finished TWICE as many this year as I did last year, and 5 TIMES as many as the year before.

English Lit isn't a bad major for someone who really wants to write professionally, and a Fine Arts or Art History degree is useful for someone who wants to paint or sculpt (but you'll probably be paying the rent as a waiter or bartender or dog-walker until you make it). Admittedly, people actually making a living with these degrees doing much other than teaching are pretty rare on the ground, but knowing background makes for a superior technician, no matter what the field...including the arts. What I can't figure is how somebody pursuing a degree in subjects like Gender Studies, Comparative Religions, or Theater Arts expects to find a paying job that uses anything they've "studied".

I didn't mean to be offensive. HONEST. PRESENTS and PRESENCE are two entirely different words with different meanings, not a "spelling" error. People routinely use SILICONE and SILICON interchangeably too, even though they're not. Then there's THERE, THEIR, and THEY'RE, which get misused continually here and all over the web...even by "professional" writers. TO, TOO, and TWO. And WHOSE and WHO'S. And ITS and IT'S. Ad infinitum. Anyone see ME make a mistake in word usage, or technical information, or ANYTHING...PLEASE FEEL FREE TO POINT IT OUT. I'd rather be corrected than to continue thinking wrong is right....or miss something I should have caught while editing.

This particular nothing is in 1/8 scale (which is probably why it photographs more like a 1:1 than most of my work), but it's based on a 1/25 scale nothing I did as a design study some time back.

I kinda like that. At least all the parts look like they go to the same truck.

I'd buy this. I'd even sell off a couple of other vehicles to do it. Put a little shorter rubber on it, I'd be a happy guy. And it looks like it wouldn't mind getting all muddy.

Maybe you meant "presence"? One more time, this thread was NOT directed specifically at millennials, but only at stupid in general. I'm an old fossil, and my acquaintances include many more "stupid" than "smart" individuals. Frankly, I'm surprised "civilization" has endured as long as it has, with the majority of those running it being securely within the "average" sector. Then again, it's not at all hard to understand why things like the "energy problem" weren't sorted decades ago. The tech has been there, but stupid just looks the other way.

I think a lot of it is compensating for a lack of inches in other areas.

In all honesty and fairness, I actually LIKE the overall shape, major lines, and proportions of the new Chevy. What puts me off is the absolutely unnecessary complication of the detail design, and the tortured sheetmetal where the front fender blends into the door. The grille / front bumper styling is just too complex, period. It's like every member of the team was allowed to make a mark on the drawing, and nobody ever bothered to actually integrate them into something coherent. And the character line that droops under the mirror, fades out, and then magically reappears farther back on the truck looks like crapp. Raise the mirror a tick, and continue the line all the way down the side of the vehicle. OR, remove the upper crease from the front door, and bring the character line back on the rear door, echoing in reverse the front fender treatment.

The sad truth is that many folks who identify themselves as "patriotic Americans" can't tell you where the Vietnam war was fought...or when...or who America's allies and enemies were in WW II. There are a lot of vocal young people proclaiming their adherence to the tenets of various philosophies that are the antithesis of what America has always stood for, but when pressed, they know absolutely nothing about the systems and ideologies they claim to favor. This statement may be seen as veering too close to "politics", but it's as far as I'm going to go. Widespread ignorance endangers freedom more than any other single factor...other than apathy, which is itself often the product of ignorance.