I've never seen a hot rod with a DeDion axle, though it seems a natural. To those who are unfamiliar with the set-up, it's a solid axle that connects the rear wheels but doesn't incorporate the rearend. The rearend is an IRS-type unit bolted to the frame, with jointed half-shafts. The axle can be sprung by whatever means, located by whatever means, have brakes on its ends or inboard on the rearend unit. The advantages are lower unsprung mass, constant camber, and no torque reaction. And, it was the system of choice on exotic racing stuff from the '30s to the '50s. One would have thought that at least some hot-rodders knew about them, and that at least one tried it. Does anyone know about the use of a DeDion axle on a hot rod, either back in the day or since?
Good question Ned, Welcome to the HAMB. I remember seeing one in a Hot Rod featured car from the 1950's or 1960's. Harry Miller used one in his Front Drive cars, and every Cord used one.
Thanks 37. Now that I think of it I seem to recall an Alfa-Romeo-powered '29 RPU somewhere in the Antipodes, that has the Alfa transaxle and DeDion in it. I don't remember seeing what the installation looked like, though. I know about the Cord L-29. If memory serves it even had the front bumper mounted to the axle.
Ned, What is the story on your avitar? Whatever that is it has a really appealing look to me, Bentley, Jag and Mercedes in the 1930's had that look, long hood compact body just looks so right to me.
not sure most de-dion axles could handle the torque produced by a healthy small block ford, mopar, or chevy. Maybe some of the flathead powered roadsters and the 4 and 6 cylinder jobs could do it but you would have to make it beefier. The other issue is that de-dion is a type not a brand so there are many different executions of the same concept and none of it seems as cheap and easy as installing a solid axle 9-inch, 8.8 inch, 12 bolt, 10 bolt.....etc.... Also the cars that used them are not exactly the rarest and the cheapest. Have you seen what Alfa/Lancia/Aston Martin parts go for these days? The only exception I can see is the 1991-1994 Chrysler AWD caravan which used a de-dion axle arrangement. Yes it will look slightly modern so you will have to dress it up a bit and let's be honest - when was the last time you saw one in a salvage yard?(they didn't make that many compared to front drive caravans). But if you can score one I doubt it will be like paying for an Lancia rea axle. Here is a DeDion that ford used in the EV ranger. As far as I know all these trucks have been recalled by ford years ago but you can use the photo for how to rig up your own. This used an insufficient carbon fibre leaf spring and a watts linkage.
I would guess that some one here in the UK will have used a DeDion, Pretty sure Rover P6 used that style rear, chances are some one will have thought to use the V8 trans and axle from the same donar. Don't see any problem as far as power given a suitable pumpkin, Advantages over Hotchkiss outway any down sides, However as complex as full IRS (possibly more), so probably if you are looking for something which works better than the Hotchkiss ( a list which includes every other design one could think of ! ) I would be tempted to go with a full IRS, the camber thing is over rated, grip does not change that much with increasing negative, and the angles only change by a couple of degrees at most.
I think you're mistaken about the torque thing. All torque reaction, be it around the drive shaft or around the axle half-shaft axis, is handled by the final-drive unit's mounting to the frame. The strength of the DeDion axle doesn't enter into it. And there are lots of diff units to choose from. The Jag and earlier 'Vette units are obvious choices, but there are others, from Mercedes/BMW/Lexus/etc. through Ford Sierra(Merkur)/Toyota/etc.; and aftermarket 9"-based units and independent QC units at the other end. The Locost guys are going in for fabricated DeDion axles in a big way. I've seen a number of designs. In fact I had an axle made up for the Morris about ten years ago, but all kinds of stuff happened in my life that caused the car to go into storage for ten years before I had the chance to install it. And, story of my life, the design has moved on since then! I'll have to do it all over again to the new spec. The simplest, I suppose, would be to get hold of a semi-trailing arm IRS, just the subframe, arms, and hubs, from something like an '80s Mercedes. Make up a jig to keep the camber and toe correct, weld on some heavy angle to hold the arms together, remove the subframe, and then cut the arms off such as to allow a 3" straight axle tube to be welded to them. Cut off the angle, add attachment points for springs and links, and there you go. I'll probably go that route with the Morris.
Thanks Weasel. An old girlfriend of mine had an early Alfetta that sometimes ran. My cousin had a GTV 3-litre that ran very well indeed. If I remember correctly, there are a couple of weak points to that transaxle. The second-gear synchro hub is made of a special sort of durum pasta that Alfa-Romeo developed for the purpose. The pinion strips if it sees much over 500bhp, and the prop-shaft bearing on the front of the clutch housing has been known to break off under power. Nevertheless, these 'boxes have been used behind V8s in the 450bhp region, presumably with care. And I remember, the Watts linkage imparts a characteristic waggle.
I'm helping a friend finish up his 59 Devin SS and it has the DeDion rear end. The finned aluminum center housing uses a 55-64 Chevy dropout pumpkin so it will take a little abuse. Bill Devin used these in his small block Chevy powered SS models and possibly others too. It's a very cool looking rear and supposedly works well. Max
technically you are right in that the dedion really only refers to the tube axle and not the diff itself and I really meant that the pumpkin and gears would not be up to the forces generated by most domestic v-8s having been designed for use behind smaller less powerful engines. the GTV setup is strong enough but pricey.
Juan Manuel Fangio ( The Grand Prix Champion ), built a couple of Race Cars that he Raced in his Homecountry ( Before he went on to Maserati's, etc ) At least one of those ( maybe all ), had a home built De Dion setup.
That Alfa thing looks more like an IRS than a DeDion from here. Anyway, my roadster is not DeDion but swing axle which was popularized at Bonneville by the Kenze and Leslie team as well as the Markly Bros and Bob Herda. Like any self respecting Hot Rod DeDion rear end it makes use of an American center section. In my case a V8 quick change. Lincoln touque tube bells and '%4 Olds outer axle housings, halfshafts and brakes. This also allowes the pinion gear to be solidly mounted to the frame and keeps the short drive shaft angles correct dispite suspension travel. I think the DeDion might be better.
Perfectly fine rear end to use, stop there ! Can't see any advantage in making an IRS into a DeDion, It's a backward step, sorry if I am missing the point, I can see wanting to get away from a solid axle, all the arguements for unsprung mass, and better wheel location etc work fine for me, the DeDion design is better than Hotchkiss every day of the week, but against IRS it's still the poor brother, the unsprung mass of an IRS set up will be even less than DeDion, so the very thing that makes the DeDion desirable is better in the IRS you are going to cut up. Or at least that's how I am seeing it at the moment.
And I have a Alfa Romeo Alfetta rear axle to maybe use in a future project. Its laying on this pile, upside down... I wouldnt be scared to send more than 300Hp through it. It doesnt take up any of the Braking Load or Engine Torque, and the Alfa isnt that light of a car ( compared to a Hot Rod ) I think that would look awesome with a Quickchange centersection with inboard aluminum Buick drums. I built a little racer of my own with a De Dion in it as well, years ago. ( it was acctually a fabricated cage that wrapped around the Engine/Gearbox, but the geometry was the same...) I really believe in De Dion rear suspension. It has a lot of the advantages friom a IRS and a lot of advantages from a live rear. Its almost the best of both wolds. Ferrari experimented with a De Dion on their Formula 1 cars as late as 1978... ( they were very capable of building a good IRS, by then ) I read somewhere that the drivers loved it. The car was nice and predictable in its handling. But the stopwatch said it wasn't any faster than the IRS, so the project got canned.
Damn Alex! Thats unlike anything I´ve ever seen. Is unsprung weight a problem with this type of set up? The Rover P6 did indeed have a De Dion axle. What I haven´t seen mentioned is the need to allow for the arc of travel of the axles. Rover overcame this by the use of a sliding joint in the De Dion "tube" axle. Otherwise you need sliding CV joints of some description. The Jag and Vette axles are not De Dion axles as far as I understand the term.
No, it was very light... It was a Spaceframe ( kinda like a '60s Singleseater Chassis ) that I made lots of scale wire models for to see what was possible, Lightness/Strength/Space wise. I built it out of thinwall mild steel tubing, that I Riveted and Bonded ( with the same type of glue that they use in the Aircraft Industry ) Aluminum panels to. The Wheels were very light 3Pc Compomotive, the bearings & hubs were off a small FWD Fiat, and I adapted the brake drums off an early ( '50s ) Fiat 600 off which I cut most of the Backing plates away. ( the car was light, and it was a Parkinglot Racer, so it didn't need much brakes ) Those Fiat Brakes were sort of like Miniature Buick Aluminum Drums... 2 more pics. I'd have to look it up to be sure, but I think the 2H Chaparral had a De Dion as well..
Semi-trailing arms? Are you serious? Sure, they're better than a live axle, in terms of the expected performance envelope of a European high-performance sedan. But once you go outside that you've got both camber and toe issues to contend with. Semi-trailing arms are as much about space under the back seat as handling. That's why most of the much-vaunted multi-link systems are little more than semi-trailing arms with a bit of additional articulation and extra control links to iron out the worst misbehaviour. What I've found with all kinds of independent suspension is that fine-tuning for one aspect very often makes a mess of other aspects. Get everything right in side elevation and it no longer works in cross-section, and vice versa. Get everything right in bump and it no longer works in roll and/or pitch, etc. The beauty of a DeDion is that you can set it up in cross-section like you're going road-racing, and in side elevation almost like you're going drag racing. I say almost because it's not quite the same as a live axle. Because there's no torque reaction in the axle you're working with the line from the rear hub to the CG, not the contact patch to the CG. So, it's not only that you can emulate a live axle, you can emulate a live axle set up to launch hard. I can't see that done with an IRS without screwing up the behaviour in roll completely. Brilliant stuff, Metalshapes! I'd love a look underneath one of Fangio's Chevies. But I'm almost certain you're going to have clearance issues using an Alfetta axle with a QC. Even on the stock set-up the side shafts trail back about an inch from the diff. Increasing that to account for another 8" or so of diff unit will push the CVs to extreme angles. I like the idea of inboard Buick drums, QC, and DeDion, though.
37, that, believe it or not, is a '27 T. Here's the complete sketch: It was indeed inspired by late-Vintage European performance cars. The fenders are reworked repro Deuce items, and the repro T shell has a fabricated lower part to make the proportions more vertical. The thing that makes the look is the backward slope of the frame, which is extended at the back, with a kink under the rear axle. That's more typical of lighter cars like MG, Riley, Frazer-Nash, or early Aston-Martin. This was actually part of the '31 A project's design development. Every so often it pays to do a radical re-think and ask yourself if things aren't getting out of hand: so I recast the project as a '27 T, with the firewall in the stock position (you can see the line about ⅔ of the way along the hood) and an 1800 VW banger like the one in my DD. The wheelbase stretch is no more than relocating the front axle parts. But I've since come into some good '31 parts, so it looks like the project wants to be a Model A. But not before gaining a lot of input out of the '27 T exercise.
Oddly enough yes, As I said earlier the camber thing is too easy to get hung up on, grip does not decrease suddenly with increased angles of negative, The arm provides a very strong direct path to resolve thrust of extreme traction forces, without having to be masively heavy. In the UK same time as we had Rovers on DeDion we also had Michelotti Triumph Big Saloons on Semi Trailing, both were way better than any solid axle, but there was not that much to choose between the two, if anything on loose stuff the Triumph seemed to find more grip. For a hot rod I would think the even lower unsprung mass of a semi-trailing would be an advantage over DeDion, which is unlikely to be over-ruled by minor camber and toe changes, which don't effect grip as much as pure 'keeping the tyre pressing the black top' does. Don't get me wrong I would be the first to admit that it's not perfect, but then if I were going to the trouble of modifying parts to make a 'better' design why stop at a DeDion ? Probably easier to go for a Broadley Lola/GT40 'eight bar', would look traditional hot rod from the side with its long parallel links, and works far better than DeDion.
Yeah, that wouldn't fit. But I'd cut and move the tube untill it does. ( moving the axle back from the Diff centerline would increase driveline losses because of the extra angle in the CV Joints ) I would want to have that all in line... I acctually used one of these Alfetta DeDion axles to build a stronger rear suspension setup for a Racing Abarth 1000TC ( the stubaxles are known to break on those, and some have crashed because of that...) That was a IRS that worked off the original Fiat pick up points. Another thing that I would do different than the stock Alfa DeDion setup is the single foreward mounting point. My Blue Racer had that too and with the tinyest play on the sideways location that gives kind of a skidsteer effect on the handeling. ( great for a super a agressive turn-in, but not too nice at speed ) It was more noticeble on that car because the wheelbase was so short...
I've always liked the look of those Triumphs, especially with the early front-end treatment. You still see them sporadically: (at the risk of getting a bit OT)
Yeah I owned a few of them, Last one with triple webers, cam, flat top pistons, gas flowed etc was a real beast, biggest problem was not the rear end ( poly bushed ), but the huge mass of the iron block in line six which made the car under steer like a pig what ever one did to the rest of the car. The car long since died of terminal rust, but I saved the rear end to build a hot rod, The cast aluminum arms are hollow, one finger light, while far stronger than was ever needed. I have made a few home brew tubular semi-trailing rear ends, using hubs from FWD donars for small light vehicles, Played arround with pivot centres on Cad for a bit, seems to always work well enough, And for a light vehicle where the unsprung mass thing is problem, I actually think it has great merit.
Thunderace, have you ever considered semi-leading arms? It just struck me last night that that would create a situation where the weight transfer on launch tends to self-correct to the optimum. That is, the "leading" geometric component would tend to align to a line through the CG and rear wheel hub under power. That's opposite to a (semi-)trailing arm, which will tend to increase whatever deviation there is from the optimum as soon as there is a forward tractive force on it. The DeDion set-up I'm thinking of for the Morris is a bit of an elaboration on the principle, in that the axle pivots on an axis near the axle tube. That way the mass of the tube itself is pretty much sprung (it rotates about the heavier bit) and the unsprung-mass situation is that of a semi-trailing arm system.
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