Technical An Argument for Dropped Spindles on Beam Axles

Is there any historic precedent for the use of dropped spindles on beam axles, instead of a dropped axle? If any photographic documentation exists I should surely like to see it.

Dropped spindles seem on the face of it to have advantages from a structural viewpoint. I did some elementary calculations, assuming a vehicle mass of 3000lbs and an acceleration or deceleration of 1g, for normal forces on the kingpins and the resulting torque at the end of the axle:

±29" stock early Ford tyre: 6500lbs top; 8000lbs bottom; 1793lb.ft
±24" hot rod front tyre: 5250lbs top; 6750lbs bottom; 1477lb.ft
±24" tyre with 2½" dropped spindle: 4000lbs top; 5500lbs bottom; 1158lb.ft​

This is equally true for lateral or longitudinal accelerations/decelerations.

Simply reducing the diameter of the front tyre in the examples reduces the torque on the axle by 21% for any given acceleration/deceleration. This torque was never going to lead to axle failures anyway (assuming a good quality forged axle) but elastic strain on the more flexible ends of a heavily dropped axle might be greater than ideal. The more predictable caster and camber can be kept, the better. Substituting dropped spindles on a less severely dropped axle reduces the forces on the kingpin even further (torque 55% less than stock) and allows an axle with stiffer ends.

It's probably splitting hairs unless we go to the taller front wheels a lot of people favour these days. Taller tyres mean higher hubs, and a more extreme amount of drop in the axle for a given ride height. If the tyres are any grippier than stock it might make for a wobbly/whippy front end. Severer dropped spindles would help a lot in these cases.

There might also be advantages to setting up steering e.g. having the tie rod in a more convenient place, though I imagine that scrub radius might be tricky to design around. It might, of course, look all wrong to eyes accustomed to dropped axles: I'm not so sure, hence my keenness to see if it was done before.

 

I need a visual....in my mind it seems like there would be way more"leverage" if the spindle was above the kingpin?
Got a pic or drawing of a dropped spindle?

 

The spindle assembly would obviously have to have a degree of rigidity designed in. My first instinct was also that the leverage happens at the hub, but given a rigid spindle assembly the position of the hub is immaterial. Everything happens at the kingpin.

Or rather, there is more space in the spindle assembly to design rigidity in than in the end of the axle, especially in the fore-aft direction. I don't have any pics, as I've never seen it done.

 

https://www.jalopyjournal.com/forum...-spindles-to-lower-42-48-ford-spindles.95117/

 

Thanks, I'd forgotten about those.

 

See an upside down version on a 4010 john deere. Used to use those rambler bolt on spindles to make dropped trailer axles.

 

Cantilever would be one way to go. This part wouldn't work because the kpi is the wrong way:

And it's huge. The kingpin is 1.5" in diameter. Though a cantilever design would need a heavier kingpin than stock Ford.

Bolt-on spindles are common enough these days, on the back of front-drive cars. It's just a matter of matching up wheel bearings to the desired hubs.

 

Dang Ned, I feel sorry for ya. You must be confined in a very small room due to this Pandemic. I hope you recover soon. The Wizzard

 

You know me. This is how I normally am

 

I'm glad there's always someone else willing to do the Hard part so I can just stay in the Shop and Work.

 

Was just kidding about the John Deere part. Ned Love to meet you someday. Lippy

 

I suspect that the only reason that they don't currently exist is demand, vs. production cost, and that the reason that they did not exist in the past was the difficulty of production, vs. demand/return.

There are lift/lowering spindles for all manner of vehicles now, as the process is better, and cheaper, but we have fallen to a microscopic percentage of demand for such a thing.

Especially so here. These would not be "traditional". Every angry old man would be shouting at you.

 

Matching wheel bearings is very dry research work but it's strangely satisfying. Since the end of WWII a vast array of vehicles from Buicks to Studebakers to BMWs to Ferraris have used the exact same front wheel bearings, i.e. the Timken SET6/SET2 combination. Timken have published very useful information, so I'm using their nomenclature though other manufacturers have their interchange equivalents. The inner bearing (SET6) has a 1¼" bore and an OD of 2.328", and the outer bearing (SET2) has a ¾" bore and an OD of 1.781". By contrast an extremely small number of front-drive vehicles have used these bearings on the rear wheels, and of these none have bolt-on spindles/stub axles.

Moreover, the 1980s, when many manufacturers replaced rear-drive models with front-drive models, also saw the advent of bolt-on sealed, non-rebuildable hub/spindle assemblies. The new pattern is a hub rotating inside a tubular spindle which provides an easy way to mount an ABS sensor. These are of little use here, as the wheel bolt patterns are limited and often don't match common traditional-era bolt patterns, and to my mind their sealed, non-rebuildable nature is contrary to the spirit of traditional-era technology (we won't debate sealed-beam headlights again ) That leaves a narrow window from which to source bolt-on stub-axles.

I've identified three possible sources of bolt-on stub-axles suitable for fabricated spindles, be they for beam axles or any other kind of front end. None use the SET6/SET2 combination but none will need more than one sleeve to fit a SET6/SET2 hub.

1. First and second generation Chrysler Minivan, up to 1995:

The SET16 outer bearing has the same OD as a SET2 bearing, and a SET6 inner bearing can be used on a 0.0637"-thick sleeve.

2. Lots of Audis between 1978 and 2001:

This takes a SET2 outer bearing. A SET6 inner bearing needs a 0.0541"-thick sleeve to fit.

3. Kia Rio, 2001-2005:

This also takes a SET2 outer bearing, and will need a 0.0938"-thick sleeve to fit a SET6 inner bearing. While it is younger, the Kia is however a lighter car than the Chrysler Minivan or the Audis, and so its stub-axles are perhaps better suited to lighter builds.

Early Ford outer wheel bearings have the same bore as a SET2. Early Ford hubs and bearings will fit on the Audi and Kia stub-axles with suitable sleeves inside the inner wheel bearings. Fitting them to the Mopar stub-axles would be a bit more complicated.

Spindle lengths will differ. That information is not so readily available. It might be necessary to make up spacer rings.

I think that might be some useful information right there.

 

maybe build in some camber adjustment?

 

Ned, early Chevy spindles were used on Ts to lower them back in the day. I also seem to remember AMC spindles that were 2 piece being used to adapt disc brakes. Definitely some interesting ideas there.

 

Funny, funny funny,,
There was a new guy who only mentioned that he didn’t want drop spindles for his model A.
Went way off the rails, pissed him off and he got butt hurt.

here’s how to roughly use a ford spindle and amc stub. You can do disc brakes as well.

We can do much better just with a little effort.

Now here’s the Argo manufacturing spindles , an amc copy (almost) for the circle track guys.
very nice high quality forged stuff,



There’s a caliper bracket too, but I left it out because it’s confusing and cheesy.

And here’s the spindle stub, available separately, $37.xx.


It’s designed to take this rotor ( again for the circle track guys) not amc hub.
Who the hell else is going to need an AMC spindle????



That rotor “hub” is Mustang 2.
It’s all there for the tryout. Absolutely use a known good forged spindle.

I used a willwood M2 hub and modified it slightly and used 02 Camaro slip on rotors on the Argo spindles.


I also took 1959 MB 190sl stock spindles and made disc brakes with 1” drop spindles.
The stubs were custom machined. This After we stuffed a big v8 into that little Mercedes. So I’m not afraid to do things that “can’t be done”



Now when dropped spindles go on to any vehicle, it changes the scrub radius.

 

And guess what wheel bearings go onto AMC spindles? SET6/SET2 (except for '75-'78, which take the same SET17/SET16 as the early Chrysler Minivan.) So MGB splined knock-off hubs (for instance) are a direct fit, apart from possible spacers.

 

This whole Idea will really adversely affect the load on the king pins . . . .

 

Not sure on that Ned but you might might do a few quick searches on Rock Auto to check. i say that because once you get it down you can find and compare things pretty fast on there.
I have a buddy who owned a wrecking yard from the 80's up into around 2005 who lowered a number of rigs with the AMC spindles. Pretty much as 31Vicky with a hemi showed in the lead photo of post 16. Pretty damned crude at best and I doubt it would pass many safety inspections. On the other hand. a dropped axle is simple, looks fantastic on most rigs and done right doesn't compromise the integrity of the front suspension. For most it is just the deal of finding someone who can do it right and coming up with the money to pay them to do it.

 

Same here, I can't get a picture in my head of the setup. Bob

 

My analysis suggests the opposite – provided the spindle design maintains the correct scrub radius. The shorter the distance between the kingpin bushes and the road, the better. The position of the hub is immaterial, as any moment between the kingpin and hub partially counteracts the moment between the hub and the road, leaving the moment between the road and the kingpin as the operative resultant.

 

This I can picture on a Sprint Car sliding into a turn and folding the spindles over. Bob

 

Of course the spindles would need to be designed with greater beam strength than stock spindles. In practice I'd expect it to be a matter of some gusseting between the top kingpin boss and the back of the area where the stub axle attaches – clearly lacking in the AMC-early Ford hybrid spindles above.

 

Here's a quick 3D model; no structural calculations or any real detailing done. I used the Audi stub axle because I was able to find dimensions for it.

 

Lacking yes but easily added,
Those things are so cavemanesq rough.
I like the cad version.


The diameters on the spindle are one thing and then the distance between them is another. Both need to be in the right places for suitable hub with correct offset.

 

I got to thinking about this again in response to my speedometer/tachometer thread. The question of where to take speedometer drive from led me to early VW front-wheel speedometer drives, of which I'd been aware but never had cause to have a detailed look at. The ensuing search reawakened vague recollections that other manufacturers had used front-wheel speedometer drives over the years, e.g. @carbking asking about adapting a '70s (?) Oldsmobile setup on another forum (Jon, did you get that sorted out in the end?)

It doesn't make a lot of sense to design an important component around a trivial consideration. But when a lot of trivial considerations all start pointing in the same direction, one more could be enough to make that solution worth looking at. I can't remember the number of times I've managed to improve the design of a building substantially through trying to solve a stupid little problem, which wasn't really all that much of an issue. Time and again, the size of the gain is out of all proportion with the size of the problem.

A front-wheel speedometer drive wouldn't be practical on an early Ford spindle, because the kingpin is in the way. What if it weren't? I was surprised to find that early VWs had physical kingpins, and the way their speedometer drives worked was by the spindle axis not being in the same plane as the kingpin axis. I considered the theoretical possibility of using actual early VW spindles on a hot rod build, but that would entail an Elliot-pattern axle like on a T, rather than the more familiar reverse-Elliot pattern. The spindles also don't offer any useful bearing commonality.

The great advantage of a front-wheel speedometer drive is that it reduces a potential minefield of cumulative driveline shenanigans throwing out the drive ratio to one single factor, i.e. front tyre diameter. The disadvantages are a speedometer cable flopping around as the front wheels steer, and the fact that you'd still need some kind of corrective gearbox to bring the turns-per-mile to what your speedometer needs. If you've got a quickchange or an oddball overdrive, it's worth exploring. If you've got a quickchange and an oddball overdrive, it's definitely worth exploring.

On a dropped spindle of the kind I'm contemplating here, there might just be enough room to drive a speedometer cable over the top end of the kingpin, without materially changing anything else in the design. But then, it becomes obvious that it opens the possibility of moving the spindle axis off the plane of the kingpin axis. Would there be any advantage in that?

The rule-of-thumb of a baseline 7° of caster, and then experiment from there, makes sense as regards the kingpin inclination on most early Ford axles being around 8°, so that positive camber gain in steering due to KPI gets largely offset by negative camber gain due to the caster angle. And for most purposes, the resulting ±1½" of trail is reasonable. There might be advantages in increasing the caster angle, but at the price of increasing the trail at the same time. At 12° of caster the trail might be almost 3". The problem with that, if I understand it right, is that it reduces the proportion of total trail any change in pneumatic trail represents, making it hard to feel what the front tyres are doing. If anything we might want to reduce trail below the stock value.

For the same amount of effort it would take to fabricate dropped spindles with the spindle axis coplanar with the kingpin axis, the spindles can be made with the spindle axis about 1½" ahead of the kingpin axis. They'd obviously be handed. That kind of geometry might have serious dynamic benefits, and thinking-wise it all comes from a silly little thing like a speedometer cable.

 

Looks "Hokey"on all but full fender cars, much to visible on highboy/open wheel variety.

 

Depends on how it's designed, surely? Or will any spindle other than a '37-'41 Ford spindle, even one of the same era, look wrong?

 

Good Morning Ned. I just did a quick read over to catch up with what you're accomplishing (this quest started in 2020). Sounds like your Doctors still have you on the same medications, I guess that's good. Sure hope at some point you can put all your research to bed and get in the Shop and actually build something that makes you satisfied. I would enjoy seeing some end results. I do understand not being like all those other guys that just put things together and move on. Like 3 of my X wives have asked, "why can't you just be normal" and I always thought I was.

 

I think Pete covered it succinctly. All forces seen by the spindle are centered in the kingpin flanges of the axle. Moving the spindle up or down is going to add offset leverage. The components (spindle and kingpin flanges on axle) can be enlarged and strengthened to handle this, but the original design is economical in material and has the least offset forces leading to less wear.
As for the Speedo drive, look at Baja. They ended up drilling, tapping and threading an insert for strength on the LF spindle. You could gear a speedo from something like an ABS ring on the hub to a cable if you had to stay mechanical. The electrical design has already been optimized for direct reading, and GPS has rendered direct readings obsolete.
Heck, you could add a toothed gear to the outside rim of a spoked wheel and use a bicycle generator hollowed out to accept a cable if you wanted to go full steam punk.