CNC lightweight front spindles

[madjak]

I've started to design up some lightweight front spindles for fun. I figure given I have a CNC machine at home and I do 3D modelling for a living I may as well start making some weird and whacky parts.

Here are my current two designs:

Option 1: This one is designed to be made from multiple billets of ally, waterjet cut to remove the bulk and then finished on a CNC machine. I like this design as I can vary the steering geometry by altering the steering arm without modifying the rest of the part. I'll make the brake mounts interchangeable for different calipers / positioning.


Option 2: Single billet - this one would be cut from a single large billet. Machining time will be astronomical and I loose the flexibility of modifying individual parts. Still a single billet is the strongest lightest option out there.


All of these options are designed around the MR2 Spyder front hub which is a bolt on hub with an integrated speed sensor. The bearings are longer life than a MX5 front hub and since I'm looking at building up a big aero supercharged monster I figured some stronger front hubs would be nice.

[Magpie]

Yes please!

[The American]

I'm impressed with myself when I drill and tap a hole, and then I look at any thread you post! I'm looking forward to seeing this rotrex monster emerge.

[Aiming Faster]

Alloy block on the horizon?

[plohl]

What are your design loads?

Sent from my SM-N9005 using Tapatalk

[OMY005]

Looks interesting, better do some FEA on those fillets on the billet model and the bolted connections of the multi-part ones.

Andrew.

[ricky-pinky]

I am not particularly keen on the bolted design.

Those lower bolts will be carrying the suspension loads in shear, and not only will they be carrying the spring load, they will be carrying the damper compression load as well. While the direction of the load will never reverse, it will still be a cyclic load which I think is not ideal for a shear connection. You would want to make sure it never worked loose.

And as for changing the steering geometry, you will have to remove the lower ball joint every time you want to change the steering arm. I think you would be better off to modify the billet design to accommodate a bolt on steering arm which is independent of the lower ball joint. The forces in the steering arm are low compared with the suspension forces.

[madjak]

Yeah I'm not sure on the bolted design either. Im going to run some FEA on both designs to see how they go before machuning. Both designs need some tweaks before the FEA process though. With design no1 I'm going to strengthen the extrusuon to the top ball joint and also widen the structure across the middle of the hub. I'll also reinforce the lower ball joint with some vertical bracing.

Option 2 I mostly like because I can make it easier. The lower ball joint and steering arm would be held in shear by a recessed interlocking surface that mates to the main hub plate. Even so the bolts will take a fair whack of load so they would need to be high grade ARP bolts of some sort. That joint under heavy braking and turning takes the weight of the car multiplied by the dynamic suspension loading. I'm guessing at around 10 ton of force. If the FEA shows the joints are suitable then I might try it.

For both design I'm thinking of moving to a bolted on brake mount so that I can easily change and tweak the location. This is mostly due to the difficulty of actually measuring my current caliper location to the hub as well as saving a whole stack of machining time. I have some ideas on how to do this and still be ridgid.

[lightyear]

This is a good idea. And if you can run the biggest bearing possible even better.

[greenMachine]

Sooo, we have five studs at the front, and four at the rear ...

I understand the motivation to adopt the MR2 kit, but what are the options for a five stud rear hub? How doable, and at what cost?

I am following with interest, but only because I like this stuff, I doubt I would make the jump.

[madjak]

four stud fronts... the MR2 Spyder hub is the same 4 x 100 as we run currently. I'm not exactly sure how much better the hub bearing is tbh but it's run on the Keisler drop spindle.

[madjak]

[greenMachine]

Thanks for straightening me out on that Madjak, I don't know where I got the idea that the MR2 was five stud . That removes the necessity for replacing the rears, as well as replacing a collection of wheels

[madjak]

Don't worry you are half right! I think it's only the first gen Mr2 and the Spyder that has a 4-stud pattern... all others have a 5-stud.

I think a 5-stud would be better, but yes I don't particularly want to change the wheels. The best bit is you can get the same Timken hub in either a 4 or 5 stud design with the same attachment bolt pattern so you can run whatever your heart desires!

[zossy1]

The Keisler units are very similar to your second proposed design and use the same hub.

I can vouch for them being very, very good. I am now wearing out rear wheel bearings faster than fronts. MR2 hubs are expensive though and will require some funny business for those wanting to keep ABS.

I can warn players though that my experience with the Keislers has been mixed. They required many, many modifications and some lateral thinking to make work. And they make working on the front end a pain in the arse. Only do this if you have reached the end of your front end and steering development path.

If you proceed with this, Rick, my biggest tip is to note that bespoke, aftermarket or custom brake mounting brackets can mount to the inside OR outside of the factory spindle... So make sure your geometry is the same for both options, or you will render aftermarket front brake options as a questionable prospect. Also note tie rod length, the varying ball joint engagement threads as between NA and NB, and the possibility some punters may be using V8 roadsters control arms... Etc etc.