maschinenbau
maschinenbau UltraDork
2/7/22 8:57 a.m.

In reply to Mr_Asa :

It's just to center the rotor on the hub until the wheel is tightened. The lug studs get it pretty close, but the plastic centering ring removes the slack and holds the rotor snug so it doesn't fall off while fitting a wheel. It shouldn't actually bear any load since the clamping and friction force of the wheel does all the work.

But I'm happy to accept free parts! 73.5mm OD x  62.5mm ID x 5 mm thick

Mr_Asa
Mr_Asa PowerDork
2/7/22 9:28 a.m.

In reply to maschinenbau :

I'll dig around tonight and see what I have.  No chamfer or anything weird needed?

maschinenbau
maschinenbau UltraDork
2/7/22 9:38 a.m.

In reply to Mr_Asa :

A small chamfer or break on the edges would be nice, but nothing specific needed

maschinenbau
maschinenbau UltraDork
2/20/22 7:08 p.m.

The McPherson-wishbone conversion bracket is finally complete! I also added sway bar link mounts, keeping the stock Toyota sway bar and hardware.

Probably the single most important part on this entire car, so I took my time. Lots of measuring, fitment, weld prep, beveling, and really careful welding. This car will have a heavy rear weight bias, so lots of load going through these guys.

Another major step was taken - the rear toe links. Caution: technical babble ahead. This part is also really important because it keeps the rear wheels from steering, something I'd like to avoid. The angle, length, and position of the toe link all have an influence on dynamic toe. I don't want dynamic toe. At worst I would like a bit of toe-in on compression, which should cause the car to understeer rather than oversteer, a safe bet for a rear-engine rear-heavy car. The toe link is behind the spindle center line, but also really close to the lower control arm. By making it slightly longer than the LCA, it should toe-in just a tiny bit. I also angled it upward to somewhat negate the extra length (causes the link to "shorten" faster). To be honest, the exact position and length of the toe link were massive compromises forced by the hardware available. That hardware being the Toyota Avalon's original rear control arms, including an adjustable toe link, all of which I saved from the donor car. Isn't that convenient? It's also cheap.

So here's a pile of Toyota Avalon suspension bits I saved from the scrapper.

The adjustable link has a double-threaded turn-buckle type of nut. One side is reverse thread. You turn the sleeve and it extends or retracts the toe link from both sides. There are a lot of ways to make a control arm adjustable, but this way is free for my budget and should be easy to work on.

The chassis end of the toe link has a very high-quality greased bushing. It's more like a heim joint / rod end. The inner sleeve pivots quite a bit. I had to shorten everything to match the LCA length as close as possible. This end is solid rod so I did an overlap joint with plenty of beveling. I'm actually only using the reverse-thread end of the nut. I cut the inner tie rods off the steering rack and welded them into the normal-thread end of the sleeve nut. I could only do 1/2" of weld at a time before quenching, to keep the bushing from burning. I did it this way because the outer tie rod uses obscure yet beefy M15 threads, which you can't even buy on McMaster. So when you turn the sleeve nut, it also turns the M15 rod into the original outer tie rod. Geez explaining this car is difficult. Conveniently, the shackle end of this arm fits perfectly over the bushing with the same bolt hole size, so that saves me a bracket.

I just tacked the shackle in where the steering rack went for now. Sort of a "floating" toe link mounting bracket. This should be the only mod I do to the Toyota subframe.

Here's 0, 2, and 4 inches of compression. I could not discern any toe change to my naked eye. I also tried measuring the tire distance to the tube frame, but can't do it accurately enough. I would like to find a way to measure toe versus height, maybe something with lasers and poster board? I feel good about it for now.

2" up

All the way up. The built-in bumpstops in the coilovers should stop it well before 5", when many bad things begin to happen, like knuckle-to-rocker contact, upper ball joint range, sway bar hitting the tube frame...

This also means the rear frame can roll around the garage with the floor jack under the front part of the subframe. It might be time to merge with the Lotus frame...

TurnerX19
TurnerX19 UltraDork
2/20/22 10:25 p.m.

Make the inner end of your toe link vertically adjustable so you can dial it to your preference. A flat plate "false wheel" and two dial indicators on a T shaped stand with a heavy base is what I have always used to measure bump steer.

Mr_Asa
Mr_Asa PowerDork
2/22/22 8:47 p.m.
maschinenbau said:

In reply to Mr_Asa :

It's just to center the rotor on the hub until the wheel is tightened. The lug studs get it pretty close, but the plastic centering ring removes the slack and holds the rotor snug so it doesn't fall off while fitting a wheel. It shouldn't actually bear any load since the clamping and friction force of the wheel does all the work.

But I'm happy to accept free parts! 73.5mm OD x  62.5mm ID x 5 mm thick

Haven't forgotten this, just still digging around for a chunk of metal.  

maschinenbau
maschinenbau UltraDork
2/23/22 8:55 a.m.

In reply to Mr_Asa :

Thank you sir, no rush at all. Clearly I am not driving anytime soon.

Here's a rough positioning of the two frames, measured out to the Lotus wheelbase. Just a few tubes left until they become one. As soon as that happens, it will no longer fit in the garage. 

¯\_(ツ)_/¯
¯\_(ツ)_/¯ PowerDork
2/23/22 9:01 a.m.

This was already exciting and is getting more so with every post- I think it's really interesting how much your converted rear suspension came out looking like some sort of factory Honda setup, minus the bellcrank thing.

TVR Scott
TVR Scott SuperDork
2/23/22 9:24 a.m.

Looks pretty cool.  I like the conversion work you did on the "front" suspension to make it work in the rear.

maschinenbau
maschinenbau UltraDork
2/23/22 9:46 a.m.

Not gonna lie, I'm pretty worried about weight distribution. My spring calculations are assuming 65%, but what if it's more like 70%? How much is too much back there? I can put the battery and fuel tank up front, and the tires and track width are wider in the rear, so that stuff helps. 

¯\_(ツ)_/¯
¯\_(ツ)_/¯ PowerDork
2/23/22 10:00 a.m.

In reply to maschinenbau :

You'll be sitting in it so that's another 100lbs and change right in the middle.  You could start getting creative with other ways to move stuff forward- run the exhaust forward instead of back, I'm sure people will come up with other stuff.  A lot of your cooling system will probably be in the middle or front too I'd think?

dherr (Forum Supporter)
dherr (Forum Supporter) Dork
2/23/22 11:13 a.m.

This is getting cooler by the minute, great to see this becoming a reality. Agree on the weight distribution,  might handle and drive like a 930 Turbo smiley

Dusterbd13-michael
Dusterbd13-michael MegaDork
2/23/22 11:42 a.m.

As light as this thing will probably be, adding ballast should be a viable option.  Weigh more, but be faster due to balance. 

Mr_Asa
Mr_Asa PowerDork
2/23/22 11:49 a.m.
Dusterbd13-michael said:

As light as this thing will probably be, adding ballast should be a viable option.  Weigh more, but be faster due to balance. 

My thoughts as well.

nocones
nocones UberDork
2/23/22 11:57 a.m.

The LMP360 is about 65% rear with me in it   It handles fine.  It is however noticably better balanced with a passenger.  Without a passenger you very much are managing the rear but the front has sufficient authority to do it.  With a passenger the car seems to move a bit more neutral.  

Yours will be interesting though because the weight is probably a bit more concentrated in the rear even though the distribution is the same and will be quite a bit higher up then the Subaru engine is.  

I'm very interested to compare the cars at the challenge this year.  

Run_Away
Run_Away Dork
2/23/22 2:15 p.m.

That's killer, love the strut to SLA conversion.

I found those threaded spherical rods at the junkyard too (I got mine from a Camry), they're a pretty trick piece for such a pedestrian vehicle.

maschinenbau
maschinenbau UltraDork
2/23/22 3:17 p.m.

In reply to nocones :

I didn't realize it was that rear heavy. I'd say it handled much more than fine! My CG should be higher and more concentrated like you said, but I also have sway bars to help mitigate that. I am shooting for ride frequencies around 1.5 Hz (basically Miata with stiffer springs). Then adjusting shocks til it's good.

In reply to Run_Away :

Aren't those rod ends great? Very pleasant surprise indeed. I wonder if I can add a grease zerk. 

nocones
nocones UberDork
2/23/22 4:09 p.m.

In reply to maschinenbau :

Yep that's why if you look at a real LMP car (and a F1 car, and a Indy car) the wheels are sooo far back relative to where I put them on the LMP360.  They generally put the transmission in front of the diff because there is so much space behind the engine before they want the axle.  This effectively moves weight forward.  The Praga R1 and NP01 are more similar to the LMP360 but the run the rear axles at a pretty rearward angle to move the rear axle back a bit.  I didn't want to do that but may rebuild the rear suspension arms eventually to move the wheels back 2" or so.

Brotus7
Brotus7 Dork
2/24/22 8:02 a.m.

The body will help pull the cg forward a little.  If I estimate the cg location as where the body gets picked up squarely with my car, just about where the windshield meets the roof, maybe slightly forward.

What are you planning for a windshield? Lexan?

cruisermatt
cruisermatt Reader
2/24/22 8:48 a.m.

 

Looking good.. moving right along. One suggestion if you don't mind. Highly recommend doubling up the tab thickness where the pushrod bolts to the strut.  I would think two 1/8" plates like this would be ideal, leaving the original tab/tube in place:

 

Hopefully those control arm bushings last as toe links... but I predict you will be converting them to heims one day, for now, nice use of free parts. smiley

maschinenbau
maschinenbau UltraDork
2/24/22 9:20 a.m.

In reply to cruisermatt :

Yep. I should have made those triangular gussets pull double-duty all the way to the pushrod holes. I'm actually less worried about the knuckle tabs and more concerned about the same 1/8" tab thickness holding the rocker pivot, which should see roughly 3x the forces! With a rocker ratio of 2:1, the knuckle bracket only sees 1x corner weight (+ dynamics), the coilover sees 2x corner weight, and the rocker pivot will see the vector sum of 1x and 2x at 90 degrees to each other. Hence the support tube inline with the rocker pivot reaction. So I will be doubling that one up for sure. 

Those arm bushings were originally part of the adjustable rear toe-links on the Avalon, so this is possibly the best use for them. Assuming I didn't fry them during welding.

¯\_(ツ)_/¯
¯\_(ツ)_/¯ PowerDork
2/24/22 9:24 a.m.
cruisermatt
cruisermatt Reader
2/24/22 12:23 p.m.

In reply to maschinenbau :

I barely looked at the rocker pivot! what are you using as a bearing there? Sorry if I missed it earlier. Heard on the toe-link bushings. If they hold up on a car that's 1.5-2x the weight they'll be fine on this. 

Shavarsh
Shavarsh Reader
2/24/22 7:00 p.m.

I always enjoy watching your projects, following along.

maschinenbau
maschinenbau UltraDork
2/25/22 8:16 a.m.

In reply to cruisermatt :

Flanged sleeve bearings inside a close-fitting tube. I need to get a better picture of that area. It is greasable though.

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