LocostUSA.com

Hey I've been day dreaming about making a kit car or buggy for a real long time and I've decided its time to start. My donor will be by current car a 2006 scion xb which i've already rot rodded and runs great. A long time ago I read about kurt's kimini and how he designed it out of wood and I've going to do that also. So far I've been spending time using the racing aspirations app to get an idea of how my suspension should be. I haven't chosen seats yet so Im not sure how wide the frame will end up being somewhere between 46 and 50". I've made a tinkercad model to kind of get an idea of what looks cool. Also I made this table I know this project will take a long time and I didn't want to take up the garage or work in the cold so I figured I could do the wood design phase in my basement.

You should have no trouble fitting seat assemblies with all that room and minimal tunnel for shifting and coolant pipes. Extra room around the front of the engine for maintenance access and fuel tank is not a bad thing.

Are you going to use another scion for the ifs spindles and brakes with your rack?
Looks like the rc is moving a bit but I'm not familiar with that program.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Funny you mentioning that. Over the weekend I met up with Kimini's current owner - yup, she's still out there!

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I actually have a second set of front spindles I got a while ago. Pictured is an idea on how I can get an upper control arm on the spindle two side plates will be welded to the sides and bolted on but I was thinking about threading a hole in the top and use a uniball joint. For the rear upper I believe I can use a heim joint hooked up double shear.

I was thinking i could drill that hole for the uniball joint at an angle to get the required caster? Ill have to see if that is something viable. K772 threaded ball joints for all the bottoms, they don't fit naturally and I'll need to get a reamer.

I'll have to look into the roll center. I dont fully understand it yet. I wont be using the scion steering rack I was looking at UTV steering racks. There are a couple 4 seater utvs that weight around 2000lbs with big power so I think a rack from one of those could work.

Hey your book was a real good read. How you mentioned reversing the shifter assembly and then swapping the control cables, that was something I was thinking about for awhile, among some other theory bits really helped. Originally I was wanting to make to look more like a R5 or 6r4 but I think all the body work would really discourage me, like doors

So I went back to racing aspirations and I subscribed to see the roll center. After, I noticed the RC was closer to the ground than it was in this new screenshot and I lowered the upper control arm mounting point from 9" to 7 and it changed for the better?

Is there a minimum distance the control arm mounting points need to be spaced, vertically? I was trying to google that awhile ago and I didn't find anything conclusive.

I'd use vsusp and observe the rc in x and y balanced with camber gain while maintaining a reasonable vsa length to prevent wheel hop but everybody does it differently.

Here is an idea for the uca adapter using a tie rod.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

How is the nut on the tapered-pin ball joint accessed?

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

It is meant as a 5 minute mspaint for the broad strokes and not to scale.
The spacer and block thickness are set to provide the desired caster and enough room between them for the nut.
The easiest way is to tightened the nut before attaching the upright/spindle. Adjustment would be at the uca without loosening the nut or the spindle adapter.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I had thought about putting the adapter off the the side just like you pictured. I was eyeballing it and I was thinking to myself this looks like it may be at least 10 degrees, too much caster. But I went back just a few minutes ago and kind of got a bit better idea with some tape and string, dont laugh lol. I wouldn't say its exactly 5 degrees but its not 10 so I think this could be the way to go about making the adapters.

I've been kind of stumped about how to design this adapter for use with a ball joint. I'm not a material engineer so I just imagine an L shaped block of steel, the small leg for the ball joint, failing. Or am I wrong? This is my whole basis on thinking about using a uniball and a grade 8 bolt

An updated front end on VSup. I was reading about the fvsa, I didn't know about that.

A link to my design<

The block adapter you describe has been used on mustang spindles. I think you can find a pic on Lonnie's build.

Failing would depend on many things including material selection, cross section, the radius of the corners, an overload where the adapter is the first thing to run out of travel in bump, etc.

I assume the lca will apply chassis loads through the tires via lca mounted coilovers.
While strut type spindles are originally loaded through the strut, a locost uca normally is not.
The strut types also typically have a lighter duty lbj but you are addressing that already.

I'll take a look at the vsusp when I get a chance.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

In rev1, I made no changes to your geo except that tires compress on the bottom from loading so I removed 3/8" for that. This created scrub and threw off static camber with your existing dims. I setup the chart to show 3.5 degrees roll and while the rc is stable in y, it is very high and swings a lot in x. I'll retain your spindle dims, lca length, and track width but adjust the ubj for scrub and ucap, lcap, and uca length to balance rc location and stability with camber gain and vsa length.
MATTR SCION rev1 03172023

You are going to have a lot of kpi with these tires-wheels-fwd spindles. The diff between 1 inch of scrub and zero is about 0.75 deg kpi so I set it to zero for 15.75deg. Some oems have this much. I think how good or bad that is depends on how much the car is allowed to roll. If you'd like to compare, I have an old topic here where I provided most alignment specs for most cars. Fwiw, if I were designing a spindle, I'd start with an lbj as high and outboard as possible for the possibility of low scrub and kpi with a ubj near the rim lip and low profile tires with normal offset rims. I think this is why we see some oems with inverted lbjs (stud down).

I lowered the gc to 6 from 7 inches to level the lca at ride height. It helps with the geo. Stable lower rc in x and y through 3.5 deg roll, near zero scrub, 1deg pos camber at 3.5deg roll with 1/2 deg static neg camber. This is just a quick tweak to get it in the ball park. I'm sure you can improve this further.

EDIT: I think your wheel specs are off from what I would expect to see. The closest '04 scion xb wheel is 15x6.5 et35 with a 195-55-15 that would work well with a 205-60 or 50 but a 225-50-15 is a bit wide for a 6.5 wide rim. Et35 is 1.378" offset. If going aftermarket, use as much back space as will fit to design around. Verify what you are working with in vsusp and I'll try again.
Also, the geo might appear to be a level lca based on a level line but usually the tubing is not centered on a line between the pivots and ball.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Thanks for all the help so far. I looked into Lonnie's build and saw those adapters, a nice confidence boost. About the wheels I have, they're 8 inches wide with 23mm offset. They looked great on the XB but I see now the offset is working against me.

I changed my design aesthetically I don't want the upper width between the UCA to be over 28" and I was looking at my spindle and I had the lower ball joint distance wrong its more like 3" away from the hub. Anyways I noticed If you lower the track it starts becoming more compliant. I need to figure out what lower ball joint will be the best and it seems I need to find the lowest profile one and then go back to Vsup

mattr

@MattR

Also, Matt, Perry (horchoha) build his own for one of his builds that used a Ford T-Bird as a donor. You can see them in about the middle of the page Here. So, if you feel your fabricating skills are suitable, you can go DIY too.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886