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Learning how to build Lotus Seven replicas...together!
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PostPosted: December 21, 2017, 12:43 pm 
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Thanks for the pictures and explanation Zetec7. BTW they make little slugs you can fit in those slots to help hold the adjustments or make sure you can set them to repeatable numbers. May not help you now, but for others there is a picture below.

What I planned for Car9 was to mount the suspension with little bolt on tabs. The tabs bolt to the sides of the frame rails, which are 1"x2" for a little extra strength. Adjusting the suspension would mean changing tabs with the rod end holes drilled in different places. I saw this done on a formula car once way back when and it seemed elegant. I don't expect to do much changing but wanted to be able to try some different things at the beginning when I first run the car. Other builders can just weld on the tabs.

With the 1"x2" tube I expect the tabs could be welded to the 2" face on each side which keeps the welding heat off the faces of the tube which carry the load. I like the way Zetec7 bracket also distributes the load and helps strengthen the frame tube.


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PostPosted: December 26, 2017, 3:15 pm 
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Some of my parts have been coming in and I am not completely happy. First to look at is my Helix Pinto/Mustang II 2" drop spindle. These are very similar to the parts that Wilwood makes, but they have missed the mark somewhat.

The basic issue is that these spindles have flats machined on them where the ball joints go. That in itself is fine, but the way that it has been done is very poorly thought out. It appears there was little thought put into these, I don't really understand how that happens. It was probably designed by the CEO in his spare time in the men's room because even showing a diagram or picture of what was happening to an actual engineer would have cost him enough money to buy a bottle of scotch.

Here is the issue, the flat for the lower ball joint cuts substantially into the body of the upright. It is completely unnecessary to do that.

I am thinking of doing some heavy welding on this spindle to fill in the notches cut into the upright body and also to build up the shape near the disk rotors and then put new mounting holes into the spindle which will move the ball joints about an inch close t the rotor surface. I have a apir of stock rotors coming while I make a choice on fancier brakes that I will use to help figure out the spacing. This change woud make a Pinto 2" drop spindle much more like a Miata spindle. This is to reduce the amount fo scrub radius and also make wheel choices easier.

These spindles did cost 1/3 the price of a Wilwood piece. So I can afford to practice welding on them. They could have made a good unit for the same price though.

The spindles are said to be 1040 and also potentially heat treated, but I have not put it into a hardness tester, so I don't really know.


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PostPosted: December 26, 2017, 5:09 pm 
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Location: BC, Canada. eh?
I must say that the machining looks nice, though!

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PostPosted: December 26, 2017, 7:15 pm 
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A radius on the sharp inside corners might be a good compromise. My solstice spindles are aluminum - i don't think they are any thicker than yours, so the minimum cross section might be more than enough for Car 9. I could measure the min cross section tomorrow if you'd like.


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PostPosted: December 27, 2017, 11:25 am 
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To that point, Locoster have been built with Transit tie-rods as balljoints for years. There is significantly less material in the threaded shank than what remains on your uprights. I think you'll be fine.

If you're really concerned, do what Sean said and use a flap disk or die grinder to make that lip into a radius.

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PostPosted: December 28, 2017, 5:55 pm 
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The machining itself looks fine. It's just odd where it was placed. It appears the metal is about 1/2" at the narrow point in the notch. The Wilwood parts do not have any notch there at all and I don't think it's actually required. When I get the ball joints in that I ordered I'll take another picture and we'll see what it looks like.

Andrew the part I am concerned about is the notch on the bottom part of the upright which carries the load of the spring/weight of the car. Do they use the tie-rods on the bottom of the upright too? As you're saying though, the Miata lower ball joint is attached with bolts on a tongue from the ball joint itself, so it's likely this is thicker than that tongue is.

I will try not to become distracted by turning welding of the uprights into an entirely other project! :rofl: I was looking forward though to doing that work mostly so I could move the locations of the balljoint tapers and get a piece with less KPI and also less scrub radius. I'm not sure really how much difference the scrub radius makes though. There are plenty examples of track cars with a lot of scrub radius but it's not clear what that means really.

Anyway, onwards and upwards!

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PostPosted: December 28, 2017, 7:18 pm 
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Yes. I recall seeing it done several time. Modernbeat used rod-ends for his lower ball-joints: http://locostusa.com/forums/viewtopic.p ... 01&start=8

You said its 1/2" thick - how wide is it? I'm guessing around 1".

Obviously your car is heavier than Modernbeat's but I bet there is still more metal there. I'm with you - I wouldn't machine it that way but if their legal people are fine letting the part go then its probably okay. If nothing else you'll still be lighter than the car it was intended for.

If it makes you feel any better, look at how much metal actually connects the upright and lower ball-joint on a Caterham. A little bit of well used steel or a lot of poorly used steel can get the job done.

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PostPosted: December 28, 2017, 10:31 pm 
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That's a classic "don't do that" in engineering texts, but almost all General Motors spindles look like that. There's just so much metal there it's not a problem.

Take your Dremel and some of those otherwise-useless polishing bobs and make the notches shiny if you're still worried about it. Or fire up the angle grinder and remove some of the excess metal from the upright portion until the notch is gone. Once the notch is cut, the extra thickness at the ends isn't doing anything useful and can be removed without any problem.


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PostPosted: December 29, 2017, 12:56 am 
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Just to be clear the notch I am concerned about is at the top of the photo. I'll get a better picture showing the cross section tomorrow. It's at the top of the photo but that's the bottom of the upright where the load is much higher. I was guessing it's about 1/4 or 1/3 of the cross section cut into. I think it's more than half the strength of the part gone, maybe 2/3.

I can keep making progress and don't need to decide what to do about this for awhile. I ordered some parts but the ball joint collars with cheap ball joints are backordered now at Speedway. I think I'll call them and upgrade to better ball joints with less friction. Still pondering on the variety of adjustable ball joint collars that are offered for oval track use....

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PostPosted: December 29, 2017, 1:21 am 
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Here is my Mustang II upright. You can see some of the clean up I did.


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PostPosted: December 29, 2017, 1:38 pm 
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Thanks for that picture it helps make clear what I am talking about. B85, can you fill in a couple of details for me? Just to help me visualize more, are those stock Mustang II rotors? What size and offset rims are you using? In your picture is is clear that the machining did not affect the strength of the part.

Here is a better close up of the Helix part. Because it is a drop spindle the metal is angled upwards from the lower ball joint mount. When they machined that flat they cut substantially into the upright body. The flat is about .9" thick but the cut reduces the upright to just a little over .5". Somewhere the left hand was not talking to the right hand. Either the flat is machined too aggressively or the body of the upright should have curved away just a bit at that point. Neither would have cost the manufacturer anything at all and would have made the part several times stronger.

Furthermore you can see from pictures that the WIlwood pro spindle avoids these problems. In fact they bother to build in a nice radius in the forging at this point for the upper ball joint mounting hole.

For the moment I will continue to make progress. I am going to start another thread though on the subject of after market spindles. This Helix part is marketed as having been optimized by computer design and also has claims about the materials used. I am going to ask around to find a friend with a Rockwell hardness tester and also a hand held spectrometer for metal alloys and find out what this is actually made of. Also get some expert welding advice for this.


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PostPosted: December 30, 2017, 12:45 am 
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The wheels are from a 1989 Mustang GT. Their after market ? 15" x 7'. Don't remember the offset. But they fit under the Mustang fenders.

I ground all the sharp cuts into radius's. No problems yet.

I can't remember if the vented rotors were Mustang II ? If they had them then I think so ? I'm old. :roll:

I will keep looking for the info.

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PostPosted: December 30, 2017, 4:18 am 
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Hi B85, actually if you can just remember or measure the brake rotor diameter, that's what I'd like to know. The stock ones are 9.25", which I think is fine for our cars unless you actually run on a track. The stock Pinto was around 2200 lbs., so that gives a nice margin.

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PostPosted: December 30, 2017, 10:18 am 
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Marcus, i think you may be over thinking this. I agree that the design/machining could be done a bit better. However, you are saying there is about 1/2" of 'metal remaining. There is little leverage in that location. The ball joint would typically be attached to the control arm with 1/8" steel plate. Then there is the attachment to the chassis. Again, usually 1/8" steel "U" brackets welded to 1/16" steel tube with a lot more leverage applied.

I'm not discounting your concern. it certainly could have been done better. I just think that in a Locost application, there is little to worry about. I will say that I am not a trained "injinear", so take what I write with a grain of salt.)

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PostPosted: January 2, 2018, 9:24 am 
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Hi Marcus-
The gates opened this morning and I'm allowed back into the fold... Hope your bunch had a good Christmas. We all exchanged the "gift that keeps on giving"... The flu!

Meanwhile, back at the ranch... I bought M-II/Pinto 2" drop spindles from somebody on E-Bay. They had similar "cuts" to what you're describing, but not bein' a Enga-Neer, I just bolted 'em up and went on my merry way.
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Both are crappy pictures, but I think you can see the cutouts in the body of the spindle. So far, that's one item on the Slotus that I have NOT broken. YMMV, etc. My set was designed for dirt track racers that probably weigh in at 3000 lbs or so.

Also, on the front end I went with what was called a "hybrid" brake set-up, got it from Speedway Motors. Designed to go with the M-II/Pinto spindles, it used a Ford Granada rotor, 11" diameter vented disc and GM-style "Metric Chassis" calipers. (Only GM part on the car!) It was sold as a kit, came with br@ckets (EEEK!) to fit the spindles and the calipers, wheel bearings, etc. Fit just fine inside my 15 X 10 steel "telephone dial" front wheels.
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I don't seem to have a picture of the actual brake rotor/caliper, sorry...

Other'n that, how the hell are ya?

Peace, Love and Busted Spindles-
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