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Learning how to build Lotus Seven replicas...together!
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PostPosted: January 13, 2009, 12:40 am 
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Auto Motive, My friends call me Motive
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Location: Spanish Fork, UT
Kurt, you are the master of the obvious. :lol:

I jest cause I know you have been called the suspension nazi and an a$$ for some of your comments. I actually enjoy reading your posts were you take the burden on yourself of keeping Locosters off the Darwin Award list. The problem with keeping stupid people from killing themselves is that they breed!

Anyone who does not think that heat warpage from welding is a major factor is kidding themselves. I use to be into building choppers. A guy I know shrugged off what everyone said about warpage and welded the neck on without checking it afterwards. when his bike finnally got on the road the thing would not go down the road strait without fighting the bars. His strearing stem had pulled out of verticle in the for/aft plane putting the front tire permenantly on its edge.

Its interesting to see how everyone trys to overcome warpage. Some people use a hundred clamps on their tables. some tack weld everything before finnal welding. some weld sections then align the different sections. We are all fighting a force that can not be overcome! "You must understant your opponent befor you can beat him, young grasshopper!"
The stratigy that I am taking is to not hard clamp anything, this way I know were the tubes are pulling befor I weld anything else on to a warped assembly. I didn't post the picture befor but I did have to use a bottle jack to spread the two front bulkheads before I welded them onto the bottom rails, but at least I knew were and how far things moved before I permenantly attatched them to the frame.


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staitening bulkhead.jpg
staitening bulkhead.jpg [ 142.67 KiB | Viewed 7586 times ]
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PostPosted: January 13, 2009, 1:11 am 
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Auto Motive, My friends call me Motive
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I just took a look at your websight again Kurt. I just wanted to say that I am not trying to copy you! There are ALOT of simularities between how we did things, like how the bulkhead at your feet ties into the bottom rails. I also wondering how far you tilted the drivers seat back. More specifically I was wondering how high the sholderstrap holes are from the floor. I realized the seat I used for my mockup sits up a coulple inches and I put the roll bar cross tube too high.


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PostPosted: January 13, 2009, 1:35 am 
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I was posting that comment for everyone and like you say, I think 99% of builders have NO idea how huge the forces are and the amount of warpage that happens.

I purposely don't look at too many other builds during my design to avoid any sort of comparisons in either direction. The seats are 20 degree layback and I tipped them back further until they felt right - I don't have a degree amount. The shoulder strap tube lines up with the cutouts in the seat, maybe a bit below them to meet the seatbelt maker's instructions. I seem to recall it being around 22" above the bottom rails.

It would have been nice if it was higher since it doubles as the engine cover, but in my case the engine is going to extend a ways through it, oh well.

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PostPosted: January 26, 2009, 2:14 am 
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I've been alittle busy paying the bills but I finnally got around to finnishing an upright enough that it will make sence to see were I am going with my design. I still have to get the proper sized hardware and some new steal as I used some rusty scrap to make sure everything would work together. I have spent alot more time than I thought I would designing these. I am actually on version #4 as I would change the design to both make it stronger, simple, and easier to manufacture. I'm really happy how they turned out. It is just over 6 pounds lighter than the cast iron ones I originally thought about using! Still need the caliper mounting bracket though. I've also never liked designs that put a hemi joint on the end of a single shear post. Since all the bolts are double shear I am going to use reducer bushings on the 5/8" joints to reduce weight and it will give me alittle bit more room for adjustment of the top ball joint/steering arm. Camber is adjustible by putting shims or washers on the two bolts between the main body and the steering arm piece. The bolt going though the upper b/j and the slot in the top insert is then tighted to give the assembly its strength.


Attachments:
File comment: basic components CNC milled
upright 001.jpg
upright 001.jpg [ 149.97 KiB | Viewed 7399 times ]
File comment: Grind the corners of the top insert to fit into jigging slots
upright 003.jpg
upright 003.jpg [ 140.95 KiB | Viewed 7397 times ]
File comment: Self jigging with plently of weld area for a strong connection
upright 004.jpg
upright 004.jpg [ 148.36 KiB | Viewed 7392 times ]
File comment: bend outside tab to 90deg. with top insert plate. This is angled to put the hemi in the center of its travel at ride height.
upright 006.jpg
upright 006.jpg [ 143.99 KiB | Viewed 7390 times ]
File comment: outside
upright 009.jpg
upright 009.jpg [ 150.81 KiB | Viewed 7387 times ]
File comment: Completly boxed in. Prior to full welding.
upright 011.jpg
upright 011.jpg [ 147.48 KiB | Viewed 7383 times ]
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PostPosted: January 26, 2009, 5:33 am 
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Motive - I like your approach, it looks like a Locost Porsche 962 upright!

Does the top member (that takes the top spherical and steering rod end bearings) bolt to the upright, and so allow for shims to be added removed to adjust camber?

I take it that the design does limit you to using hemi bearings rather than longer life ball joints?

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PostPosted: January 26, 2009, 7:50 am 
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Man, Motive, that upright is very, very clever. Where's a tip-of-the-hat emoticon when you need one?

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PostPosted: January 26, 2009, 11:49 pm 
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Quote:
Camber is adjustible by putting shims or washers on the two bolts between the main body and the steering arm piece.


Does that answer your question PUK? I find it funny how everyone worries about the life of rod ends compared to ball joints. I'm useing 5/8 "teflon lined rod ends from Jack and don't think service life will be a problem. When you consider how few miles are actually put on these cars its almost a non-issue when you use a large enough rod end. Plus the cost of a rod end is usually alot less than a ball joint (price a miata lower). I can afford to wear out a couple and still be ahead. That being said, I could adapt the design to use a ball joint by simply welding an insert with a taper inside the current lower mount tube. Geometry would be changed but still in a useable range.

Thanks Jack, If you want a set, I still need more rod ends!


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PostPosted: January 27, 2009, 4:15 am 
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Arhh yes question answered, and that explains the elongated whole in the top plate :oops: .

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PostPosted: January 27, 2009, 9:39 am 
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I like your thinking outside the box with putting the camber adjustment on the uprtight instead of the chassis mounts or a-arm's. I was thinking of a few ways to do that too, but yours simple and elegant. Overall I really like your upright design...and I may be forced to steal some ideas from it. :wink:

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PostPosted: January 27, 2009, 10:38 am 
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Driven5 wrote:
I like your thinking outside the box with putting the camber adjustment on the uprtight instead of the chassis mounts or a-arm's.

The cool thing is that it adjusts camber only; toe and wheel alignment are unchanged so fast changes can be made in the pits.

Porsche originated the idea back in the 1970's (and may have even borrowed it themselves.) There's a picture of the setup in one of Staniforth's books.

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PostPosted: January 27, 2009, 11:26 am 
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Interesting...I've always seen the shim thing done on the inboard/chassis side of the a-arms instead. I wonder why I haven't seen this style used more often compared to the inboard shims.

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PostPosted: January 27, 2009, 2:35 pm 
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Driven5 wrote:
Interesting...I've always seen the shim thing done on the inboard/chassis side of the a-arms instead. I wonder why I haven't seen this style used more often compared to the inboard shims.


You should have seen it.. We used it on the back of Our FSAE car, and the 4 prior to it...

Looks like a nice robust upright.

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PostPosted: January 27, 2009, 2:42 pm 
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Well spank me twice and call me Shirley...We did! How in the world didn't I remember that??

Boy do I feel dumb. :oops:

Ok Mr. Idesignedmostofthefsaecarmyself, do you remember what the reasoning was for not considering this type of adjustment on the front as well?

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PostPosted: January 28, 2009, 1:51 pm 
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Beautiful, simple and easy to build :D

But, how do you tighten the bolts for the top & bottom pickup heim joint bolts? I see you could weld the nut inside for the lower joint, but the upper one needs to be able to slide to adjust camber. Correct?

The only way I can figure it from the pictures is you plan to remove the bolt on hub and reach inside the upright through that hole. If so, that seems to over complicate camber adjustment that could be very quick.

Are you planning to cut access holes or slots to fit a wrench through the outside face of the upright?

Or am I missing something very obvious. As usual :?

James


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PostPosted: January 28, 2009, 2:51 pm 
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Driven5 wrote:
Ok Mr. Idesignedmostofthefsaecarmyself, do you remember what the reasoning was for not considering this type of adjustment on the front as well?


I think the major one was that you can't adjust camber without affecting scrub radius. The advantages in the front is it locks in your link geometry, and doesn't require you to adjust toe for camber changes, and is pretty simple, you also can change ackerman and KPI with just a set of upper brackets. The disadvantages are that it does weigh a fair bit more, and the mentioned Scrub radius. The other problem is that your shim stack/boltheads can have issues with running into the brake rotor on applications with low KPI, low Scrub. For a street car running FWD wheels with higher 8-10 degree KPI it probably won't be an issue.

And always remember FSAE is a strange world where Suspension design does in fact have a correct answer.

It looks like on his design the UBJ bolt is designed to completely clear the slot so it is free to move when new shims are installed.

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