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Learning how to build Lotus Seven replicas...together!
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PostPosted: Tue Mar 03, 2009 2:01 pm 
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Perhaps it's not a spherical bearing, but a solid "rod eye" or whatever you call them? If it's not one of those already it could be, although there would be some bending/buckling load on it's shank that's not desireable.


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PostPosted: Tue Mar 03, 2009 2:40 pm 
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But then it'll bind in bump/droop...

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PostPosted: Tue Mar 03, 2009 2:57 pm 
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If the Forward LCA is perpendicular to the frame and you replace either the shock end or the inboard heim with a solid bushing, it should work fine then. Or you could replace the outboard hiem on the rear lca with a plate and clevis simular to the one on the upper arm.
Phil


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PostPosted: Tue Mar 03, 2009 3:13 pm 
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True, but nothing in our cars are truly rigid - everything's compliant to some degree.

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PostPosted: Tue Mar 03, 2009 4:13 pm 
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KB58 wrote:
But then it'll bind in bump/droop...


Not if its only the link under the shock mount thats a solid rod end. In that case it should be fine.

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PostPosted: Tue Mar 03, 2009 4:33 pm 
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I'm pretty sure the link under the arm that runs toward the rear is attached with a solid joint to resist twist. Also the shocks would contribute greatly to the stiffness of the assembly as the reasonably solid bushing on the bottom wont like to twist in that direction to much. He did state that this is Off the shelf circle track parts. Which makes me think they work acceptably.

Daniel

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PostPosted: Tue Mar 03, 2009 4:40 pm 
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It looks like he is using these:

http://www.speedwaymotors.com/Steel-Rod ... ,1534.html

If so, nicely done! It would be tough to get it any lighter than this. It looks a lot like a ford festiva/aspire suspension only much less bind.

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PostPosted: Wed Mar 04, 2009 12:29 pm 
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Miatav8,MstrASE,A&P,F wrote:
It looks like he is using these:

http://www.speedwaymotors.com/Steel-Rod ... ,1534.html

If so, nicely done! It would be tough to get it any lighter than this. It looks a lot like a ford festiva/aspire suspension only much less bind.


Yes. This is an established design called a strut type LCA. Very common in much heavier asphalt stock cars. I carefully went through the full range of bump and droop and the lower spherical bearing, or any other component, remains free of binding.

This set up would not be recommended for a street application where significant wheel travel is desired or required. You might get away with it if you went with a ball joint in lieu of a spherical bearing at the lower upright mount. UB machine makes these using ball joints also!

I thought the assembly would work well in my specific application. It is a proven design and very light weight. I am sure if it can hold up to a V8 stock car requirement it is likely overkill for a 1080# lotus. All the components are available off the shelf from UB machine, Speedway, etc. This will help me in getting replacement parts even when I am traveling. As long as UPS delivers there, I can get replacement shipped overnight!

The cost is fairly Locost too. The lower control arm unit is only about $50, powder coated, and well constructed.

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PostPosted: Sun Mar 15, 2009 8:29 pm 
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After 3 trys and 2 weeks I finally got the front suspension control arms figured out. I revised the LCA fron the trailing strut to a leading strut. I get more more than enough bump and droop and the camber gain is not significant with the new layout.

The only thing is I wish I had is a narrower overall width. With 13"x10" wide wheels and only 2" backspace all dictated by the chosen Mustang II spindle and 10" brake rotor squeezed by only 13" diameter wheels, it was the best I could do. I could go with narrower wheels and tires but I may go with a smaller spindle and brake rotor somday. A larger diameter wheel would greatly increase my tire budget and change all the gearing. Need to keep the tire diameter small to heat up the Hoosiers quicker on a 60 sec autocross run.

Everything is a compromise.


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South Bend Region SCCA http://www.sbrscca.org/

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PostPosted: Sun Mar 15, 2009 9:50 pm 
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That looks like a lot of scrub right there. I hope you've got pipes - my chicken wing arms had a hard enough time with my 13x10's, and I have 5" backspacing.....

G

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PostPosted: Sun Mar 15, 2009 10:25 pm 
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When I read that you decided to go with Mustang II spindles over the Fiero spindles I figured we'd see something like that.

Here's what you could have had with Fiero/Chevette spindles. The wheels are 13x10 and there's a 1" spacer behind them.

Image


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PostPosted: Sun Mar 15, 2009 10:35 pm 
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SkinnyG wrote:
That looks like a lot of scrub right there. I hope you've got pipes - my chicken wing arms had a hard enough time with my 13x10's, and I have 5" backspacing.....

G

I thought guns aren't allowed on SCCA events :?

Moti :lol:

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PostPosted: Sun May 10, 2009 5:32 pm 
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I haven't posted in a while with Solo season starting but I managed to get the final front suspension design complete with steering system rough layout. Everything is fitting nicely with no suprises so far. It helped a lot to have a flat and square build table and measure everything twice before cut and weld. The chassis is off the build table for good at this point. Should have it rolling with a painted chassis mid summer latest. 8)


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“Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead.”- Locofinn

SCCA D Modified autocross special. Scratch-Build completed 2013.
South Bend Region SCCA http://www.sbrscca.org/

Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356
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PostPosted: Mon May 11, 2009 6:57 pm 
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You are making good progress. I like the addition of the cross piece between the upper spring mounts. It should counter the twist that would otherwise be there with such a large lever arm.

How did you fit the oil cooler? I am struggling with mounting mine. It is tight. Too far forward and there is not enough width. Too far back and you are into the waterpump pulley. Maybe the 12A oil cooler is just a bit shorter than my 13B cooler.

Chuck

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PostPosted: Tue May 12, 2009 8:15 am 
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Chuck, Keep in mind my motor set back several more inches to the rear than yours. As you can see from the photos I have plenty of room for the cooler to be suspended from the top frame rail. It is just resting there for now to make sure I cleared the steering components. I will have some sort of suspended bushing mounts to attached it. I have plenty of room to mount a couple of small fans to the cooler also. Having the oil cooler away from the radiator and motor should help with keeping things cool a possible. I am also planning significant engine bay exhaust side vents similar to what Jeff Underwood did on his BEC Locost.


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“Building a whole car from scratch is a 1,000 little tasks, done 1 task at a time, while thinking 10 tasks ahead.”- Locofinn

SCCA D Modified autocross special. Scratch-Build completed 2013.
South Bend Region SCCA http://www.sbrscca.org/

Link to my build log:
http://www.locostusa.com/forums/viewtopic.php?f=35&t=3356
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