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Learning how to build Lotus Seven replicas...together!
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PostPosted: Mon Apr 30, 2012 6:59 pm 
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i really like the front rocker setup


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PostPosted: Wed May 02, 2012 5:56 pm 
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^thank you!

I got my steering linkage all in and working, it's pretty cool to be able to sit in teh seat and spin the wheels side to side :o

I also got the rest of my front tubes in minus two that i would like to add but need to confirm they'll clear the shocks once installed.

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I also used the common (or similar) radiator mounts that many are using around here.
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I need to redo the rear upper arms and add a few tubes here and there and then starts the fun of the chassis welding.

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PostPosted: Wed May 02, 2012 6:17 pm 
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Your steering rack does not line up the the inboard a-arm mounts. You may want to look into this if you wish to prevent bump steer.


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PostPosted: Wed May 02, 2012 6:25 pm 
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Just a note on the front suspension. If you are using motorcycle shocks, the lever ratio is backwards. The way it is set up, you will only have 1-1.25 inches of travel . Even if you are using a long travel shock, the range of motion at the pivot will only give you <1.2R of useful travel R= pivot to pushrod distance. Did a lot of modeling of inboard pushrod suspension. Ended up going outboard for simplicity. Pushrod works better when designed correctly.

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PostPosted: Wed May 02, 2012 6:55 pm 
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itsu-san wrote:
Your steering rack does not line up the the inboard a-arm mounts. You may want to look into this if you wish to prevent bump steer.


correct - there needs to be a shim in there to line it up just right. it's floating left & right a bit in the adjustment slots as well in the pics. i'll line it all up and do the bump steer shimming adjustment once everything is on the car after being fully welded and what not.


bremms wrote:
Just a note on the front suspension. If you are using motorcycle shocks, the lever ratio is backwards. The way it is set up, you will only have 1-1.25 inches of travel . Even if you are using a long travel shock, the range of motion at the pivot will only give you <1.2R of useful travel R= pivot to pushrod distance. Did a lot of modeling of inboard pushrod suspension. Ended up going outboard for simplicity. Pushrod works better when designed correctly.


how so? i've tested ~4.25" of shock travel which matches up to just about 1:1 with wheel travel. I've also run the as-built dimensions through my suspension analyzer software and it agrees with my testing - something like .954 motion ratio. I only expect to use about .2" of wheel/shock travel on the track but wanted to leave room for height adjustment

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PostPosted: Wed May 02, 2012 7:23 pm 
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I've actually found that bump steer varies quick insignificantly with steering rack width and inner tie-rod horizontal placement. It's the height that's much more sensitive of an adjustment. If I wanted a "perfect" steering rack width, I would've had to take another two inches out of my rack, which is impossible. But it doesn't make too much difference. Now, if I moved the rack up or down by 1/8", it would've been a pretty significant change in bump steer characteristics.

You're making tons of progress--that's awesome.


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PostPosted: Wed May 02, 2012 8:16 pm 
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Looked at it again. you do have a ~45deg angle on the pushrods. and your lever ratio on the rocker is about 1:1.5 or 1:1.4. That gives you about 1:1 at the shock as you indicated. Most use R6 or R1 shocks that only have about 2 inches of travel. 1.8 to the bump stop and about 2.25 to bottom. If you are using a shock with 4.25" of travel then that is perfect. MY BAD... Should have looked at it more closely before posting. Forgot about the pushrod angle and you are not using motorcycle shocks.

Sorry.. Carry on..

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PostPosted: Wed May 02, 2012 9:36 pm 
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mattrogers wrote:
I've actually found that bump steer varies quick insignificantly with steering rack width and inner tie-rod horizontal placement. It's the height that's much more sensitive of an adjustment. If I wanted a "perfect" steering rack width, I would've had to take another two inches out of my rack, which is impossible. But it doesn't make too much difference. Now, if I moved the rack up or down by 1/8", it would've been a pretty significant change in bump steer characteristics.

You're making tons of progress--that's awesome.


yeah, ideally to get zero bump steer in full range you have to have the rack at exactly the right height and exactly the right length side to side. That gets expensive. I'm settling for perfect height and as far forward as I could reasonably put it to get as much ackerman as I can.

thank you! how about a race to driving? I need some further motivation :-)

bremms wrote:
Looked at it again. you do have a ~45deg angle on the pushrods. and your lever ratio on the rocker is about 1:1.5 or 1:1.4. That gives you about 1:1 at the shock as you indicated. Most use R6 or R1 shocks that only have about 2 inches of travel. 1.8 to the bump stop and about 2.25 to bottom. If you are using a shock with 4.25" of travel then that is perfect. MY BAD... Should have looked at it more closely before posting. Forgot about the pushrod angle and you are not using motorcycle shocks.

Sorry.. Carry on..


phew, you had me worried! it's easy for me to zone in and not realize I missed something obvious.

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PostPosted: Thu May 03, 2012 9:21 pm 
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Tongboy wrote:
thank you! how about a race to driving? I need some further motivation :-)
You're on! What can possibly go wrong?? :boxing:


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PostPosted: Fri May 04, 2012 8:06 am 
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Tongboy wrote:
mattrogers wrote:
I've actually found that bump steer varies quick insignificantly with steering rack width and inner tie-rod horizontal placement.


yeah, ideally to get zero bump steer in full range you have to have the rack at exactly the right height and exactly the right length side to side.


I gotta think you are going to have noticeable bumpsteer with your current setup because of your overly-long tie rods. How that affects you and your driving is for you to decide, plenty of cars running around with bump steer with the owners still having plenty of fun.


I just noticed the slicks you intend to use, your single element rear upper arm, which I considered below borderline for street tyres, is in no way suitable for those wide slicks. You have 100% torsional loading in the lower arm along with a leverage factor. But it's probably fine as long as you accelerate gently and never, ever touch the brakes....


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PostPosted: Sun May 06, 2012 1:32 am 
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cheapracer wrote:
I gotta think you are going to have noticeable bumpsteer with your current setup because of your overly-long tie rods. How that affects you and your driving is for you to decide, plenty of cars running around with bump steer with the owners still having plenty of fun.

I just noticed the slicks you intend to use, your single element rear upper arm, which I considered below borderline for street tyres, is in no way suitable for those wide slicks. You have 100% torsional loading in the lower arm along with a leverage factor. But it's probably fine as long as you accelerate gently and never, ever touch the brakes....


agreed, the rack isn't the ideal length. I should be able to dial out 99% of it at a single steering angle, we'll see how bad it is at other angles and if need be i'll replace it with a custom $$$ rack.

The rear uppers are being are in the process of being replaced with real uppers.

I cleaned up around the car to prep it for chassis welding

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wrapped the exhaust up with the rear mount
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Pulled all of the control arms off to weld up and the exhaust to get it ceramic coated
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pulled everything off the chassis to start welding it. There is still a number of parts to get welded on the chassis - steering wheel support and plenty of body tabs but I think it's ready to do the majority of the welding and then address the smaller parts as they go on.
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PostPosted: Sun May 06, 2012 10:26 am 
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I don't think that muffler is going to be enough. The S2000 engine is one loud motha.

As far as your bump steer goes I'm betting it won't be bad at all. The longer steering rack rod will give you a longer arc than the suspension arms and in theory should give less variance than if you had shorter rack rod. Most people who have trouble have shorter rack rods which have more arc change in a short distance.

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PostPosted: Wed May 09, 2012 1:42 am 
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carguy123 wrote:
I don't think that muffler is going to be enough. The S2000 engine is one loud motha.

As far as your bump steer goes I'm betting it won't be bad at all. The longer steering rack rod will give you a longer arc than the suspension arms and in theory should give less variance than if you had shorter rack rod. Most people who have trouble have shorter rack rods which have more arc change in a short distance.


we'll all find out together :) I need to meet 100 db as measured at an scca event

Chassis is getting TIG welded this week, SO many welds! my hands are still sore from chasing all the threads on the control arms after they got welded.

I found a great deal on a haltech iq3 logging dash so I picked that up. Now starts the fun of laying out the wiring setup for the car, should be a lot easier than my last project since I don't have to care about any of the emissions or OBD2 stuff.

I dropped a solid 400 bucks on AN bolts & associated today. You think about bolts a lot differently when you spend 25 bucks on one...

I have to take a week off of work before the end of next month (terrible, I know.) as such i'm trying to get all of the plumbing & wiring parts lined up so I can have a productive week worth of working on the car.

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PostPosted: Tue May 15, 2012 1:39 am 
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Cleaned up all the emissions components on the motor

Image

then I threw it on the scale - complete w/all accessories except AC, no fluids - 408lbs
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PostPosted: Tue May 15, 2012 3:26 pm 
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That's pretty light for the whole thing. It will be VERY loud with one flow through muffler. I'm running a single Borla 2.25" and my Volvo mill is loud. I'm switching to 2 2.5" Burns stainless cans. ( already have these.) Should be a little quieter than what I have now.
The s2k motor will be deafening over 6k. See how it goes, you can change if you need.
The locost exhaust is so close to your ears it needs to be a bit quieter than a standard cage. NOTHING is as loud as a rotary.. Loud and obnoxious, makes your ears bleed. Shrieking, shrill and hard to tame. Kind of like a few girls I dated.

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