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Learning how to build Lotus Seven replicas...together!
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PostPosted: Thu May 12, 2011 7:41 am 
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Location: New Zealand
I disagree with the method of reversing the tie rod end on the upright as it not as it was designed and as has been mentioned will mess with your akerman. I favour leaving it as is and instead designing your lower "A" arm to avoid the issue. In my opinion you do not have the lower ball joint mounted properly and that in the position you have it it will be to low and also not be at the right angle. The flat face where the short bolt is threaded into should intersect the centre of the long bolt. This is how it is mounted in the original arm. I have attached a picture of a mock up of how I intend to do it, please note it is only rough and intended as guide. I have since made a better one but have not taken a photo. I have drawn all this up on paper and am pretty sure that it will work fine.
In the first picture you can ignore the second ball joint as I was considering using this press fit one but as you can see is not as high.
Bruce


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Last edited by nisseven on Tue May 17, 2011 5:22 am, edited 1 time in total.
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PostPosted: Fri May 13, 2011 10:31 am 
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Location: bloomington/normal, il
nisseven wrote:
In my opinion you do not have the lower ball joint mounted properly and that in the position you have it it will be to low and also not be at the right angle. The flat face where the short bolt is threaded into should intersect the centre of the long bolt. This is how it is mounted in the original arm.


We welded a spacer on the bottom side of the top plate so that the ball joint sits at the right angle.
I’ll have to talk to my teacher next week about the other things you pointed out.



The two seniors who were working on the project with me finished school today and I have 12 school days left until summer. We are hoping to finish all of the control arms and paint the frame by the last day of school on June 1st


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PostPosted: Tue May 17, 2011 5:30 am 
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Location: New Zealand
Yes I can see that now. As I said this will place you ball joint to low if you want to leave the tie rod end in it's original position, otherwise it looks good.
Bruce


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PostPosted: Sat May 21, 2011 10:27 pm 
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How does the tie rod joint height affect ackermann? I'm not doubting you, because I seem to remember hearing somewhere that a low tie rod height is best for forward-facing steering arms. I just can't picture how moving that tie rod upward is changing the geometry in the left-right direction.


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PostPosted: Mon May 23, 2011 4:48 am 
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It will affect the akermann in this case because of the angle that the steering arm is on. Have a good look at your MX5 upright and you will see that it has a twist in it. If you move the tie rod end to the top you are effectively moving the pivot point inwards away from the wheel. If you look on here you will see that some have done this, but in my opinion it is not right. You will also see that some have heated and twisted the steering arm to correct the above and in my opinion this is probably dangerous, although it will correct the problem. It is possible to set the steering rack and tie rod as it was intended, you just need to get your lower ball joint higher on the arm. If you moved the tie rod to the top of the arm you will also need to find a tie rod end with a matching angle, which may not be to problematic as there will be someone on here who has done and can advise you, also the change in akermann may not be to bad, I don't know, all I do know is that it is not as Mazda designed it.
Have you drawn up the suspension geometry, you would use cad but I am a pencil and paper person but either way you can sort out a lot of these issues before you cut any steel? I would have thought that as an educational exercise that doing drawings would have been a component of it, in which case you would be able to see these issues and also looked at bump steer. I have just had a look back through the thread and see that you do have some drawings, well done. I also see someone has advise the new tie rod to use.
Bruce
I have edited this post as I had the twist of the steering arm the wrong way, I'm surprised no one noticed?


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PostPosted: Mon May 30, 2011 8:35 pm 
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Location: bloomington/normal, il
I spent last week final welding the rear end of the frame. School ends on Wednesday and we have gotten to a good stopping point for the summer and i will be in northern michigan all summer long so there wont probably be any more post until August.


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PostPosted: Mon May 30, 2011 9:57 pm 
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The voice of reason
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Quote:
Have a good look at your MX5 upright and you will see that it has a twist in it. If you move the tie rod end to the top you are effectively moving the pivot point inwards away from the wheel. If you look on here you will see that some have done this, but in my opinion it is not right. You will also see that some have heated and twisted the steering arm to correct the above and in my opinion this is probably dangerous, although it will correct the problem.


Moving the tie rod to the top of the arm will change the geometry, but I don't think our arms match the original ones anyway. THings will work out OK, if you make things the proper length to match and then check yuour bumpsteer.

I believe that heating and bending the arms is generally considered safe. THe subject has been discussed and people with reasonable experience weighed in.

Have a nice summer, I think you've done a good job on this frame and have something to be proud of! Not to mention something great to look forward too when you make more progress next year. I hope you getting to learn lots of pratical stuff. Plenty of folks never learn all sorts of basic stuff you get to learn when you build from scratch. Plenty more good stuff to do...

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PostPosted: Wed Aug 17, 2011 10:29 pm 
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After a summer spent almost entirely in northern Michigan it is time to go back to school. School starts on Monday and probably continue work on the car Tuesday.
I am excited to get back to work on the car.

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PostPosted: Sun Aug 28, 2011 8:18 pm 
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Getting toward the point of mounting the control arms to the frame. Any suggestions as to how to align everything perfectly?

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PostPosted: Sun Aug 28, 2011 8:40 pm 
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Fix the pivot points in space, independant of the chassis. Most builders run a long rod through the A-arm pivot points to keep everything aligned, then position the rods exactly where the plans specify in Y and Z, then fabricate brackets that rest on the rods and reach inward to the chassis.

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PostPosted: Tue Nov 15, 2011 12:27 am 
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So its been a while since the last update, but we have been making great progress on the suspension. All a-arms have been fabricated and now we are in the process of creating a jig to get all of the mounting points right and move closer to having a rolling chassis.


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PostPosted: Tue Nov 15, 2011 2:36 am 
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The voice of reason
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:cheers:

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PostPosted: Tue Nov 15, 2011 6:45 am 
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We are Slotus!
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Well Done! Keep up the good work, and keep us posted! "Roller Day" can't be far off now!

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PostPosted: Mon Nov 21, 2011 11:11 pm 
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We tacked the brackets for the rear suspension onto the frame today. Expect to fully weld them tomorrow.
getting closer and closer to a roller. Also got our engine to fire up last friday for the first time which is good news for having 230000 miles. :)


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PostPosted: Tue Nov 22, 2011 8:06 am 
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it looks like your rear suspension is more towards the back of the car than a lotus seven with a straight axle. This is not a problem if you make the back half of the car a little longer. By making the back of the car longer the rear fenders will bolt to a flat surface and miss the curve semi vertical surface at the very back.
keep up the good work!


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