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Learning how to build Lotus Seven replicas...together!
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PostPosted: August 3, 2007, 1:24 am 
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I wanted adjustable toe and camber for the rear end. So I elected t to retain the upper rubber bushing for some compliance needed for toe adjustment. The toe adjuster is a LH/RH turnbuckle connected to the lower pivots of the upright. Camber is adjusted via adding shims(to be made) between the two parts of the upper control arms. The two 3/8 pins slide in housings on the inboard side of the control arms, there is one hole in the middle for a bolt to act in tension to clamp against the shims. The outer part slides in and out. Bushings were welded into the front bulkhead to accept suspension bolts. all holes were reamed to .375 to provide a light press fit for all suspension hardware. another update in early September, hopefully i will have some springs and dampers by then from summit so i can make spring mounts, bellcranks,etc.

Andrew


Attachments:
reamer.JPG
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weld in bushings.JPG
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uca camber adjust.JPG
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left rear corner.JPG
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rearsub.JPG
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PostPosted: August 3, 2007, 2:53 am 
NICE WELDING!!! Looks good!!!


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PostPosted: August 3, 2007, 6:13 pm 
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Thanks for the compliments.

Well Im now back at work away from the project for the next three weeks or so, but im still getting lots done design wise on my spare time. Ive worked out the bellcrank and pushrod dimensions for the rear suspension. Basically im using a series of arcs and intersections to determine were the points need to be located. By having the damper operate in only one plane, the pivots can be located easily in deltacad. The motion ratio I'm looking for is 1:1. It takes a bit of trial and error to get it close to correct, but as you can see in the drawing, the ratio is kept within 1:0.99 and 1:1.02, not perfect but good enough and there is no decrease in rate during compression.

unfortunately I did not get accurate measurement of the diff when I was home, but the Idea is to integrate the diff mounts and the damper mounts to save weight by simplifying the packaging.

Andrew


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rear push rocker.jpg
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PostPosted: September 7, 2007, 3:38 pm 
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Update from early September.

Well I finally have a set of coilovers. I previously went through a really bad experience with a certain vendor, but thats in the past now. I reordered them from Naake suspension, they answered all my questions, returned my call and emails, they were overall good to deal with. Anyone looking for QA1 stuff like odd size rod ends, I would recommend these guys.

Up front Im using 8235 dampers and 200 in lbs springs, in the back 8234 and 300 in/lbs springs. The stroke is 3 inches. pushrod bearings are QA1 XRM-6-7 and XML-6-7. (.375 bore and 7/16 LH and RH threads)

The front center damper mount is fabbed from 1x2 .100 HSS. It will receive further gusseting. also aluminum sheer panels will be fastened behind and below the dampers. This will stiffen the front structure and will act as a shroud to duct air in and around the dampers as I hear the smaller body dampers get hot easily during prolonged use.


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IMG_2660.JPG
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IMG_2655.JPG
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PostPosted: September 7, 2007, 3:44 pm 
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....cont.


Front pushrods fabbed from 7/8 x065 DOM. bungs made from 3/4 x .188. LH and RH thread for simple ride height adjustment.


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IMG_2657.JPG
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IMG_2658.JPG
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PostPosted: September 7, 2007, 4:18 pm 
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...cont.

As for the rear end, I didn't really get that much accomplished this time home.

Bell cranks and mounts were fabbed up for the rear. I started work on the rear damper mount/cross member. It is made from 6061-t6, I didnt get a chance to trim it down, because the old man borrowed my jigsaw and didnt return it. There will be steel hard points welded up and riveted into place on the cross member to add shear strength were the dampers bolt in.

The aluminum parts will be riveted with solid rivets, the exact same one you see on most aircraft. I thought id install a few to demonstrate the difference between a regular blind rivet and a driven solid rivet. And of course before any final assembly of an aluminum structure, the parts will get an acid wash, alodine, epoxy primer, and an application of adhesive sealant between mating surfaces before final riveting.

Anyways still lots of work to do on both subframes next time Im home, including mounting the diff, making the rear pushrods, and further bracing on the rear subframe. After that a build table is next and i will be able to jig up the subframes and start building the rest of the chassis.

Andrew


Attachments:
File comment: red line indicates were trimming is required. black line is steel fitting welded to subframe
IMG_2641.JPG
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rivetbefore.JPG
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rivetafter.JPG
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File comment: drill through the head, pry it off with a pin punch, then drive out the tail.
rivet removed.JPG
rivet removed.JPG [ 56.94 KiB | Viewed 12648 times ]
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PostPosted: September 7, 2007, 5:25 pm 
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Updated work in progress drawing, I like the long tail look better, but Im years away from making the body.


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PostPosted: September 7, 2007, 6:34 pm 
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Location: Michigan
looks awesome! seems like you are taking the same approach I was considering not too long ago, but I am years away from even starting anything so I can't wait to see how this turns out. keep it up!


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PostPosted: October 21, 2007, 5:29 pm 
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Finally back at home for some progress. I spent 42 days at work this past rotation, twice as long as normal, but I was rewarded with a promotion+raise.

On with the progress. continued work on the rear end, mounted the diff, completed fab on the aluminum crossmember, mounted brake line brackets, made pushrods and mounts etc.

Still lots of work to do including triagulation on the rear sub. I also need to prep/prime/seal rivet the crossmember, I might get to that on monday, we'll see.

Other good news, I have arranged a location to start building the chassis, it will be available in mid November. Im really looking forward to that, so are my parents to get me out of their garage.

Andrew


Attachments:
File comment: checking travel/steering input for brake line location, tab to welded in
front brake.JPG
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File comment: more bracing required, maybe get that done tomorow. NAS shear bolts for mounting the X-member
rear.JPG
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File comment: tab to be welded in.
rear2.JPG
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File comment: steel standoffs to transfer the loads
rear3.JPG
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File comment: i need to upsize the holes to #20 for the 5/32 solid rivets
rear4.JPG
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File comment: everything needed to clean, convert, prime, adhesive sealant bond the aluminum. more on that later
5.JPG
5.JPG [ 90.7 KiB | Viewed 12142 times ]
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PostPosted: October 21, 2007, 10:07 pm 
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..Cont.

Just fitted the 94 miata inner cv's on the 90-93 axles, and the length is perfect, the inner cv sits right in the middle of the slip joint. I just need to get the cv centering bore turned down to slide right into the supra stubs. I will deal with that next time home.

So why didn't I just buy a miata diff and carrier. It seems they command quite the premium here in BC, on Ebay also, and that doesnt even get you an LSD, also the toyota unit was cheap and I should be able to source different ratios for no significant cost.


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CV.JPG
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SUPRASTUB.JPG
SUPRASTUB.JPG [ 91.83 KiB | Viewed 12111 times ]
MIATA cv.JPG
MIATA cv.JPG [ 67.17 KiB | Viewed 12107 times ]
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PostPosted: October 23, 2007, 12:33 am 
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My week off has come to an end so progress will cease for the next three weeks.

I pretty much finished up the rear subframe fab work. All thats left is to make two struts that connect the diff mount to the front lower corners of the subframe(seen in red). Relieved the crossmember on the rear lower edge to gain just more than 1/4 inch of clearance between it and the diff. Also countersunk the holes above the diff for flush rivets. Probably not necessary, but cleans it up a bit. In addition added gusetting between the front bulkhead and rear facing tubes, the front and rear diff mounts and the UCA mounting tabs. Overall everything pictured weights in at 166 lbs. My weight target is 1000 lbs dry.

Andrew


Attachments:
8.JPG
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7.JPG
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6.JPG
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PostPosted: October 23, 2007, 7:59 am 
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As always, looks great. I just hope you have one rock solid way of jigging it up when you do the main chassis so it all comes out straight! Keep it up!


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PostPosted: October 23, 2007, 2:46 pm 
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thanks. I didnt take pictures during the build/welding of the subframes, but the workstand was levelled, and everything was clamped solidly before welding. The suspension pivots all remained flat and square and measured the same before and after welding. For the build table I intend to make 8 posts that will locate the lower suspension pivots in their correct locations above the refernce plane (the bottom of the floor). these will bolt to the work table and hold the subframes up. Then build the chassis inward from the subframes.

However I am perpared to accept a certain degree of warp, Id be crazy if I said it would be made straight/parallel/level without warpage. The idea of making the subframes first was to do most of the welding isolated from the rest of the chassis, so if they warped one way, i could jig them the other way to keep things straight. I have never built a car before so I hope this will work out for me.


l8tr


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PostPosted: October 24, 2007, 12:25 am 
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Location: Edmonton
WOW!! looks great! :D


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PostPosted: October 24, 2007, 9:06 am 
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Location: Michigan
Didn't mean to imply that you didn't know what you were doing, I'm sure you do, just something that came across my mind. It's very difficult to keep a chassis straight, esp when you fully weld it. Just one of the many challenges of a project like this, but it sounds like you have a plan.

airframefixer wrote:
thanks. I didnt take pictures during the build/welding of the subframes, but the workstand was levelled, and everything was clamped solidly before welding. The suspension pivots all remained flat and square and measured the same before and after welding. For the build table I intend to make 8 posts that will locate the lower suspension pivots in their correct locations above the refernce plane (the bottom of the floor). these will bolt to the work table and hold the subframes up. Then build the chassis inward from the subframes.

However I am perpared to accept a certain degree of warp, Id be crazy if I said it would be made straight/parallel/level without warpage. The idea of making the subframes first was to do most of the welding isolated from the rest of the chassis, so if they warped one way, i could jig them the other way to keep things straight. I have never built a car before so I hope this will work out for me.


l8tr


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