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Learning how to build Lotus Seven replicas...together!
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PostPosted: Mon Mar 06, 2006 11:33 pm 
Tonight's progress.. almost have one upright finished.. talk about some precision work!!! The hole in the upright had to mate up with a machined cylindrical surface on the back of the hub which was exactly 3.30" in diameter. How do you do that with just basic garage tools, no lathe, and a yard full of scrap steel?

Well, heres how I did it...

Here is the surface my uprights have to mate to:
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The OD of the cylindrical portion is ~3.30"
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Next, you grab a cold one out of the fridge. If you are Irish, you grab a frosty Guinness.

Next, I had some old driveshafts in the backyard that happened to have an ID that was just a hair too big, but was CLOSE to what I needed to go around the hub. I sliced off two 3/8" width "rings" of the tube and then cut out a peice of the ring with a hacksaw. Once I had a gap in the ring, I then just held it around the hub tightly and tacked the gap closed, obviously being very careful not to get any welding slag in my ice cold Guinness.
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Voila, perfect fit!
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So, once I had that, I cut out the holes in the uprights.. and welded the rings from the backside of the upright:
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The hub fits perfectly, sitting in place with the whack of a rubber mallot, with zero slop in the hole. Now i just need to weld in the lower pivot and the upper bracket (tommorrow's job)
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And here it is with a rough "suspension" layed out on the car. looks like it might work...
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 Post subject:
PostPosted: Tue Mar 07, 2006 12:27 am 
A crappy sketch of how the lower rear arms will look:

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 Post subject:
PostPosted: Tue Mar 07, 2006 1:22 am 
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Location: So CALIFORNIA
Wow well Done!

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I'll keep an eye out for you!

To err is human...
I am more human than most.


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PostPosted: Tue Mar 07, 2006 9:44 pm 
Today I swung by a store called Racemart. They are primarily a sprint car parts supplier, but they had the clevis and left handed heims that I needed. After pressing in the new 1/2" sleeves in the poly bushed heims, I dont think I want to use them. The poly bushes come out way too easy in a side load situation for my comfort.

So, I picked up 2 LH 5/8" heims, 4 RH 5/8" heims, and 2 5/8" clevises that use a 3/4" thick mounting tab. They werent cheap, but I've got to do this right the first time. For the clevis, I'll probably end up using two 1/8" spacers/washers and then make the mounting tab out of a small peice of 1/2" steel plate that will get welded to the A arm. (coincidentally have lots of that kicking around the garage as well).


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PostPosted: Wed Mar 08, 2006 12:43 am 
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Joined: Mon Aug 15, 2005 10:13 pm
Posts: 7048
Location: Charleston, WV
Dang Datz, you crafty devil. Nice work.


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PostPosted: Tue Mar 14, 2006 10:34 am 
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Joined: Wed Jan 18, 2006 11:48 am
Posts: 94
Datz510,

If you get a chance could you give some ball park dims for the rear diff arrangement? How far back from the locost lower frame member and how high?

I've been planning to use a AWD subaru as a donor car, but I am now leaning towards the 240sx.

I wanted the Subaru mostly for the rear diff (R160), but was also going to use the for corners.

The 240 sx uses an R200 diff (Q45 and 300zx use the R230 IIRC) which is similar in size to the R160.

Thanks


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 Post subject:
PostPosted: Thu Mar 23, 2006 2:30 pm 
Its been a couple weeks of setbacks.. I've been sick for the last 2 weeks, so havent been able to to much recently.. :( Add to that that my roommate's air compressor nearly burned my garage down. Luckily he caught it right after it had filled the garage with smoke and before any flames started. So, my plasma cutter is now inoperable without air.

Despite all that, the last two days I've been working on the locost again.. I worked on finishing the rear uprights first. They are ALMOST done. Several weeks ago, I sourced a stick of 1/2" ID DOM tube to work as the lower pivot for the uprights and cut two 6" sections for the lower pivot. An 8.5" grade 8 bolt slides through this tube at the bottom of the upright with a heim joint on each side (these are held captive with male spherical washers).

Now, I've been concentrating on getting all the hardware I need (nuts, bolts, etc) to get the details of the car together. Also, getting ready to order some swaged tubes for the toe adjustment of my rear arms (see the sketch above).

Over lunch today, I'm headed out to a 4x4 fabrication shop to see if they can help me by threading some tube for my rod ends. Will be really nice if they can, then I can get my A arms built.

jl, I'll see what I can do as far as ballpark measurements. So far, it looks like the 240sx rear suspension is an ideal setup for the Mcsorley 442 chassis width. Now that I'm getting closer to having a rear suspension, I can tell you that this rear suspension looks like it will allow for up to 10" wide wheels in the rear. The diff, while a bit on the heavy side is very very common now in junkyards, so obtaining spares will be very easy. Also, LSDs are available in both viscous and mechanical forms, so there are a lot of traction control options out there. The viscous LSD is available in some production 240sx's, so you could get one right from the start. I'll be waiting until I get my car on the road to see if I want to go with an LSD or not. My only fear with the LSDs is that due to the lightweight nature of the car it might upset the handling balance when it engages.


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PostPosted: Fri Mar 24, 2006 9:58 am 
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Joined: Wed Jan 18, 2006 11:48 am
Posts: 94
datz510,

Thanks for the reply and the info.

The viscous and mechanical lsd r200 diffs are in ALL infiniti i30's from the 90's if you need another option.

I've been doing a lot of research :D


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 Post subject:
PostPosted: Sat Apr 01, 2006 11:11 am 
Got a jig made for the lower rear A arm tonight. Welded up one of them. Turned out REALLY nice!!

I SHOULD have all 4 rear A arms done by the end of the weekend!!! :) :) :)

Also, I found a really neat trick for prototyping A arms. If you are using 5/8" heims, the 3/4" tube slips RIGHT over the ends of the heims. So, what you do is build a C shaped bracket to tackweld to the bushing rings of the A-arm, then off of that bracket, you tack on one or more peices of 3/4" box tube to locate the upright where you need it. The nice thing about the box steel is that it can be held perfectly in plane using welding clamps, so it makes on-car prototyping possible. Once you hve the prototype arm mocked up, you then transfer that to a jig by putting the mockup on a peice of wood and build around it with 1x2 wood and drywall screws as seen below. The finished product is a perfect match to the mockup, but is perfectly flat.

Then, I played with clearancing the throttle body for the space frame and ended up boogering it up somewhat. I'll have to head to ace hardware tommorrow AM to see if theres something I can use to fix it.

Here are some photos of the latest work:

The jig I made for the lower rear A arms:
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Here is the dummy arm I made up to make the jig from:
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The dummy arm and the 90% finished product... turned out really nice!!!
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The one thing I have left to do is weld a 3/8" steel tab to the arm for the clevis on the toe-adjustment member:
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Here are some more photos of the arm:
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Some of the other things I've done... Got the shifter and plate in place after relocating some of the trans tunnel crossmembers:
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Started working on steering as well ( I need to put in another U joint where the rod end is located, to get the steering shaft around the exhaust)
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A nifty part I fabbed up fr the porsche steering rack. This makes it really compact so I can get around the front of the engine with the steering linkage:
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The rack even got cleaned up a little. Still need to change over to some rod ends or balljoints on either end of the rack though, as I really dont like the stock porsche 914 rubber bushed ends:
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Looks like it'll work.. :)
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 Post subject:
PostPosted: Sat Apr 01, 2006 6:32 pm 
Finished both lower arms and the prototype for the upper arm ... now working on making the jig for the upper rear arms. :)

Looking at the design of the lower arms, I decided I'm going to place the coilover just to the rear of the halfshaft at the junction of the tubing on the lower arm. So, I'm clearancing the upper arm to allow a coilover to pass just behind it. Should work ok I think. I know this will place some extra stress on the rear arm, but since it is made from .25" wall tubing, it should be fine I would think. What do you guys think?


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 Post subject:
PostPosted: Sun Apr 02, 2006 12:18 am 
You should be fine 1/4" wall tube is pretty strong.

And the arm looks pretty good, if the others come out like it you should be better off than me, I had to make 3 sets of A arms before I was happy with a set.


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 Post subject:
PostPosted: Sun Apr 02, 2006 12:43 am 
My arms are mixed 1/4" wall and 1/8" wall tubing. The tube that the heim threads into is 1/4" wall, the rest of the tubes are 1/8" wall. I figure that 1/8" is more than adequate.

I think that prototyping the arms first with the 3/4" box steel is the way to go. You can adjust the prototype as you are making it to get the lengths exact, allowing for the proper range of adjustment in the heims.


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 Post subject:
PostPosted: Sun Apr 02, 2006 12:01 pm 
I think that the weak point in your design is 2 places, the heim itself, if it is put under too much stress and screwed out the way it is will bend just past the locking nut, it is just aluminum. Also the clevis I think that there is a chance (very slight) that it could pull free, and break open on the end away from the thread, especially if you hit a large bump or a curb or anything that would cause the wheel to want to pull away from the car. i would think that a heim would work better there. of course if you hit something hard enough to break the clevis I would have more to worry about than just the clevis braking.

There would be a minimal weight penalty vs strength gained.


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 Post subject:
PostPosted: Sun Apr 02, 2006 7:53 pm 
The problem with putting a heim in place of the clevis is that you only want one axis of motion, which the clevis gives. With a heim there, you'd have a part of the arm that wouldnt be triangulated, with joints at 3 corners.. Wait till you see how I attach the clevis... there will be no way that it'll come loose or tear the tubing. The clevis will actually be located about 1" outwards of the chassis tubing that you see. For the photos, I just set it on the chassis to get an idea of how it will work.

Also, the heims I got are all heavy duty and are high grade steel. I just checked them with a magnet and the magnet sticks. ;)

The lower rear heim, I've screwed in another 3/8" or so, as I found out that my passenger side halfshaft is borderline too short. I may have to put a large spacer behind the drive flange on that side to make it work. What I didnt know about the 240sx drivetrain is that the stock differential is shifted about 3/4-1" towards the passenger side, so since I centered it, the pass side halfshaft is a bit too short.


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 Post subject:
PostPosted: Sun Apr 02, 2006 10:48 pm 
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Joined: Mon Aug 15, 2005 10:13 pm
Posts: 7048
Location: Charleston, WV
Very impressive!


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