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Learning how to build Lotus Seven replicas...together!
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PostPosted: February 17, 2013, 6:37 pm 
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Posthumane,

I just noticed that I missed your first post answering my question. The axles are different but share many parts. The 7.5 ring and pinion and carrier will swap between them. The ranger drivers side axle fits in the fox housing. This last week I replaced the 4 lug fox axles with 2 right side ranger ( 5 lug x 4.5) axles. The 9" drums also trade over. these pics are of the fox when I first got it, and after trading axles and cleaning off the 4 link mounts. i almost forgot, the fox is Aprox. 59" WMS to WMS and I estimated ranger to be about 56"/ But you know that, right!
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Attachment:
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I don't know if you have run across "The Ranger Station" site? It has lots of good info.

Ron

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PostPosted: February 20, 2013, 4:10 pm 
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Posthumane,

How much clearance is there between the rear tires and the frame at ride height? How close does the tire get with one wheel at or close to max bump?

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PostPosted: February 20, 2013, 7:49 pm 
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I haven't measured it but with one wheel in full bump it comes very close to rubbing. However, the wheels I had on for testing had 225/60-14 tires, and I plan on running 205/60-15 which bulge out a little bit less. I can take an actual measurement when I have the axle back in the car.


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PostPosted: February 25, 2013, 4:28 pm 
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Posthumane,

I have a 1" gap at ride height. If one side should make it the full 3.5" bump, the tire would be 1/2" into the body. From what can be estimated by rotating the axle in the SketchUp drawing. And yours looked close.


Oh yeah, those 1/16 6011 are Hobart rods at $10.99 per lb.

Ron

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PostPosted: March 10, 2013, 5:23 pm 
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Posthumane,

Do you have any updates on your build? Decide on a color yet?? What are you doing for front fenders?

At any point did you measure how long the 2.3 is, say from back of the block to front of the pulleys. If you already mentioned it in your log I missed it.

I'm designing a new frame to give 2" of clearance on each side. To me a small price to pay to have the "7" as right as I can make it :)

Ron

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PostPosted: March 16, 2013, 5:40 pm 
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Hey Ron, I haven't decided anything with regards to body work. I'm focusing on getting to the rolling-chassis stage right now, after which I'll focus on going from that to the driving-under-it's-own-power stage. Only once that is done will I start on any body work and making it road legal. I haven't even settled on making it look like a Lotus 7 but may instead decide to go with a more enclosed body.

With regards to car progress...
I hadn't had much time in the last few weeks to work in the garage. Part of that was because I was away for a work related trip to Vancouver, which was actually fairly refreshing. Sometimes it's nice to get away from the snowy prairie. Anyway, just before I left I had received my two Hayabusa shock assemblies in the mail so I've spent most of my effort since I returned trying to figure out the best mounting solution for those. They have a 730lb/in spring so an approximate 0.5 motion ratio was in order to give me reasonable wheel rate, with further tweaks as necessary after the car is on the road.

I had planned to mount them in the traditional style (lower mount near the outer end of the lower control arm), with the outer mount 12" our along the 16" control arm and the shock at a 45* angle. This would give me a motion ratio of 12/16*sin(45)=0.53. However, I ran into interference issues between the steering rack/tie rod and the spring when the steering is at full lock, so now I'm considering other solutions. I was almost settled on a pushrod operated inboard suspension, but was not totally happy with any of the packaging options. I'm now almost settled with mounting the shock above the UPPER A-arm, with the lower end attached directly to the outer pivot point and the shock at a 30* angle to the A-arm for a 0.5 MR.

Hayabusa shocks:
Image

Floor, seat, and steering column in place:
Image


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PostPosted: March 17, 2013, 12:09 pm 
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Posthumane'

Glad to see you're still plugging away. Working out the packaging issues take up a lot of the time we would rather be building. I think the community could use a half dozen new frame plans designed around the other (non Miata) donors we have today. Do you think the shocks can live between the motor mounts and the rear inboard UCA bracket. The shorter end of the bell crank being inboard leaves more space close to the engine. Were you going to have an alternator or something else in those spaces?

I like the way you worked the seat in.
I picked up a pair of Honda Civic seats over the weekend. When I measured across the rails I got 19" so... Listing options but it's going to add time to the build anyway it's done.

When you get a chance can you get a picture of the front from the top down? My old eyes are having trouble working out just how the rack sits.

Nice well lit workspace!!


Ron

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PostPosted: March 17, 2013, 9:18 pm 
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Hey Ron
I'll try to get a pic of the front end and some measurements of the engine and transmission a bit later this evening when I head back out to the garage. It's -12 degrees celcius (about 10 F) right now and my workspace isn't really heated so I can't stay in there for long periods. To mount the thunderbird rack I added a riser going across the frame of 1.5" RHS and attached brackets on top of that. The centre of the rack is about 10.4" up from the bottom of the frame and only about 0.5" ahead of the front track centreline. This actually gives me more than 100% ackerman so it could be moved forward, but I didn't want to shorten the tie rods. Sounds like a lame excuse, right?

The seat took a bit of fenangling to get it in there. Although it's on sliders it acutally doesn't move foreward and back all that easily since the leather cover is jammed right in against the frame.

I had considered putting the shocks laying horizontally by the motor mounts, but the steering got in the way again. It's fine on the passenger side, but the drivers side has the steering shaft attaching to the rack right where the bellcrank would have to be. I've had to scrap my idea of attaching the shock to the UCA outer pivot because of a stupid oversight: the bolt that runs through the spindle to attach the rod end, which I was going to use to mount the outer shock bracket, has to be able to turn as the wheel is steered. Duh! I dunno why I missed that the first time. So now I've settled on having the shock between the LCA and frame like I had originally planned, but moved further back. I managed to squeeze it in just behind the steering rack with the upper shock mount basically in line with the rear UCA pivot.

Thanks for noticing my well lit workspace! I just did a small upgrade to the lighting, replacing the two 100w incandescent bulbs I had with a pair of 1-2 splitters into four 24" flexible extentions, topped off with 4 26w CFL bulbs. Small change, but it made a big difference in the useability of the space.


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PostPosted: March 18, 2013, 7:07 am 
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Posthumane,

I'm all for leaving the rack alone if possible. The new frame for my " 7 " will be set up around the stock Mustang rack, and which ever spindles I end up with, held in place with the control arm geometry worked out by " string computer " and their brackets held where they need to be. The frame will be built to them. The less machining done the more " Locost " the project remains. :)

I found this picture after the last post. The picture was taken from the bottom with the frame flipped.
Attachment:
shocking .jpg
shocking .jpg [ 255.74 KiB | Viewed 1547 times ]


Interesting, right! There's a certain elegance to simple solutions ( yours not that one ). I've read where others have encountered clearance issues when the steering is turned fully to the stops. The tie rods will come back a bit on the side of the direction of the turn ( left side, left turn ).

I can't spend much time in the shop when the temp. falls below 50!!! :lol:

Ron

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PostPosted: March 18, 2013, 7:55 am 
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doh.... forget it. You already said it was flipped. :oops:


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PostPosted: March 18, 2013, 10:19 am 
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Posthumane,

Another idea! I know the angles on the bell crank are wrong,... but using 1" x .125" tube, 1/8" oil lite bushings, and a 1/2" rod, supported by an " U " shaped suspension brackets on either end?

Attachment:
offsetbellcrnk.jpg
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This way the push rod could attach to the LCA at the ideal location, right next to the LBJ.

Would you have room for that?

Ron

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PostPosted: March 18, 2013, 3:49 pm 
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Hmm, that's actually a pretty nice looking design. One thing I'd be concerned about is the torsional rigidity of the connecting tube. The force produced by the spring at the full 2.5" deflection on a 'busa shock is ~1825lbf. Lemme try some calcs, just for the helluvit...
Second moment of Inertia Jt = pi/4*(Ro^4-Ri^4) = pi/4*(.5^4-0.375^4) = 0.03355583
Shear modulus of A36 steel G = 11,500,000 psi
Torque T = 1825*2in = 3650 in-lbs
length of tube L = 6in
Angular deflection = T*L/(G*Jt) = 3650 * 6 / (11500000*0.03355583) = 0.056751623 rad = 3.25 degrees.
So, at 2.5" of shock deflection the tube would twist 3.25 degrees, assuming a 2" shock bracket. With your push rod at 45 degrees, you would need a 1.5:1 bellcrank for a 0.47 motion ratio, which would give you a 3" pushrod bracket at the bell crank. 3.25 degrees of twist results in 0.170" of pushrod travel, or about 0.24" of wheel travel. I suppose one could live with that since it would only reduce your wheel rate by 4.8%, or you could make your tube slightly larger.

Anyway, that was a bit of an academic exercise, but I kind of wanted to go through it just for some practice. I do think your idea is a good one and I will definitely consider doing that rather than the offset shock as it provides the opportunity for varying the motion ratio much more easily. Did you make the model of the busa shock yourself or did you find it somewhere? If I were doing that setup I would mount the shock upside down with the reservoir at the bottom. The other end was a clevis (as opposed to the bushing on the reservoir end) and is also much lighter, being attached to the rod as opposed to the body.

With regards to your Honda seats, is it possible to narrow them by cutting their frames down the centre and re-welding?


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PostPosted: March 18, 2013, 8:37 pm 
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Posthumane,

You have no idea how much I would like to be able to run numbers like that. I just look at other known successful designs and over build to be safe. Oh well :|

The Shock came from the SketchUp " Warehouse " someone else shared it with that community. I chose the end that was most similar to the end of yours opposite the reservoir to show how it might attach.

I'm considering a two part solution to fitting the Civic seats. The seats can and would be narrowed, but not the full amount. The other part, if I can figure out how, would be to bring the bottom, A1 and A2, tubes back at almost the same angle as the J1 and J2 tubes, like the earlier Donkervoort roadsters. In the pictures I've collected it looks like around an additional 2" in width is gained at the rear bulkhead. The exact tapering back to the shock towers and then to the even narrower back top tube still needs to be worked out. It look like the front and back bottoms of the rear fenders curve in and hide the difference in width from front to back.
Or may it's just time to update my eyeglass prescription. :roll:

It's something to think about while I wait for the snow ( again ) to melt so I can get back outside where the Ranger is parked and finish pulling the motor and trans.

Ron ( Staying away from the lemon snow cones :shock: )
Builder of a STranger 7

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PostPosted: March 20, 2013, 5:52 pm 
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OK....scratch the Donkervoort treatment. It doesn't lend itself to using a live rear axle or the high offset wheels I'm using. It sure does allow the room to route the exhaust over, down, and out the back.

Ron

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PostPosted: March 21, 2013, 12:29 am 
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Here's a shot of how I'll probably be mounting the busa shocks up front.
Image
This hopefully gives an idea of the steering rack placement that you were after Ron. Here's a closeup of the mounting arrangement.
Image


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