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Learning how to build Lotus Seven replicas...together!
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PostPosted: Mon Oct 20, 2008 10:11 pm 
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Sorry to hear about your troubles Andrew. Fiberglass is a somebitch, I hate that stuff.

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PostPosted: Sun Nov 09, 2008 10:09 pm 
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I'm past it - my fiberglass days are over for now. Once there is a mold its great but until that point I have no desire to deal with it. Back to the metallic stuff....

I ended up with the standard locost Summit/Jazz 8 gallon fuel tank. I am currently using Summit's mounting kit but I may replace the lower straps with something more robust than 1"x1/8" steel strips since that is all supporting the tank right now.

My shocks also showed up. I ended up going with Gaz on all corners. I need to get the mounts welded up before I convince myself tackwelds will be enough to keep the car off the floor long enough to take a picture.


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PostPosted: Mon Nov 10, 2008 9:47 am 
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With vertical fastening of the control arm pivots, how will you limit suspension travel to prevent bending the rod ends?

The mold layup appears to be one piece. I would use dividers on the narrower side. This appears to be the sides and not the top/bottom. Do you have release wedges?

For setting up the dividers, Hobby Lobby has an oil based modeling clay for setting up behind the divider, away from the setting glass. Any material could be used for the divider as long as it gets covered in silver duct tape. Once the glass cures, the divider is removed, the glass released (easier now than when the whole thing is glassed), then waxed/pva'd where it will contact the setting glass of the other half of the mold, etc.


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PostPosted: Mon Nov 10, 2008 1:52 pm 
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Until I can redo the upper forward mounts, ratchet straps seem to be pretty good limiters for droop travel. :lol:

The lower mounts are fine otherwise in terms of travel. I'll probably bevel the inside edges of the mount just to make sure it never contacts the nut or shank of the rod-end.

When I originally did the calcs to figure out travel, I saw 17 degrees as the published deflection for these rod-ends on Summit's site. I assumed (incorrectly), that was from center to bind rather than bind to bind. The lowers allegedly had double the required travel but the uppers in the front had barely enough. Well when I started putting stuff together, something wasn't right up top; I checked Aurora's site and found the error in time to not make it on the rear upper arms.

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PostPosted: Mon Nov 10, 2008 3:37 pm 
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have you thought about boxing (at least one side) of your steering arms and upper/lower shock mounts? It is probably good engineering practice even if you don't expect loads to travel in those directions...

what about doing something to keep the tube the upper shock mount is on from twisting?

just some observations i just had.

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PostPosted: Mon Nov 10, 2008 6:25 pm 
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I'll eventually box all of those tabs. I was waiting to get the main part of brackets welded first and check clearances. I won't argue that those caps are easily the largest contributor for bending stiffness and strength.

I ran that tube through Cosmos awhile back. It will probably start to fail from a 4G bump under full weight transfer or a 5+G bump under no weight transfer. Something else will probably be damaged at that point as well. Under normal use, I think it will be okay.

I may still add a bolt in cross brace between the left and right forward shock mounts. It will not do much to help react the vertical component of the shock's force but it will help with the horizontal component and to resist the tube twisting.

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PostPosted: Fri Nov 14, 2008 12:57 am 
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Aurora should have some high misalignment rod ends available with at least 20° center to bind (check the MIL-spec ones)

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PostPosted: Fri Nov 14, 2008 9:28 pm 
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I was looking at the high misalignment rod-ends earlier but ran into a few issues. They would defiently solve the rod-end contacting the bolt at the end of its travel but the shank of the rod-end is also hitting the inside edge of the mount. I could hack off enough material to allow it to clear but I'd be concerned with the remaining edge margin.

I also used 2"x1"x0.125" ERW tubing for the mounts; the 1/2" high misalignment rod-ends need 0.875" between mounts. I only have 0.75".

Great idea but unfortunately I think I have screwed this one up too much to not have to redo the brackets.

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PostPosted: Wed Dec 03, 2008 2:04 am 
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The front mounts are fixed....

........and for the big news; it rolls.


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PostPosted: Wed Dec 03, 2008 2:54 am 
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Great job!
Did you calculate chassis stiffness of your frame?
It looks fantastic, very close to what I have in mind, only you built it faster than the speed of geology and I don't :lol:

Moti, going to get some furniture dollies to acheive a "roller" status too.

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PostPosted: Wed Dec 03, 2008 10:00 am 
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Wow, that looks great. You do good work, fast too!!

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PostPosted: Wed Dec 03, 2008 10:56 am 
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a.moore wrote:
........and for the big news; it rolls.


OOOoooh....sixteen-wheel drive! How many differentials does that require?

-dave

ps. Did you cut down those movers dollies, or did you find them that size to start with?

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PostPosted: Wed Dec 03, 2008 9:27 pm 
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Thanks again guys. Its finally going to start to roughly resemble a replica of a strange looking British sportscar.

Blackbird wrote:
Great job!
Did you calculate chassis stiffness of your frame?
It looks fantastic, very close to what I have in mind, only you built it faster than the speed of geology and I don't :lol:

Moti, going to get some furniture dollies to acheive a "roller" status too.


My last run through ANSYS had the frame at 3400 ft-lbs/deg but I've also added some heavier tubing since then in a few areas. It could probably be stiffer since my total roll stiffness is around 570 ft-lbs/deg; I've read you generally want about 10x this for the chassis stiffness.

It only costs $10/corner to achieve roller status when HF is having a sale - it took Ron Champion atleast that and his won't do doughnuts in the garage. ;)

HF sells 2 sizes of dollies; they seem to love pushing the large ones but they also sell the smaller size which is rated for 1000 lbs/dolly. I can't take credit for the idea since I stole it from Keith Tanner's site.

dhempy wrote:
OOOoooh....sixteen-wheel drive! How many differentials does that require?


Just one diff...but the traction control is a wiring nightmare and I have to run 16 rotors, 8 master cylinders, 4 bias knobs, and 8 e-brake cables. I'm a little worried about the unsprung weight.

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PostPosted: Wed Dec 03, 2008 11:50 pm 
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A frame has, of course, a much more important function... but that is one good lookin' frame aesthetically.
.

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PostPosted: Thu Dec 04, 2008 12:14 am 
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I went through the build log and didn't see mention of what "size" frame your car resembles (i.e. +4, +442, etc.)....
.

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