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Learning how to build Lotus Seven replicas...together!
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PostPosted: November 3, 2010, 8:19 pm 
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I have a feeling that after people see the pics of the tub you just posted that this is going to be a "must see" tread, keep up the good work, looks very very good .
Cheers, tony


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PostPosted: November 3, 2010, 8:51 pm 
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Thanks for posting a semi-monocoque design, we have questions about this sometimes but haven't had any examples. People are pretty fast at putting the space frames together, do you have a rough idea how much more or less labor will go into your center section? It doesn't seem to bad, it's all the little details finishing a car that seem to add up...

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PostPosted: November 3, 2010, 9:48 pm 
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Tony, Thanks for the encouragement!!
I realize others are nervous about an aluminum structure but I feel that with the thickness and alloy that I am using, I am ok. Unfortunately it is not as "locost" as I had anticipated. Aluminum so far is $350.00, rivets are $250.00 (I had some already!!), adhesive is $145.00 and use of shear & computer controlled press brake $140.00. I think tubing and thin aluminum shear panels are much more cost effective. In my favor - lower body (14" and below) is done at least between the subframes.

JMR

Horizenjob,
The biggest problem is accuracy of bends. I used to have access to a shear, a press brake and am comfortable with tight tolerances. I moved to Port Angeles, Wa. -- WOW -- A different world from Southern California. I talked to a local sheetmetal shop about bending the Al. His comment was that they worked in +/- a 1/16". This was not a good sign for me!! I finally found a very helpful shop that allowed me to do a lot of the work without their direct supervision. I held tolerances that the owner did not believe I could.
I tried to save on the number of rivets but it forced the tight tolerances because of making the sides with 2 bends each (forming a channel). If I had made as many of the panels with only one bend each, the tolerances and grief would have been less. The big thing now is fitting the bulkheads. The inner panel of the sponson is at about 6 deg and the outer is at 10 deg. In other words NOTHING is parallel! I have made 5 trips to the sheetmetal shop for shearing and braking (bending!!) alone.
To partially answer the question - alot of time and professional equipment is needed for a tub of THIS design. I probably have 50 hours of layout, fabrication and fitting to get where I am now, just in the aluminum tub/center section. However the seats will be done as part of this. Adjustability of the seats will be by moving foam pads around and/or adjusting the pedals.

I designed and built my CanAm car in the late 70's with inspiration from the McLaren M6/8 designs.
The front bulkhead is in a single plane with fore and aft suspension loads fed back into the tub. The lower control arms attached inside the driver area of the tub to the under knee panel. The tub ended at the roll bar with the engine stressed as part of the chassis. I bought a bellhousing (and front and rear hub carriers) from Dan Gurney's All American Racers that allowed bracing from the rollbar to be attached to it for torsional, vertical and horizontal loads. The rear suspension was attached directly to the Hewland LG500 transmission with radius rods going forward to the rollbar. The tub was also built with .065" 6061-T4 aluminum. The car is now in Sweden the last I heard.
The picture was taken of me at Riverside Raceway in the late 70's.


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PostPosted: November 3, 2010, 10:49 pm 
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That's interesting, I have a friend with an old Ralt, will have to look more carefully - I remembered it as fairly simple, but a close tolerance like that is not so visible unless you really think about putting it together.

Can-ams and ASR's got unaffordable pretty quickly, I guess. When I was young I would meet or talk with people that had run one, but I think I missed the fun stuff by just a few years. I didn't get on tracks much until the late 70's. The older guys ( must have been in their 20's but seemed older :D ) actually got to run against Mark Donahue and others in the trans am etc..

I've always been bummed, they had such fun before it cost so much and every car got covered in advertising. If they outlawed the advertising it might be fun again. Can probably date your car just from that, pre '75?

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PostPosted: November 3, 2010, 11:43 pm 
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Thanks for making us young'ins regret not even being around in "the good ole days" Marcus. ;)

Nice looking chassis JMR. It looks very well thought out.

How do you integrate the leg hoop into the moncoque structure? Just a plate to spread the load at an internal bulkhead?

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PostPosted: November 4, 2010, 2:46 am 
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I ran the ASR thru 1982 I believe - found an old trophy with a date. Ran the car in Regional and National SCCA races. Sold the car and built an airplane. Sold the airplane and built a Formula Vee. Sold the FV and raced a 125cc Honda shifter kart. Moved up to a 250cc Superkart that is now for sale. Now the MR2 based Middy. I love projects!!!

a.moore,
A steel plate will be bolted and riveted to the top of the tub for the front roll hoop and the connecting braces back to the main hoop. There will be an "X" brace from the front subframe to the front roll hoop that will also stiffen the front of the tub. The brace will be bolted to the front subframe and front hoop plates but 3 of the "triangles" will be filled in with Al sheet that is riveted and bonded. The front triangle will be made removable for access to the pedals and possibly a front mounted battery.

I am thinking to fabricate the front hoop, plates and rear braces as an assembly. I will install the plates to the top of the completed tub and THEN weld the braces to the main hoop. Another option would be a joint between the braces and rear hoop. I want something clean looking.

JMR

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My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6


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PostPosted: November 5, 2010, 4:46 pm 
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Kartracer47 wrote:
I have gotten a little further. A big HONEYDO got in the way.
I now have rivets (over 3000) and adhesive ( $140) to continue. Drilled a lot of holes!!
Thanks for the positive comments (surprised at how FEW I have gotten!!!!!!!). I will post more pics as I progress or maybe just leave the forum????

JMR

Those "honeydo's" are a pain eh? lol, Just umagine how many more projects we could have if it wasn't for the honeydos :wink:
Anyway, Mr. JMR, I realy like what you are doing, I'm envious of the aluminum tub, might have to have you build one for me :wink: .
See if you post some more pics and stop complaining about how many trips you have taken to do the bending, lol
:cheers: Tony


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PostPosted: November 8, 2010, 3:22 am 
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Eurocraft - way too much time in the tub to be a "pay job" unless you are related to Gates.

I got the weekend off from hoheydo's - PROGRESS.

Fitting the bulkheads, front roll hoop and forward braces. Many more holes and I am out of cleco's - more on order.
I lowered the forward braces at the rear roll hoop in order to see over them. If there is any static about their height to the top of the roll bar, I will add a small diagonal.
The tub assembly will be fun!! The best sequence is still being determined.


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My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6


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PostPosted: November 8, 2010, 4:06 pm 
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Looking good, keep up the good work.
:cheers: Tony


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PostPosted: November 29, 2010, 8:44 pm 
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Finally back on the project. A large honeydo got in the way. I enclosed a patio to create a 150 sqft "studio" for the wife and extended the roof for her golf car to park under.

I finished fitting the bulkheads to both sides. Next up was determining how to get wires, cables and such, front to back. PVC electrical conduit was the solution. Conduit strap clamps and aluminum brackets at the bulkhead pass thru's should well anchor the conduit and keep it from chaffing.

Positive battery cable will be in the lower right side and brake/clutch lines in the lower left side conduit. Lights and engine wiring in the upper conduits on both sides as needed.

Lastly the fitting of the outer skins!! MANY more rivet holes!! Ordered a 100 more cleco's from Aircraft Spruce.

Next up is interior details - seat divider, dash area, steering column mounts, etc.

JMR


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My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6


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PostPosted: November 29, 2010, 9:23 pm 
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Wow! Amazing build! It looks more like you're building a stealth bomber than a "home made" car! Love the unique construction. I almost said "unique monocoque" but that just sounded too intellectual for me to write... What type of rivets are you using? I'm going to be riveting an aluminum belly pan onto my steel chassis soon, need to use the "right stuff" (since we're talking aerospace). Any advice?

Keep up the good work!
:cheers:
JD Kemp

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PostPosted: November 29, 2010, 10:08 pm 
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I just really like what you've got going on there. For whatever reason your build excites me more than most.

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PostPosted: November 30, 2010, 4:11 am 
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GonzoRacer, I am using USM or Cherry BSPQ 4-2 thru 4-4 structural rivets. They pull like a standard pop rivet but the shank of the mandrel breaks at the head of the rivet. I ordered them from Aircraft Spruce. They cost from 12 to 14 cents apiece. http://www.aircraftspruce.com/catalog/h ... nrivet.php

Carguy123, I hope I can keep the excitement up myself!! Thanks!!

JMR

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My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6


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PostPosted: November 30, 2010, 8:19 am 
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Whats good for the home is not always good for a vehicle. The wires and cables will rub and vibrate against each other in the tube without clamping. Any dirt that gets into the tube will add to the friction. If one cable shorts, it can cause the others to short from the heat if the accessory requires significant current, because the fuse will require more amps before blowing. There is no way other than removing the bundle or cutting out the tube to inspect the rest of the wiring in the tube if you do have a problem with one wire.

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PostPosted: November 30, 2010, 9:13 am 
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JMR wrote:
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I am using USM or Cherry BSPQ 4-2 thru 4-4 structural rivets.


Aha! 8) Exactly the ones I've been looking at! Affirmation is a good thing.

Thank you for the concise, complete answer. :)

Wish ya continued good luck on your build.
:cheers:
JDK

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