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Learning how to build Lotus Seven replicas...together!
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PostPosted: October 21, 2017, 2:14 pm 
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RichardSIA wrote:
Ah, thanks?
These are structural bends.


Oh! And here I thought that you were using a cut off wheel and a welder for every other structural joint in the frame. Must be my mistake!! :roll:

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PostPosted: October 21, 2017, 2:23 pm 
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Seriously?
No, I do not stack welds edge to edge for several inches creating more filler than base metal.
And the grinding!

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PostPosted: October 22, 2017, 11:30 pm 
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A'Ha. :!:
I was having some trouble figuring out the radius for the bulkhead corners.
No spec on the drawings.
So tonight I put a projector lamp on the drawing and a large piece of paper on the wall.
Then traced the image.
From this I was able to determine that the inside radius appears to be a pretty standard 6.5" for 1.5" tube.
Which makes the outside 8.0".
This seems to make sense as larger dies would be even more expensive.

Then I measured the body edge to edge at 59.5".
Chassis outside is 54.5".
So now I know that the body does not follow the chassis contour exactly.
That may be good as it gives me some leeway for the actual body mounts.
I want to use Dzus fasteners so the body is easy to remove any time I need to work on the mechanicals.
Some squeeks will not bother me and probably cannot be heard over the exhaust anyway. :D

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PostPosted: October 31, 2017, 2:16 am 
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Quote:
From this I was able to determine that the inside radius appears to be a pretty standard 6.5" for 1.5" tube.
Which makes the outside 8.0".
This seems to make sense as larger dies would be even more expensive.


Well, :shock: :BH: :ack: !
Decided that for what having bends done was going to cost I may as well bite the bullet and buy my own bender, which I did.
Got a fairly good deal on a JD2-M3 with 3/4, 7/8, and 1.0" dies plus a stand.
But after watching some video I now realize that the die radius is measured to the center of the tube, not the bottom!
So what I most need are actually 1.5" x 7.5"R!!!!!!!!!!
Just about the most expensive size possible, $430 new as I recall.
Anyone have decent discount code or other cost savings for me?
Set I can RENT?
Need to do fewer than twenty bends in 1.5" CroMo.
Cost of dies is killing the material budget. :BH:
Outside radius is not actually an exact match to the body contour so 6.5"R would probably work fine.

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PostPosted: November 1, 2017, 12:41 am 
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:lol: Take your material budget, double it, and add 10%. $430 for the die will just be a fraction of the build cost.
You'll do fine. :cheers:

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PostPosted: November 1, 2017, 12:59 pm 
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Bought the :ack: expensive dies.
Did find a code that saved a whopping 5%. :roll:
Should be here in about ten days, then it will be time to fab some tools before the first real bends.

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PostPosted: November 13, 2017, 8:32 pm 
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Dies were delivered today. :!:
Now I have to decide how/where I am mounting the JD2 bender.
And buy some 1.5" CroMo.
May actually have something worth taking pics of soon.

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PostPosted: November 17, 2017, 10:46 pm 
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Finally found time to make my first 1.5" Dia. 90º bend of some scrap I had.
This will become a tool.
Turns out a 7.5" R. 90º bend consumes almost 12" of tube.
Hoping the actual .083 CroMo bends easier than this .095 DOM, but I expect I will be lucky if it's about the same.
May have to add some air assist if I can find the air-cylinder I have here somewhere.

Thinking now that making 90º bends and joining them will be much simpler than trying to get double 90º to come out exactly right several times.
At least for the first such build.

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PostPosted: November 18, 2017, 4:29 am 
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Sounds like it's going great so far! Keep in mind if you are going to track the car, most sanctioning bodies don't allow splices in the main hoop, must be one continuous piece.
Edit: Just as a psa, Miller has a pretty good piece on welding Chrome Moly tubing on their website. Here's the link. https://www.millerwelds.com/resources/a ... plications
Happy Welding!

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PostPosted: November 18, 2017, 2:53 pm 
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With this chassis design there really are no continuous hoops from side to side as the hoops at the sides end at the main fore-aft frame rails.
Then they continue to the other side as they tie in with simple strait tubes across the chassis.
I do plan a single seat type roll-hoop but since it's a single entity no worry over duplicating it.
I will be adding several diagonals to the original design.
With only about 130 HP and fairly narrow tires this chassis will be very overbuilt.
It's original design is claimed to be good for 500 HP and very wide tires.

Once this car is built I want to do more to sell, on Miata running gear and a true space-frame.
No real desire to build a fire-breathing V8 monster for myself using this body, I have a '68 El Camino for that. :chev:

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PostPosted: December 13, 2017, 5:49 pm 
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Ah ha, found THE source for steel!

http://www.aedmotorsport.com/catalog/pr ... round-tube

Just paid $3.83 Ft. for US MADE 1.5" .083 Chromoly.
Cut from 17'-3" to 8' lengths plus the drop for UPS shipping.
Compare to $6.23 Ft. at Stock Car Steel, or $6.60 Ft. at Aircraft Spruce!
Even with UPS shipping of $101.00 I'm getting eight 8 Ft. pieces for only $366.00
And the short drops for welding practice, reinforcement, etc.

I saved at least $150.00 over other sources.
These guys have 60,000 feet of Chromoly in stock at any useful size.

No affiliation and all that, just REALLY happy with the price. :D
And only four days for delivery! :shock:

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PostPosted: December 26, 2017, 5:25 am 
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After tonights workout I now know why most guys are using strait sections of square tube.
Bending 1.5" Chromemoly is a lot like WORK.
I will probably be a bit sore in the morning but I now have the bends done for my rear main hoop. :)
Forward hoop should be simpler since the sections are shorter.
Then I get to begin making the chassis an actual 3D structure, which will finally look like real progress. :D

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PostPosted: January 7, 2018, 4:10 am 
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Despite Flu and walking pneumonia I just HAD to make some progress on the Alfa-Dio today.
Got the rear hoop tacked into shape and the fish-mouths cut to join it to the main chassis rails.
Good to see it becoming genuinely 3D. :)
Hoping to bend some front hoops tomorrow.

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PostPosted: January 7, 2018, 11:15 pm 
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Ah well, I guess any bend that does not come out exactly correct is "Practice".
I'm having some issue getting exactly 90º and perfect spacing of hoops with an about 4" strait section between two 90º corners.
So I will have a couple more welds than ideal but this chassis is so overbuilt for my engine that it cannot really matter.
I am also tweaking the design a little for more strength.
This entire first build is "Practice". :roll:
Since it's a "Practice build" the hope is that I will be able to use that as an excuse to KEEP it when someone tries to buy it from me.
One more double bend and some fish mouthing then I can tack the front hoop on.
A few simple strait rails and the main cabin structure will be pretty much complete.
That will help a lot with finalizing engine placement.

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PostPosted: January 10, 2018, 5:50 am 
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OK, finally some progress worthy of pics. :D

Main lower rails and cockpit hoops are tacked together.
Have to clamp the chassis firmly to the table before I can do anymore actual welding.
There are several horizontal supports to be put in between the hoops but at least I am done with bending tubes for a while.
Once the rest of the cockpit tubes are in the chassis sould be stiff enough to hold it's shape and remain square.

Engine should be very close to it's final location, well behind the front axle centerline. :)
Axle center is at the rear edge of the middle band of green tape.

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