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Building a Dio Tipo/Alfa Romeo.
Already have the body along with the entire drive-train and suspension so this should be a "Simple" build.
I've been debating using the TR4 frame I have or building a new chassis.
The body was originally designed around the TR frame so the track and wheelbase are correct.
The simplest build in many ways but still a cart sprung - lever shock early 50's design at the rear.

I also have the Art Morrison custom space-frame drawings that were commissioned for it.
Intended for Mustang II front and four-link rear, I think it's pretty similar to their old Cobra chassis and it's been used for high HP engines.
The AM drawing uses surprisingly little triangulation but that is easily added.
I will be modifying the AM design anyway to use as many original Alfa components as possible.
Not quiet as light but much simpler to service and for others to follow the same path.

The major flaw of the AM drawings is that they have no call-out for tube thickness or cut length.
This will be about a 150 HP engine.
Round tube design.
Hoping to use ERW to keep cost down VS DOM.
1-5/8 OD main chassis rails, .065" or should they be a little heavier?
Could they be a little lighter?
Trying to build as light as is practical for a street/hill climb car.
Most of the chassis tubes are 1-1/2 OD, again, .065" or .049"?
Balance of tubes are 3/4" OD and are not really structural so much as providing support for the very light fiberglass body.
The 1-1/2 and 3/4" tubes will get a lot of bending, some of them into half-circles.
Will the heavier tube bend with less tendency to flatten?

Want to order steel ASAP.

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If I must be a one-man PC free zone, so be it!

Heavier tube is less likely to kink, still bending is happier using a tube or conduit bender. I bought a Greenlee for 3/4 that works like a champ with a 6 foot bar on it.

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Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

With just the Alfa engine I'm thinking I can skip the hassle of 1-5/8 tube, difficult to find and much more expensive than 1-1/2".
So just use the 1-1/2" .065 wall.
I have a HF pipe bender that worked fairly well on my GT6 chassis reinforcements.
It did tend to flatten the inside of bends a bit but no real kinks.
If I go into production I will be looking for a real tube bender.
With the main rails 91" long filling with sand may not be practical.

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If I must be a one-man PC free zone, so be it!

I would guess you'll have trouble getting good bends in 1.5" tubing with only .065 wall thickness. Thinner material kinks much more easily than thicker stuff.

Also, if you're needing to do full 180 degree bends you'll need a higher-dollar bender and dies. Plus, usually when big 180 degree bends are made they are on a smaller radius than cheaper dies will do.

Finally, I don't know Art Morrison practices, but usually folks who use bent tubes employ thicker walls for the ones that are bent. The bend weakens things, so you want to start out with it stronger than you need.

Just my 2 cents.

-Graveyard

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Aedifico ergo sum.

ERW is fine, no problems with it, but it has a lower yield so it can't take quite as much stress before it takes a permanent bend. You also need to make sure you are not getting 1010, it must be 1020 or 1025.

You may be able to get the DOM in more sizes and wall thicknesses. 1 5/8" tube is %25 stiffer than 1.5" tube.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

As an aside, I wonder if the AM drawing had no material callouts because it was only a general arrangement for fit check to the body - AM was expecting to do the chassis build.

I have done quite a number of bends on .065 x 1 1/2 exhaust tubing without problems, but using a tubing bender with tubing dies, not a pipe bender.

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Warren
Isuzu Pickup/SR20DE, +401 COLD frame
Build Log: viewtopic.php?f=35&t=11601

Bend radius are not specifically called out either.
I can take some from templates made from the inside of the body.
There will be 180º bends but the radius will not be so tight like a U-bend.
Also much shorter so sand-fill may be possible.
Also considering significant changes for more triangulation and less reliance on wide curves.
Main chassis fore - aft rails do not have sharp bends, 45º up for 8.0" the another 45º to level again.
The fun ones are the half hoop that are also angled 30º back.
If the HF bender cannot do it I may send the first set out but to control cost I will still have to make the check fixtures.
Some of this would be simpler with square tube but I recall round being stronger and certainly easier for me to bend, as well as just looking better.

ERW I have a quote on is A513, if that's not good to use I need to look for another source.

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If I must be a one-man PC free zone, so be it!

For 1 1/2, I have great success with my home build Affordable tube bender knockoff. I bought the 90 degree die from ebay for about $100 and change and built the bender from stuff laying about the garage.
The jack is borrowed from the Horrible Fright pipe bender.



I used it again this past weekend making headers for the CBR600 motor.


No flattening of the 1 1/2 x .065 at all.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

You may need to do some searching, I found this quickly but it doesn't completely answer the question of what you are getting. It may tell you enough to know what to ask for though.

I think from previous talk here that ASTM 513 is not an alloy specification, it has to do with sizes, tolerances, radius on square tube corners etc. In the link above they include Chrome moly tube as ASTM 513. They do seem more specific about "ASTM 513 Type 5" which is DOM. In the table in that link you can see some pretty big differences in the yield strength of these materials.

If you go for the the ASTM 513 Type 1 or Type 2, these are 1010 alloy ERW hot rolled or cold, you only get half the strength - so cutting down on wall thickness would be a real problem - I think.

See the section on "mechanical tubing":
http://www.industrialtube.com/client/images/Tubing-Quick-Guide-Carbon-and-Alloy-Tubing.pdf

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

The smoothness of the bend with thinner walled tubes may also have to do with the grade of steel.

I had a slight wrinkling of the inside of the bend with .095 wall 1 3/4" tubing. I was using basically the same dies as the affordable bender uses. I have the Speedway Motors bender. You couldn't really see the wrinkles (more of a waviness), but you could feel them with your hand. These benders won't do more than a 90 degree bend, and sometimes won't even get that. The dies are generally for a 7" radius. To get a smaller radius you need more-expensive dies and a more-expensive bender.

I had completely smooth bends with .120 wall 1 3/4" tubing in the same bender.

I also bent some 1.5" tubing, and it bent smoothly at .104 wall. I didn't try thinner.

Anyway, it might be good to experiment with the specific material in the specific bender you intend to use before you make plans.

-Graveyard

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Aedifico ergo sum.

I think I've given up on .065 wall for the large diameter structural tubes.
Street car in Nevada, some of our roads are not so good.
Even with somewhat heavier tube I expect to cut the weight over stock by at least a third, but trying for half.
The body is really very light, it's a reproduction vintage sports racer body. Originally the Ambro Special.

So far the 2D cad and setting parts up on the build table are going VERY well.
Almost like this is the drive-train the fates intended this body to go on.
So I must be making a major error somewhere.

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If I must be a one-man PC free zone, so be it!

I have a JD2 Model 3 bender and they specify the minimum wall thickness for each die based on diameter and bend radius. Maybe this info will aid in determining what your bend capabilities might be.

https://www.jd2.com/p-44-m3-round-die-sets.aspx

Also, SCCA and NASA rule books generally specify 1-1/2" and 1-3/4" tubing, while NHRA uses 1-5/8" tubing. If you need to "out-source" the bending, maybe look for a fabrication shop locally that specializes in doing work for one of those series.

Just a thought.....

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Dan Lipperini Jr
www.RaceLabz.com

Could not stand it any longer and had some "Extra" money in hand, so I bought some 1-5/8 x .083 wall Cro-Mo at Summit Racing today.
The Sparks warehouse is a frequent stop for me, and I had to go to Reno anyway.
For the first set I will probably have a local guy do the bends.
But the bender linked above is not terribly expensive so if I do end up going into some sort of production I will buy my own.
Trying to locate a sample AM chassis to take some measurements from.
Know of one, but it's in OK and I am in NV.
If it is the nearest available I may be taking a fairly long trip this summer.

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If I must be a one-man PC free zone, so be it!

After doing some reading I am reminded that this is not really a "Space-Frame", but is actually a "Multi-Tube" chassis.
It is similar to several Cobra chassis, mainly made of large diameter 1.5" tube with little actual triangulation.
The same design has proven perfectly capable of handling 500 HP V8's.
So I'm sure that even if my tube is a little thinner 125 or so HP is not going to overstress it.
Alfa front arms and a four-link rear.
Trying for very neutral handling.

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If I must be a one-man PC free zone, so be it!

I looked on artmorrison.com and didn't see anything like this among their chassis, and I'm having trouble envisioning it from the description. Could you give us a pic of the drawings? Not with dimensions and details; I don't want to copy it, I just want to know what the heck you're talking about, concept-wise.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles