Chassis for a Solar Car

Simple ladder chassis from tube?
Or a monocoque from plywood.
It depends on what you have lying around, what facilities you have and what skills you possess.

Del

Find some resources for aluminum. You need to keep it light. Look a bit harder, and I'm sure you will find someone who can fabricate aluminum.

plywood and fiberglass are good choices. What do you have available?

I have to admit that I have never welded aluminium and I know that its not the easiest of metals to weld, but surely it would pay you to go and take a course in Ali welding!!!

No rust and little conservation needed, plus light weight are sterling qualities needed in any vehicle....

I recently taught myself to MIG weld Stainless Steel in about an hour with no one to ask. The first two units I made were complete rubbish, the 3rd, 4th and 5th were perfect!!!! Practice makes perfect!!! It was nothing complicated, but it had to be very accurate - CNC linear drive nuts.

I am not trying to imply how great I am, just that when you have such a vested interest, you can learn to do anything!!

Do not pay for to have an employee learn as he will have you over a barrel with pay.....or make a contract with him first to cover YOUR ASS!!! At least two emplyees need the skill, one should be you in the begining!!!

If you look at the chassis on the Lotus Elise it is fabricated from aluminium but bonded together instead of welded. Morgans still use a wooden chassis on their classic cars made, I believe, from ash.

You could perhaps use a combination of materials, maybe a bonded aluminium frame skinned with glass fibre.

As mentioned earlier it all depends on your resources & available skill.

You can also solder aluminium (just like still with brass) but you must use a high silicon filler-rod that makes it melt before the parent metal as well as run better. The flux has to be the right type also. (This is the old method and the solder material is as tough as the parent one.)

There's also a new type of soldering material you can use to solder aluminium with and no flux required. (This supposed to be the new way and I only saw it at a show once where they used it on the bottom of a coke can, don't know about its toughness though.)

Both methods can be done with a gas torch with the right size tip or use the oxy aparatus.

I think the new method is Durafix EasyWeld. I've tried this & it produces a very strong joint but requires a lot of heat to be put into the materials being joined.

The amount of heat you mention is a well known problem with Aluminium, it soaks the heat away very, very fast......

Amateurs working on Ali with a torch, see areas near to where they are working just fold away........a hot torch and quick in and out are the rules of the day. (That was from watching many years ago, not doing!!)

I know what you mean. When I tried the Durafix I had 2 pieces of 50mm x 3mm angle about 25mm long so not much heat sinking. With Durafix you have to 'tin' the surfaces first with the alloy rods but it took a lot of heat before the alloy would wet to the surfaces.

If you have no welding experience in TIG aluminium I would not recommend you try it on a lightweight chassis it takes a lot of skill and carefully fit up.

It would probably be better to use square section with fillets and bolted or pop rivet joints with careful design it would not increase the weight that much.

Also thin wall steel tube can be nickle bronze welded if you wish the joints are as strong as the steel tube if you sketch out your design and do some weight calculations for the steel depending on your wall thicknesses they don't all have to be the same thickness depending on location and load to be carried, you might be surprised at the total weight.

Steel tube or wood frame with fabric covering is still quite popular for lightweight aircraft construction, and has been used for trolley car construction. With enough coats of a compatable paint system, the cloth becomes very stiff and weather resistant.

Although it is often said that aluminum is hard to weld, that is anything but true. (It's a little like saying wood is hard to join with bubble gum.) With the wrong equipment is is very difficult to make a good weld in aluminum, and the various brazing methods for aluminum are virtually worthless, in my view -- it is only worthwhile if you place no value on your time, and could care less about structural integrity or joint appearance.

TIG is a great tool for the job of welding aluminum, and with a little practice, you can produce excellent welds.

As you probably know, good quality aluminum bicycle frames are not substantially lighter than a good quality chrome moly frame. They are, however, lighter than a "gas pipe" (mild steel) frame. However, even a mild steel frame can be both light and stiff if the sections are large and thin wall: a monocoque structure is a very large section and very thin wall.

The vehicle in my avatar is a monocoque using thin plywood covered on both sides with thin fiberglass cloth in epoxy. This makes a remarkably light structure. In fact, this vehicle started out on two wheels, with the entire enclosed body weighing less that the frame and body parts from the much smaller motor scooter from which the mechanicals were stolen. The monocoque is at least ten times as stiff as the original scooter frame.

For simplicity, it would be hard to beat a rectangular perimeter frame made from 1/4" plywood square tubes of perhaps 4"x4" cross section. Provided these tubes are closed at the ends, the two longitudinals would provide both adequate torsional and bending stiffness. Locations of any through-bolts with significant load would need to have compression members (such as 1" dowel) bonded in (to prevent bolt compression load from deforming the square section). Subframes for suspension, motor mounts, etc. could be welded from steel tube and bolted to the main frame.

Look at old (mid sixties)Lotus Elan frame pics for ideas re using aluminum sheet bent, bonded, and riveted into a semi-monocoque.

Durafix Easyweld - Aluminium welding made easy!

I guess this is that stuff I was on about earlier but since it has been almost a decade when I saw it at an exhibition I forgot its name.

I do remember a very thin ALU can could be welded with it and as you can see a gas torch is all you need with this technique you may have slight heat distortion.

Of course I could have suggest the TIG method but you may not even have it since you do not have much experience, have you?

I would definitely avoid pop riveting since the more you drill the more fatigue you make the joints if you opt for using ALU profiles.

For cost exercise I think ALU is not you #1 choice hence you must consider something cheaper.

The simplest frame I can think of is a Ford Model T. Two slightly angled C-channels with two riveted cross members of sufficient width to resist racking. If done in the lightest aluminum extrusions necessary to support a load as light as 400# plus driver and amenities, and bolted together, it should work. If long term durability is an issue, heavy it up a bit.

That 181.8 Kilograms of weight for starters.

so at lease you would need about work area of about 234 by 48 in mm or cm. but these minimum parameters should should guide a solution for ya.