How to make Welding Jigs

[ssc0007]

It's my team's first year doing FSAE. While my school has a good combustion team, this is the first electric car at the university. When I asked my faculty advisor how we should weld our frame together he told us to make the verticals and hoops then set it up into jigs and weld the horizontals in. My question is what do you make your jigs out of and how do you make them? My thought was to just machine them and put slots in the metal(probably aluminum) and bolt them to our jig table. Am I thinking on the right path or not?

[Will M]

That sound like it would work, honestly it is more than we ever did for most of our frame.
I would recommend thinking about where you need accuracy (hint: suspension, engine, and drive train) and where a tape measure would be accurate enough.

We would fabricate the MRH, FRH, and the bulkhead separately and bolt them to our table (we would use small aluminum jigs).
An old engine was also then bolted to the table .
The majority of the horizontal tubes were added next.
Then install the jigs for suspension points, if everything checks out remove the frame and finish the rest of the tube welds.
Put the frame back on the table and bolt it into place, check the jigs for fit up again.
If they look good weld in the suspension pick up points.

Welding the suspension points in last lets the rest of the frame be different from the CAD model and it doesn't matter if it warps a little bit due to welding.

-William

[Jonny Rochester]

From photos, I have seen some teams go to great lengths to have a good accurate jig, to the extent of having CNC machined or water-jet cut components of the jig. (More money spent on the jig than the actual chassis - which can be justified over 1000 units!) Some of these nice setups start with an expensive T-slot table, and the jig peices themselves are designed in CAD.

For our team, we didn't think we had the money (or confidence to waste that amount of money) and we just started with a flat(ish) steel table that we already had.

We extended an existing metal table. The table top was our reference plan, which was also the bottom plan of the chassis. The plan of the lower rails was draw on the table. With the lower rail structure welded, we used scrap bits of metal and welded them to the bench to hold various chassis parts in place.

We can very easily use a MIG welder to just weld scrap metal to the bench. We can always cut it off later and grind it back.

Verticle alignment of the main hoop is eye-balled with a plumb bob.

A lot of stuff was eye-balled, and it is crooked! Does it matter? Time will tell.

[Mitchell]

(More money spent on the jig than the actual chassis - which can be justified over 1000 units!)

Some of the jig systems I see around are way over the top for a one off chassis. We use some old C channels that were welded together and face milled and some waterjet 2mm sheet steel for longitudinal and lateral jigs.

The only dimension that is realistically sensitive to manufacturing tolerances on an FSAE spaceframe is the vertical position of wishbone pickups. Even these can be positioned with a steel ruler. Get an old engine block (or use your good engine carefully) and the engine mounts will jig themselves. Design the chassis with fabrication and jigging in mind from the beginning. Find a tube notching sponsor and you can pump out an accurate spaceframe in a weekend of relaxed work.

This is our first design/build spaceframe. Tubes were laser notched, 2mm sheet waterjet longitudinal jigs, lateral located by a ruler!, suspension points were part of the SHS sections. As you can see all the flat sections were done first and dropped into the jigs. Total cost of chassis jigging was in the $40 range. The only measuring equipment used was a ruler and tape measure. This was an extremely (unnecessarily) complicated spaceframe and still only took a couple days of actual working time.
https://www.youtube.com/watch?v=qiJ32vCZ2qI

This is our second attempt. It was ~16 hours of working time. Similar process, but jig plates were longitudinal and lateral. Still under $100 for jigging. Shows a bit more of the engine jigging. This chassis had significantly less nodes so it was a pretty quick process.
https://www.youtube.com/watch?v=yhPzjggdpAs

Fabrication of a spaceframe is a great rewarding process - my personal favourite part of the car build.