Monthly Archives: February 2014

Building a Workshop Gantry Crane

Posted by jjludemann on

I need to be able to lift the engine into the chassis, but due to the lowered floor of the work area a standard engine lift won’t work. While I’m at it, it would be nice to be able to lift the entire assembled car off the build table, turn it ninety degrees, move it to the door, and roll it out of the shop. Below is the solution. Sorry there aren’t any plans. The build process was “go to your local metal recycling center, buy some scrap beams, clean them up, cut them as necessary, and weld them together”. I’m getting more comfortable with winging it in the machine shop.

Also shown below is a mount I built to mount an angle grinder on the lathe. Parting-off has always been a problem. I’m just about to make the engine mounts, requiring at least 36 cutoff operations, and I figured I’d better solve the problem. I have a cutoff tool but only purchased a small number of carbide inserts; the inserts wear out really fast and I either have to order more from the US or drive at least an hour to a store that MIGHT have them. This baby works great, giving a clean straight cut. Just have to be careful not to let the abrasive get into the lathe.

Steering Column Supports

Posted by jjludemann on

Next up: mount the steering column in the chassis. Nothing magical here, just lots of little steps. The steel bearing cup insert did work well at preventing distortion during welding. To get a proper press fit for the rear support bearing I decided to use my new internal bore gauge. At first it didn’t work at all (made in China, of course), so I had to disassemble it completely, figure out how it was supposed to work, unstick the rusted shaft, replace the dead battery, and reassemble it. All in a day’s work out here on the frontier. So now I can measure both holes and shafts to a few microns and press fits are much easier to make.

Fabricating the Steering Column

Posted by jjludemann on

I originally sent all these parts out to the CNC shop, but they never got back to me with a quote so I ended up making everything myself. The spline onto the steering rack was a tight press fit, so for now the entire column including the rack is a single assembly. I don’t know it’s possible to remove the rack later, and I’m not going to try as it might destroy the rack. The U-joints are special units from Sweet Manufacturing in the US, but don’t seem to be anything special. In the future I might try to adapt standard Honda steering column U-joints and column splines. These use a perpendicular pinch bolt so the column can be disassembled at each joint.

Turning the Steering Rack Extensions

Posted by jjludemann on

The ends of the steering rack have to be in line with a plane through the control arm attachment points, and unless you have a custom-made rack this will require extensions to each end of the rack. I got these made and then went to the local nut & bolt emporium, only to find they don’t carry 3/8-24 socket-head cap screws. I know, weird huh? Had to order them on Ebay in the US and am now keeping my fingers crossed that they will arrive (at all). I recently ordered some more left-handed nuts the same way and they arrived in eight days with no problems, so yay?

For these I had to dig into my precious stash of 7075 aluminum…

Modifying the Wheel Hubs & Axles

Posted by jjludemann on

We’re using Honda Civic wheel hubs, wheel bearings, CV joints and axle halfshafts. They’re available everywhere, cheap, and light, and by using them we avoid having to cut matching pairs of splines. The wheel hubs are drilled for lightness and tapped to accept the wheel drive pins, then the two outermost pieces from two scrap CV joints are cut down to use as bearing retainers for the front wheels. Rear axle halfshafts are used in stock form, but extenders from the halfshafts to the differential will have to be fabricated later.

When cutting the CV joints I found that the contact faces are hardened some way into the joint, making cutting almost impossible (by which I mean “impossible”) beyond a certain point, even with carbide cutting tools. If they are heat-treated, maybe there’s some way to reverse the hardening? It’s probably something more exotic than that, though, as the hardening was highly location-specific.

Fabricating the Seat Bottom

Posted by jjludemann on

Just a quick update here as the next one will be big and I want to keep it together as one post. I want to get all the tabs and brackets attached to the frame as soon as possible so I can paint it, so I started with an easy one: the seat bottom. I had the pieces laser cut, but the shop forgot that there are two identical side pieces and I had to cut that one by hand. I turned out to be easy after making a paper template. Each of the four pieces is a section of a cylinder and some of the edges intersect off-axis with frame tubes, so those lines that look straight really aren’t. The seat bottom is curved like this to get the driver as low as possible, mainly to keep the top of the main roll hoop as low as possible. The curvature was easy to make by just bending the steel by hand and fitting it by eye to the frame.

Attachment points are carefully spaced more than six inches from each other to comply with the F1000 rule outlawing stressed panels (with certain exceptions). It would have been much easier to just weld each piece to the frame tubes below it, but I don’t plan on this counting as the stressed belly pan. A stressed belly pan will be added to the planar bottom of the car. Making the seat bottom removable gives the advantage of easier access to the triangular compartment below it for mounting the fire extinguisher and whatever else will fit, and I can also replace the seat bottom later with a carbon fiber and kevlar version to save weight. At the moment I’m appreciating the fact that certain important body parts will be protected by two layers of steel in the event of a crash.