Building a Workshop Gantry Crane

Posted by jjludemann on February 22, 2014

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.

: Here’s what the overhead beam looked like when I started.

: Drilling holes to mount the wheels. Milling machine makes this easy.

: Welding the uprights to the wheel supports

: Thick steel is so much easier to weld.

: Welding the uprights to the overhead beam, upside down. C-channel is temporary, so it doesn’t fall over.

: Finished. Trolley and chain hoist bought at Hardware House, Rayong.

: So easy, even our spokesmodel can do it.

: Test lifting the chassis. Easy!

: Building adapter to lift the engine.

: First lift of the engine.

: While we’re building tools, here’s a holder to mount the angle grinder on the lathe.

: Parting off has always been a problem. Not anymore. Plastic is to keep abrasive off lathe.

Steering Column Supports

Posted by jjludemann on February 22, 2014

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.

: Front bushing; sheet metal cut on bandsaw and with die grinder

: Front bushing support bent to shape

: Front bushing support cap, ready to weld

: Finished front bushing support

: Turning steering column rear bearing cup

: Finished rear bearing cup

: Finished rear column support parts

: Steel insert bushing to prevent distortion of the bearing cup during welding

: Rear support, ready for welding. Note steel insert to prevent distortion.

: Test fit; fit was perfect first try.

: Rear support welded

: Ready to tack weld in place

: Tack welded

: Quality Control Inspector gives her approval.

Fabricating the Steering Column

Posted by jjludemann on February 22, 2014

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.

: Parts turned on lathe, purchased, and laser cut

: Front bushing and adapter

: Finite Element Analysis (FEA) mesh of collapsible steering column joint in frontal impact

: Finite Element Analysis (FEA) of collapsible steering column joint under maximum torque

: Finite Element Analysis (FEA) of collapsible steering column joint in frontal impact

: Collapsible column takes shape. 1mm steel is strong in torsion, weak out of plane.

: Collapsible section finished

: Finite Element Analysis (FEA) mesh of steering column quick-release adapter to column.

: Finite Element Analysis (FEA) of steering column quick-release adapter to column.

: Turning the adapter from column to quick-release

: Finished adapter from column to steering wheel quick-release

: Parts finished, still need welding

: Welded double U-joint. Note clocking of joints. Important!

: Welding the U-joints. Kept cool with wet cloths.

: Machining the steering wheel to fit the quick-release.

: Steering wheel attached

: Column finished

Fabricating the Seat Bottom

Posted by jjludemann on February 2, 2014

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.

: First two pieces clamped in place and ready to tack weld

: Finished welding, ready to attach to frame

: Bottom view showing attachment to frame

Fabricating the Lower A-arms

Posted by jjludemann on June 16, 2012

No, I haven’t just been sitting around the house eating chocolate, but a major malfunction in my main computer leaves me time to update the blog and get caught up on other things I should have done, like taxes. Unlike EVERY OTHER COUNTRY IN THE WORLD (except the Phillipines), even though I haven’t set foot in the USA in over four years, I still have to pay US taxes. The bright side is that California no longer considers me a resident so I don’t have to pay California taxes anymore, which is quite reasonable given that I moved out 11 years ago.

I made the mistake of turning the computer off overnight to help save the planet and all, and the next day it kept dying like someone pulled the plug. Computer shop says I need a new motherboard and graphics card, and oh, by the way, there are no new LGA 1366 motherboards for Intel i7 CPUs in Thailand and the old one will take about a month to fix under warranty. Which is understandable, given that Intel stopped making LGA 1366 i7 CPUs ages ago! Oh wait, they still make them? Or maybe not, from Intel’s website I can’t tell. At least Gigabyte’s warranty will cover their product, or maybe I just haven’t heard what their fine-print objection will be, yet. Azus, on the other hand, says my graphics card is corroded, and corrosion isn’t covered under warranty. Great plan! Make a product that corrodes, then say corrosion isn’t covered. It might be more honest to say “No Warranty”, though. The Azus graphics card was inside a warm computer (which was _almost_ never power-cycled) in an office environment for it’s entire life. Azus is now on my Deferred Vendor List.

Anyway, on to fabricating the lower A-arms, or control arms:

Repeat everything four times. Final result: four lower A-arms

: Starting with the spherical bearing cups, face and cut outside diameter

: Cutting the internal diameter on a bearing cup. This is a press fit, so it has to be cut as perfectly as the tools will allow.

: My boring bar won’t fit into my new quick-change tool holder, so I had to cut it down to fit.

: Boring bar now fits into tool block.

: Cutting the groove for a snap ring. I wasn’t sure I could get the press fit perfect, so I included provisions for a snap ring

: Snap ring in place for a trial fit.

: Using the cutoff tool to cut the part off the stock

: Bearing cup, spherical bearing, snap ring, and ID gauge for cup. I don’t have an internal micrometer, so used my external micrometer to cut a gauge to the precise length for the ID.

: I ground a carbide cutting tool for the boring bar to the correct width to cut the snap ring groove. It took a lot of grinding. Carbide is really hard!

: Starting the rod end receptacles that will be welded to the legs of the A-arms. Face and cut OD on lathe.

: Cut step to fit inside A-arm tube.

: Use center drill for accuracy.

: Drill hole to be tapped for rod end

: Using cutoff tool to part off

: Tap for 3/8-24 left hand threads. A later version of the A-arms may have easy rod-end adjusters, so I’m using left hand threads here, too.

: Cutting a chamfer on the face of the rod-end receptacle. Looks better, is lighter.

: Four finished rod-end receptacles

: Setup for tack welding rod end receptacle into A-arm tube

: Tack welded in place

: Welded all the way around. Holding the tube in a V block makes it easy to turn while welding

: Made 2 aluminum bushings to fit inside the bearing cup and locate it on the jig

: Rod ends are held in jig for welding.

: A-arm jig is made from printed drawing glued to plywood.

: Spherical bearing cup fully welded to one leg of an A-arm

: Both legs of an A-arm fully welded to a bearing cup

: A-arm bearing cup braces marked and cut

: Bearing cup braces in place and welded

: Pushrod mount in place and welded. These pieces were made with the patented (not patented!) technique of printing on sticker paper, cutting with a plasma cutter, grinding to exact shape.

: Spherical bearing is pressed into place on my home made hydraulic press. Custom bushings were made to only push on the correct places, like not the ball.

: Anti-intrusion bar test fitted

: Anti-intrusion bar fully welded. Weld shrinkage is a problem here.

: Welding distorted the bearing cap enough that I had to recut the bore. First, find the center of the hole.

: Next, use a boring head to cut the hole to exact dimension. Very tricky; had to use 1/2 the smallest tick mark on the boring head. Total overlap for press fit is around 0.001″

: Repeat everything four times. Final result: four lower A-arms

Building a Simple Hydraulic Press

Posted by jjludemann on June 16, 2012

I’ll be needing a press to insert the spherical bearings into the control arms and to insert the wheel bearings into the suspension uprights, so I took a couple of hours and built a simple hydraulic press. It’s just a strong steel frame that will give a small 5-ton hydraulic car jack something to push against. It’s taller than it is wide to be able to press items of different sizes by turning the frame on its’ side. Regarding painting, I’m finding that, with modern paints, I don’t need to use primer. I just clean the metal with a wire brush on a variable-speed angle grinder, clean it again with acetone and paper towels, then spray the topcoat on directly. This gives a thin, hard coat that sticks well.

: 4 x 2 x 1/4″ C-channel steel marked for cutting with the plasma cutter

: Plasma cutter makes short work of cutting this thick steel. Each cut would take more than 1/2 hour on a 12″ abrasive cutoff saw, but takes just seconds with the plasma cutter.

: Jigged and clamped, ready for welding

: After welding

: After painting

: Crushed a few things to test it. Can exert some pretty good force.

Building the Frame: Roll Hoop to Tail

Posted by jjludemann on March 8, 2012

: Removed the chassis from the jigs for the first time. Welded the bottoms of all the joints, which brought the chassis back to true & flat

: It’s a commuter car! You can carry it like a briefcase.

: Test fitting the rear beltline tubes. Chassis table has pins to locate these tubes, too.

: Rear subframe beltline welded…

: And into place.

: First parts back from the machinists’. Rear keel jig and the keel itself. Beautiful and accurate! Thanks, Somkuan!

: Rear keel, ready for welding.

: …and welded.

: Welded rear keel jig. Really starting to get the hang of this welding stuff. Yay!

: Bottom perimeter of the engine compartment fabbed and welded.

: Finished rear keel and rear keel jig.

: Engine compartment left side lower tubes

: Engine compartment right lower diagonal

: Bulkhead H right vertical lower tube

: Another example of how my Solidworks fishmouthed tubes fit, this one at the front end of the rear keel.

: Lower diagonal tubes holding the front of the rear keel.

: H-J inner upper diagonal tubes securing the front of the rear keel.

: H-J bottom perimeter tubes in place. These 3 tubes were welded flat on the table then lifted into place. Here you see the bottom of the car start to curve upward to clear the diffuser.

: H-J side diagonals. Here we work our way from front to back to avoid cutting off the ends of the tubes to fit them in from the side.

: J left and right lower verticals

: J to L left and right lower diagonals

: Released from the chassis table again to weld the bottom of all the joints. It’s so much easier this way I don’t even try to weld upside-down anymore.

: J-K inner bottom diagonals hold the rear of the rear keel

: K-L diagonals secure the rear of the rear keel to the beltline. This is the back end of the frame.

: Top frame rails from the main roll hoop to the back of the car are finally in place. Now we can see the complete outline of the frame.

: G-H upper diagonals are curved outwards to allow us to remove the engine from the top. The curve must be in the correct plane.

: From this angle you can see the curve. Removing the engine from the top is a design change based on feedback from the ApexSpeed.com forum. Top rail will be made removable later.

: H bulkhead, upper left vertical. Note that it’s not really vertical, but leans forward and inward.

: Test fitting the G-J upper diagonals. Sometimes it’s necessary to fit a bunch of tubes before welding any in place.

: Now we start welding them in place from front to rear. These are the G-H upper diagonals.

: H, H-J, J upper tubes (6). Skipped a couple of photos…

: It’s almost done. Just a few inner diagonals left.

: J bulkhead, inner diagonal UL-LR. This area of the frame is extremely strong as it has to support the suspension rockers and engine mounts.

: J bulkhead inner diagonals, LL-UR, 2 pieces

: H-J inner diagonals support the rear engine mounts.

Building the Chassis Jigs

Posted by jjludemann on November 25, 2011

First "professional" jigs

Because this looked like a lot of busy work, my first thought was to have the chassis jigs built by a local machine shop. So I bought the metal and had it sent directly to the machine shop and went over the drawings with them. They kept asking me how big various things were, when the dimensions were clearly right there on the drawing. Then it became clear they didn’t know how to deal with dimensions in meters. They asked me how to convert a dimension from meters to centimeters. “You mean like move the decimal point two places to the right?”, I’m thinking… This was not looking promising. Eventually I went home and tried to come up with a set of orthographic-projection drawings, with hidden lines removed, that they couldn’t possibly misinterpret. I soon gave up. When I went to pick up the first two jigs the next day, the list of errors was long and creative. Mounting footprint on one reversed, vertical tube holders cut too shallow and not in line, overall height incorrect, horizontal alignment out of spec, etc., etc.

Sigh. I called a local aerospace-engineer type that I know and asked him if he knew a good machinist, and he directed me to a local guy who I visited the next day. We met a couple of times and he is indeed capable of handling the project; in fact, I decided it’s really below his capabilities and ended up building the jigs myself, saving him for building actual car parts.

Lots of cut pieces waiting for welding, drilling, & milling

I needed a good, strong right angle to hold the pieces in place while welding. The bandsaw table served perfectly.

Welding the angles onto the uprights. Chassis table is very useful here.

Drilling the chassis table crossmembers on the milling machine.

First trial fitting of the chassis jigs onto the chassis table. Top rail guides not yet cut; other tube guides not yet in place.

Welding tube guides for vertical tubes. Sample tube keeps things in alignment, along with very careful tack welding.

Almost-finished complete set of chassis jigs

Chassis table crossmembers were drilled for pins to hold front subframe during welding.

3/8" bolts should be tight. But not this tight.

World’s First TIG-Welded, Finite-Element Analyzed Swing Set?

Posted by jjludemann on October 3, 2011

Although I originally learned to weld over 30 years ago in college when my team was building a Mini-Baja race car, I never did anything with it as one of the other team members picked it up faster than me and ended up doing all the welding. Welding has changed a great deal since then, so it’s time to relearn anyway. To that end I designed a swing set for my daughters, which I’m building with the same techniques I’ll use to build the Formula 1000 car, including the TIG welder, plasma cutter, tubing bender, and chassis jig table.

Initial build's fundamental resonant frequency

When I got the initial structure built I found it had a large side-to-side resonant frequency that I measured at 2.50 Hertz. It needed to be stiffened up. Rather than take a guess at how to fix it, with the possibility of several iterations, I decided to do what I should have done in the first place and perform a proper finite-element analysis.

I was pleased to find that the initial FEA results matched reality well, giving a predicted first oscillation mode frequency of 2.72 Hertz.

Then it was a simple matter of trying out a few modified designs and finding one that was functional, cheap, easy to build, and looked good. I tried several forms of bracing but settled on simply adding a slide to one side.

Addition of a slide increases natural frequency to 11.2 Hertz

A more elaborate version of the slide had been present in my initial design but had been discarded when I found out how slow I am at welding. The new design’s resonant frequency increased to 11.2 Hz, an increase of over 300%. Indeed, where the frame without the slide felt quite wobbly, with the slide it feels very rigid.

Learning to weld has been… interesting. Although I did find the appropriate pedal control for the TIG welder on Ebay in China, it turns out the pedal doesn’t work the same way as it does on an American-made welder. On a Lincoln TIG welder, for example, you use the front-panel controls to set both the minimum and maximum power and then the pedal moves within that range. On my Chinese welder, the current settings on the front panel are disabled by connecting the pedal and the pedal control range is always from zero to 200 Amps. Maybe this works OK for welding structural steel, but it’s not so wonderful for welding Coke cans. Or race car chassis, for that matter.

TIG welder settings for 1.2 mm mild steel tubing

So I had to take a step back, disconnect the pedal control, and through trial and error find a way to adapt the Chinese welder to my task. I spent some time poking around the Internet and learned a lot from this a most excellent thread on Race-Dezert.com, authored by one of the Gods of Fabrication. Based on some tips I gleaned from this thread, I switched to the smallest electrode (1 mm) and the smallest filler rod (1.6 mm) that I have. I turned the pulse rate way up to approximately the max of 300 Hertz, although it’s hard to say since there’s no readout, adjusted the pulse duty cycle to 50% and the “basic” current to 50%. At the higher pulse rate the digital readout gives an approximation of the average current instead of continuously changing semi-random numbers within the range like you see at the lower rates. When I nudged this averaged reading up from 60 to 65 Amps, things finally came together.

Finally, a proper weld!

I also bought a pair of cheap, strong reading glasses that I can wear under my welding helmet, and once I could see the process close-up and sharp I could make real welds! It turns out that the hot zone isn’t inherently fuzzy, it’s my eyes.

Apprentice welder at work

Quick Tour of the Machine Shop

Posted by jjludemann on September 9, 2011

I’ve been gathering the tools to build race cars since before I realized that was what I wanted to do. Before I finished building the house, I bought the really big machines at an open-air market in Bangkok and had them delivered through an opening in the machine shop wall that was later sealed up. Back then the truck could drive through the front fence and back right up to the front of the house, making delivery much easier. I’ve since lost track of the Bangkok open-air machine tool market, and would appreciate any info on how to find it again. Bangkok is a big place.