Mounting the Rear Sprocket

Mounted

Rear sprocket mounted on the differential

The limited-slip differential is a torsen or quaife type made by OBX, imported from the USA for an American-style Honda Civic. The differential ring gear on American Honda Civics is mounted with left-hand threaded bolts, so I blithely go down to the auto recycler here in Thailand and buy a differential for donor parts. Hmmmm… these bolts don’t fit. So I check carefully and find these differentials are sold in Thailand with right-hand threads! I go back to the auto recycler and ask for left-hand threaded bolts. They just look at me with that “crazy foreigner” look. OK, all we have to do is order some American-style bolts from Ebay US… There is exactly one listing on all of Ebay, and they don’t ship to Thailand! Plan B: drill the suckers out and use through-bolts.

This is where I find out the differential housing is made of some ultra-hard tool steel, or maybe kryptonite or something. Wow, are these holes difficult to drill out. Solid carbide end mill, highest speed on the milling machine, lots of lubrication, and wait. And wait. And wait…

Next we had to drill a matching hole pattern in the rear sprocket, then cut it in two halves for quick changing at the track. This sprocket will be for static test only as the new hole pattern wasn’t compatible with the old one, leaving thin aluminum in some places. I’ve since ordered a blank rear sprocket from England which I will cut with only the correct holes.

Turning the Steering Rack Extensions

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…

More Laser-Cut Parts and Panels

Laser Cut

Second batch of laser-cut parts.

I received my second batch of laser-cut parts, this time from a new supplier that has some more reasonable aluminum. They did a reasonable job, but man were they slow. It took three visits and more than two weeks to get a quotation, then I forget how long to do the work. Then when they were finished, I had to call them to find out. This is Thailand.

The parts are cut from both steel and aluminum of several different thicknesses, and include the radiator and oil cooler mounts, differential mounts, some engine mounts, the entire pedal cluster, parts of the steering column, chain tensioner, nose mounts, steering rack mounts, steering column mounts, lap belt mounts, chassis side panels, seat panels, the firewall, fuel tank, and even an idler sprocket.

Laser Cut Panels

Laser-cut panels including sides, seat and fuel tank

Anodizing and Plating Success

Found a supplier of anodizing and plating services up in Chonburi called Thai Silvec. I kind of got the impression they’d never had someone just walk in the front door with parts that needed plating and anodizing, but they accommodated me just fine. Very serious Japanese management, everything organized and clean, and reasonable prices. They gave me a detailed quality report when they delivered the parts, so now I know just how much allowance to leave for plating a mating parts. For next time, that is. This time around, I’ve had to do a lot of hand work to get everything to fit due to the stack-up of plating and anodizing thicknesses. At least I had them mask the wheel bearing bores, so the bearings later pressed in smoothly.

First Laser-Cut Parts

Below is our proof-of-concept for laser cutting parts in Thailand. Choices of material are extremely limited– ya got yer steel, see, and ya got yer aluminum. Unfortunately the aluminum is 1100, which has the structural strength of mozzarella, so I had to provide my own 6061-T6 to be cut. That didn’t reduce the price much, though. Redesigned some parts to match the available steel, which luckily is considerably stronger than cheese. I don’t yet have a sheet metal bender or supplier, so some parts have a slot cut where they are bent by hand and welded to shape as seen in the last photographs.

First CNC Parts, Class Photos

Uprights

Suspension uprights, two left, two right

Getting caught up on my blogging…

Shiny Happy CNC Parts

I’m getting some interest in the car from here in Thailand, but they want it SOON. So I’ve had to step up the rate of progress, even though it hasn’t showed here on the blog. Instead, I’ve been designing and designing and designing… It’s a big step from an assembly design that seems pretty much correct, to a set of drawings and IGES or DXF files that you’re willing to pay real money to fabricate. Everything has to be checked, from the load cases used in the finite element analysis to the hole clearances for every bolt.

For example, did you know that a 1/4″ bolt doesn’t go into a 1/4″ hole? The proper size of the hole is 0.257″ for a close fit or 0.266″ for a free fit. Of course, then you have to take into account the width, or kerf, of the laser beam used to cut the metal, which can be 0.01″ or 0.25mm but varies with the type of material and thickness being cut, and the laser beam is actually a cone that can be focused on the top, middle, or bottom surface of the piece. Many parts had to be redesigned for the materials and processes I’ve been able to locate in Thailand. Here it’s not a simple matter of looking up all the local suppliers on Google and giving one a call. Thailand has a great number of very small companies that rarely have websites, and even if they exist they’re mostly in Thai, which as a special favor to web search engines uses no spaces between words. Yes, you read that right. Using no spaces would be OK if there were only one way to parse a stream of Thai characters, but haha, you make joke, eh? And then if I can actually get someone on the phone, I have to communicate in Thai. Like that’ll work.

Last year I was looking for a foundry to cast aluminum uprights, and I found one (using Startpage, not Google) less than an hour from here. Their website had a Google map and everything! So I drive there, and I’m within 100 feet or so, asking motorcycle taxi drivers where the company is. No idea; there’s never been a foundry around there. I show them the address and they say oh, that’s way over on the other side of town. The person answering the phone number has no idea what I’m talking about. I give up.

On the other hand, recently one of those Google ads that look like the first links on your search actually showed me something that I needed and couldn’t find with a search: a small local company that fabricates custom radiators. So I managed to find their shop this week and got a quote for the radiator. Quote comes by email entirely in Thai. Google translate does a pitiful job of translating Thai, but I caught on the email wasn’t spam. Fantastic price, by the way. Cheaper than what I paid for a used race car radiator on EBay. I decided I didn’t really like how that one would fit, so I designed one that’s ideal for my application and figured I’d worry about fabrication later. Problem solved, yay!

The Thai racers who are interested in the project have emphasized that the price is crucial, which means more redesign. Surprisingly for me, this is the same thing I’ve heard from the people in Singapore who’ve contacted me. Sometimes it’s easy to dash off a quick machined aluminum design, but it takes a lot more thinking to do it with laser-cut steel pieces. The equivalent in steel typically ends up being a little heavier, but that’s an example of why Formula 1000 has a minimum weight rule. Laser-cut steel hand-welded into a complex component is just about free in Thailand.

Where before I was planning on making just about everything in my machine shop, now I’m looking at fabricating as much as possible at subcontractors. Luckily a friend found a large CNC machine shop not too far from here, and the guy running it speaks English and understands drawings and computer files and tolerances and clearances and everything. I’ve now received my first batch of CNC machined parts from them and they look great. Combined with the first batch of laser-cut parts and a few parts I’ll fabricate and modify myself, I now have everything to make the car a roller.

Anyway, on to today’s gallery:

Fabricating the Suspension Attachment Points

Hot Off the (3D) Press: Suspension Upright 3-D Print

The suspension uprights have gone through a long evolution, but I’m zeroing in on the goal.

First Design: Machined Billet Aluminum

This design uses radial-style brake caliper mounting. Needed to be redesigned when someone ordered the lug-mount calipers and had them delivered all the way from the USA. Probably a Freudian slip as they’re less expensive.

Machined Upright

Second Design: Fabricated Steel

Fabricated Upright

Second design was fabricated from steel. Unfortunately, welding will eliminate the temper in the heat-affected zones. The weakening due to this is hard to predict, and can only be eliminated by heat treatment. That would mean days or weeks finding and learning to deal with a heat-treatment supplier.

Mesh Quality

Mesh used for finite-element analysis of fabricated steel upright.

Upright FEA

Finite-element analysis stress plot for fabricated upright. Strong enough, but where are those heat-affected zones?

 

 

Third Design: Cast Aluminum

Here’s the final result of literally hundreds of design revisions, ensuring that the upright is strong enough and as light as possible. This design is made possible by the new technology of 3d printing, which will be used to make the master “plug”, from which molds will be made to cast the actual part. Note that the steering arm is not an integral part of the upright, but is modeled together with the upright because the FEA runs much faster this way.

FEA mesh plot for cast upright

FEA stress plot inner

Cast Upright FEA

View from outside

Finally, the Master Copy

The upright had to be split into four pieces for 3D printing; split vertically so I can make two mold halves and remove the masters from the molds, and split horizontally to fit the 3D printer. The 3D printer extrudes hot ABS plastic in X-Y layers onto a heated Z-axis stage with 0.3mm resolution. The print is slightly rough and the parting plane is slightly warped, which will have to be corrected with auto body putty, primer, sanding, and paint. The cast aluminum blank will still require several machining steps to cut off the gate and sprue, drill mounting holes, bore the bearing hole and retaining ring slot, and mill the brake caliper mounts. Still far better than trying to machine individual parts (or even a mold pattern) this complex, which would be approximately impossible and semi-infinitely expensive.

Beautiful, huh?

One half printed in two colors to highlight the split required to fit it into the 3d printer

Set of 4

Full set of four 3d prints. The cylinder protruding in the upper left is the gate, where molten aluminum will be poured into the finished mold.

Top View

Some people get excited by shoe sales. I get excited by this!

 

 

Fabricating Lower Suspension Clevis Spacers & Washers

Need some spacers to keep the clevises from interfering with some of the frame tubes. Also, custom load-spreading washers that my FEA says are important: