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Discussion Starter · #1 ·
Several people have hinted that they want to know how to make aluminum chassis from 3/4 inch aluminum square tubing. My apologies in advance for the size of this thread. This is simply how I make them. I take no responsibility for anyone doing their own thing. Always keep safety in mind before performing any machine work (safety glasses, etc...).

I bought this Airfix static model for five dollars at a flea market last year.

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The paint is now two weeks old and safe to handle.

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The first step is to measure the body. Choose a motor and gears. True the tires to fit the car. Figure out where the guide and body posts and axles should go, etc...

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A local hardware store supplies the 3/4 inch square aluminum tubing (Home Depot). It measures 3/4 x 3/4 x 1/16 thick. Hiding somewhere in this material is a Triumph chassis. It's been marked and scribed for hole location.

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A good drill press, with a precision vise, on a compound table (precise XY axis movement absolutely required). Best speed is slow (600 rpm).

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I drill the body posts first. Tools required. 90 degree countersink. 0.121 inch clearance drill for a 4-40 screw. Number 2 pilot drill.

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A good machinist always uses a pilot drill first for a properly centered hole. It can also be used as a locator for pin point accuracy on the cross hairs. You can make a small dot and see how accurate you really are. If you are off a little off, you can make a correction and the drill bit won't wander because of the large shank. Plunge the pilot when it's spot on. No oil required for the pilot drill through aluminum.

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Small dot to test the accuracy.

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Looks good. Plunge the pilot drill through the material. Then without moving the part, table or vise. Change to the 0.121 inch drill bit, use a drop of oil, and drill through.

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Without disturbing the part. Change to the 90 degree countersink and start the process. I test fit the screw to make sure it sits just below the surface.

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The XY compound table lets me move the part without removing it from the vice keeping the part square at all times. Repeat for the other body post hole.

The guide is next. Tools required. Number 27 drill bit. Number 2 pilot drill.

Same exact instructions to drill this hole but no countersink. Pilot drill first (dry). Drop of oil. Then number 27 drill bit after (for Slot It guides). When you have just the right pressure on the drill bit. The material comes out in two large twisted strings.

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More to come...
 

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KRZ

Most informative. Thanks. Been thinking for a while that a length-adjustable version of your chassis could be marketable.

Alternatively, non-adjustable units built to order. I'm thinking aloud, of course.
 

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Now that the guide and body posts holes are done. We need to flip the part 90 degrees in the vice and locate the cross-hairs for the bearings with the pilot drill.

Tools required. Number 2 pilot drill. Number 14 drill, and a 3/16 inch reamer.

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Pilot drill completed. That sets up the accuracy to drill straight through both sides of the aluminum tubing. The larger number 14 drill brings the hole to within .005 thousands of an inch to the required size. A reamer can't drill a hole. Only finish it off... very accurately. Remember not to move the part while going through the steps. Don't forget a drop of oil before every machining process except for the pilot drill.

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You can see a bit of aluminum hair left on the reamer. That's all the material it needed to remove to make it a perfect bearing fit.

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The compound table is now move over and adjusted to do the other bearing saddle. Same steps again. Pilot drill. Drop of oil. Number 14 drill. Another drop of oil. Then the reamer. Now you end up with a square piece of tubing with lots of precision holes.

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The bearing saddles are marked with a special jig (aka popsicle stick). Then a line is drawn across the bottom to help avoid damaging the material while cutting.

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Then the bandsaw fun begins. Everything free-hand.

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Now we have a roughed out chassis.

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More to come...
 

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Discussion Starter · #4 ·
The guide hole needs a line scribed about 1.65mm from the edge to help prevent going too far with the file.

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The rear body post needs a line marked so it also doesn't get filed too far.

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Bandsaw rough cut.

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The bandsaw was very carefully used to remove rough material around the guide.

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A disk sander finished off the rear of the chassis to a super smooth finish.

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A hand file finished off the guide area. It's ready for assembly.

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Thank you very kindly for looking.

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Here's about half of the scrap from the other chassis's I've previously built.
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I used to throw it away when I first started down this path.

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Kindly let me know if anyone has questions?

Ken
 

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Discussion Starter · #5 ·
A small slot may need to be added for the crown gear. I'll only know after test-assembly.

My apologies for any mistakes or typos. It's almost 4AM here.
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Completing the chassis and car is next.

Thank you very kindly.
 

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Thanks for this, Ken. This is metalworking at a very high level of skill. Although you describe it modestly, I know from my own efforts how easy it is to end up with out-of-line holes which I then 'bodge' into line by making them oval! I'm always reluctant to invest in the right tools, too - I guess there's a lesson there.......

Mike
 

· Jim Moyes
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Really interesting KRZ! Thanks for sharing.

Just a thought - would starting with 3/4" x 1-1/2" box not save a lot of the waste in your last pic? If such a thing is available.

Or do you have a good source of the 3/4" that you use?
 

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Discussion Starter · #9 ·
Thank you very kindly Kevan, Mike, and Mr.M.

A man can't have too many good, quality slot car tools in his shop. It's against "slot car" laws... somewhere.. I'm sure.
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Mr.M. This material is very cheap from Home Depot. It takes about $3 of aluminum to make one car. Being square makes the material a bit stronger in the vise. I plan to take all the cut-offs to a scrap metal buyer soon to buy... a coffee maybe?
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Discussion Starter · #15 ·
These out-corner many RTR cars because the CG is really low. The entire chassis weighs 7-grams. The upright bearing supports weigh almost zero. Installing 10-grams of lead to the bottom makes the bulk of weight 1mm off the track.
 

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Discussion Starter · #18 ·
I forgot to add.

For NSR or Slot It univeral guides with screw = #27 drill bit.

For Mr Slotcar univeral guide with screw = #25 drill bit.

Hi Matthew77. I documented and built this chassis last night in real time. I will be happy to show everyone the car when it's completed. There's a big mess to clean up in the shop at the moment. Who did that??
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All my builds so far have been on file. The tutorial required a fresh build for the sake of pausing for photos during each step.

I hope to race this car this coming Tuesday night in slow Sports Car class. It won't take long to finish.
 

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Discussion Starter · #19 ·
A little bit of progress.

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More to follow. Thank you very kindly for looking.
 

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