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Sunday, December 11, 2016

New Brakes for Shine



Jeff “Brakes are for Sissies” Hughes would never approve of what I’m doing to the 1961 Fox Go-Boy Kart (AKA “Shine”).


Shine is almost completely stock, and with the twin West Bend 580 engines, it looks very similar to the Fox advertisement for the 1961 Karts. 


While restoring Shine I had an issue with the brakes.  You can see that the original hub is distorted at the axle hole.  Also, the 5” Bendix brakes offered no cooling. 




So I checked the Vintage Karting rules to find that an upgrade in the brakes is allowable.  Shine is  “… an original production Kart from the Historic Era (1964 and before) …”  however, “…Modern brake upgrades are permitted and recommended.”  So I decided to upgrade to 6” drum brakes. 


There was a problem with this idea: the larger drum could not be mounted in the stock frame location since it would conflict with the left rear motor mount, and possibly the recoil starter on the left engine.  So I turned to my Coaster Train buddy, Dr. Tom Bartol for a solution.  Tom is a scientist at the prestigious Salk Institute, but he is also a first-rate machinist.  Tom has restored some vintage machine tools including a 1954 Sheldon EM56-B Lathe and a 1962 Bridgeport Series 1 J Head Mill, and he is using them to build a personally-designed, meticulously-constructed telescope.  As soon as I showed Tom the need for a frame-to-brake spacer he began to design the perfect part.


On a Sunday afternoon I took Shine and the new 6” brakes to Tom’s machine shop.  He began by cutting a billet of 6061-T6 aluminum, and then he used the mill to be sure that all surfaces were square and exactly sized to within one-thousandth of an inch. 






Next we moved to the lathe where Tom showed me the art of using a four-jaw chuck, a pilot drill, and finally a boring bar to put the axle hole perfectly in the center of the spacer block.  The process starts with boring a pilot hole.   I was surprised to see that the tools remained fixed, and the part moved!  I enjoyed watching the long, continuous ribbons of cut aluminum wind symmetrically off the spacer and into the bed of the lathe.





Next the hole is bored to finished size with the boring bar.




Once the center hole was perfect, Tom set up the mill for the attaching holes and cutting recesses for the brake backing plate springs.  The stock mounting arrangement was for two 5/16” bolts to hold the brake backing plate to the frame, and also to hold the left rear bearing retainer.  Tom and I decided that it would be possible to machine the spacer and the frame to use two additional bolts for added strength and rigidity.  Machining the two stock holes was fairly straight-forward.  What really impressed me was the trigonometry Tom used to calculate the exact location of the additional (top) holes knowing the circumference of the hole pattern of the brake backing plate while realizing that the holes were 60 degrees apart!  He quickly calculated the X and Y coordinates for the two additional holes.  I knew all that high school math was good for something. 




After boring two new holes in the frame, the assembly of the brakes and rear axle went smoothly.   The spacer fit perfectly giving the new brakes a rock-solid mounting, and plenty of clearance.


I think it is so cool that Tom used vintage machine tools to create a custom spacer for a Vintage Kart!  Thanks Tom!

4 comments:

  1. great story, you should ask Tom to let you run the lathe yourself, I think you would have a feeling of accomplishment when you pull a finished piece out of the chuck.

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    1. Hi Arthur, Tom let me "pretend" to do some of the machining. It was very cool, but I'm happy to have an expert doing the fine machining! You will have to meet Tombthe next time you come to San Diego!

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    2. Hi Arthur, I let Cary perform a couple of pilot hole enlarging operations to get the feel of aluminum peeling off in nice continuous ribbons once you hit the sweet-spot in the feed rate.

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  2. Cool stuff Cary! That thing is gorgeous. Are you going to run that kart or is it show only? I had a shifter kart for a couple of years and it was one of the more thrilling drives I've ever experienced.

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