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    1. Kit: , by (VIP/Sponsor) gbritnell is offline
      Builder Last Online: May 2019 Show Printable Version Email this Page
      Model Scale: 1/8 Rating:  Thanks: 0
      Started: 05-03-13 Build Revisions: Never  
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      Gentlemen,
      In xken's thread about the Allerton steam pumper there was some conversation about my rearend looking good at the NAMES show. While this may have been taken out of context (never) I thought that maybe I could enlighten everyone.

      Many years ago when I built the 302 V-8 engine I would get asked from time to time "when are you going to build the rest of the car?" To this I would respond "probably won't happen."
      Now a couple of years ago I built a 1/3 size Borg-Warner T-5 transmission and when I would put it out for display I would get asked "when are you going to build the rest of the car?" To this I would respond "probably won't happen."
      Well this winter's project was to build a 1/3 scale 9 inch Ford differential. I had all 3 pieces on display at the NAMES show the end of April and upon seeing them people asked the same question. This time I said, "I'm working on it." Somewhere in the future I hope to have the full chassis complete and eventually turn it into a 32 Ford street rod.

      The project got started when I was at a buddies house for our weekly car get-together. Over in the corner I spotted this 9 inch center section sitting in a plastic bucket. The winter idea was sparked and I took the 'heavy' bucket home. Over the next couple of weeks I cleaned it up, pulled it apart and measured and made sketches of all the parts. Upon completion I sat down with my Cad program and started making formal drawings.

      With the full sized diff having hypoid gearing and while having seen this type of gearing many times I really didn't know what was involved in recreating it so it was off to Youtube and Google. What I came to find out was that hypoid gearing is a gear generating process that involves way more than the home shop machinist can create so an alternative gearing setup was investigated. I found in some old magazines a construction article with the attendant math to create what is known as skew bevel gearing. With a lot of math help I was able to make the required cutters and cut a test set from Delrin. With the gearing proven I went ahead and cut the gears from steel (ring gear) and brass (pinion).
      Had I not been able to cut gears the project wouldn't have gone any farther.
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  1. gbritnell's Avatar VIP/Sponsor
    Name
    George
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    Jul 2006
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    For those of you that have followed my build threads on the radial engine and the T-5 transmission you are familiar with my machining and construction techniques. Most all of my work these days is scratch building from bar stock. This project is the same so I won't include all the construction pictures. (many) The block of aluminum was machined to it's overall dimensions, laid out to give rough guidlines for machining, and then the whittling began. The first steps are to machine shaft and bolt holes and then carve out the inside. If the outside is cut first then there's generally nothing to clamp to for finishing the inside shapes. 80% of the contour radiusing Ford 9 inch differential (in 1/3 scale) was done by the step-off method, over so far then down, over so far then down. The remaining 20% was done on a rotary table. The following pictures show the diff housing from many angles.
    gbritnell


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #2

  2. gbritnell's Avatar VIP/Sponsor
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    George
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    The next piece was the pinion housing. Although not as complex as the main housing simply by virtue of it being smaller there was still a number of machining steps to complete it. I started in the lathe with a piece of round stock and cut the main diamters and bored for the bearings. Once the lathe work was finished it was on to the mill with work done both in the vise and dividing head. The flange shape was formed as were the pockets and bosses. With the machining completed the part was hand worked with a Dremel Ford 9 inch differential (in 1/3 scale) flex shaft grinder using burrs, stones and polishing sticks. The radii and tight corners were finishe with small riffler files of various shapes. The two finished parts were then assmbled to see how they looked.
    gbritnell


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #3

  3. jfonticobal's Avatar VIP/Sponsor
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    Javier
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    Ooooooooo my God. Awesome
    QUOTE QUOTE #4

  4. xken's Avatar VIP/Sponsor
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    Kenneth
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    George, great work as ever! Still looks as good as ever. Keep up the great work.

    Ken
    QUOTE QUOTE #5

  5. gbritnell's Avatar VIP/Sponsor
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    George
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    When the initial machining was done, bored and drilled holes, the trunnion holes for the spool bearings was done except for the threading. Once the housing was finished it was time to thread the trunnion holes for the adjuster bushings. A steel bar was turned up to just .0015 larger than the holes, the caps were loosened and the housing was slipped onto the bar. With the housing in place leaving about .35 depth for threading the trunnion caps were tightened to hold the housing tight to the bar. Trying to keep everything as close to scale as possible I found a 23 mm bearing that would work so the threads were .906 at the root of the thread and had 48 tpi. The caps were done after the housing as it's always easier to make the external threads fit the internals.


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #6

  6. gbritnell's Avatar VIP/Sponsor
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    George
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    The spool was made from cast iron. I purchased the 2 large bevel gears and 1 steel pinion gear. I then used the pinion gear to make my own cutter to cut 2 new pinions from brass. The reasoning behind this is that running the same kind of metal against itself causes rapid wear so my reasoning was to have the gears made from steel and brass to prevent this. Had I thought just a little farther I would have realized that the spiders only work going around corners so the material would have been irrelavent.
    Anyway the gears were made and fitted into the spool making shims to adjust for tooth engagement.
    gbritnell


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #7

  7. gbritnell's Avatar VIP/Sponsor
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    George
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    At this point I'll backtrack a little. If you look at the picture of the brass spider gear you'll notice steel splines inside. I have in the past made my own cutters to broach splines but found in the process that to cut any kind of depth to the splines up to 6 cutters needed to be made, each one progressively larger than the next. Along with that it takes a tremendous amount of press to broach them out. While making the drawings things like the splines, bearing sizes, nuts and bolts etc. need to be sorted out ahead of time so I found commercially made spline stock that was close to the scale I needed. This worked for the axle splines but the U-joint yoke would be another story. There was nothing available and even if there was it would mean coming up with some way of fabricating the yoke so this meant making up another set of tooling to try and cut my own splines in the yoke. I made the broaches from W-1 drill rod (water hardening). I didn't have to cut too deeply so I made 3 broaches with progressively deeper teeth. Each one had a pilot .001 smaller than the root diameter of the hole and the second and third broaches had the pilot along with a set of teeth that matched the previous teeth so they would align before the cutting would start.
    The broach teeth were cut with another shop made cutter that served both as the broach cutter and the pinion shaft cutter.


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #8

  8. gbritnell's Avatar VIP/Sponsor
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    George
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    Before I spent a lot of time machining the yoke and not knowing if the spline cutters would work I bored out a test piece of steel. With some cutting oil and my arbor press I was surprised that the cuts went easier than I had imagined. At this point the U-joint yoke was machined and the splines were cut into it. I was still a little apprehensive that there might be a problem but the yoke came out well.


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #9

  9. gbritnell's Avatar VIP/Sponsor
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    George
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    The pinion shaft was machined and splined and the pinion gear was pressed on and pinned in place. A spacer bushing was made to the calculated drawing dimension and slipped on place first. Any further adjustments to the pinion depth would be made by shims between the pinon housing and the main case, as per full sized units. At this point a lot of small parts needed to be finished, bolts, seal bushings, adjuster locks etc. The center section (pumpkin) was then assembled and adjusted.
    gbritnell


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #10

  10. gbritnell's Avatar VIP/Sponsor
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    George
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    The ring gear was bolted to the spool. The spool bearings and bushings were installed. The ring gear assembly was bolted in place and the gear mesh was set with the slotted adjuster rings on either end. Once in place the keepers were bolted on to prevent the rings from turning.
    gbritnell


    Ford 9 inch differential (in 1/3 scale)
    QUOTE QUOTE #11

  11. fuzzy's Avatar Established Member
    Name
    Ted aka Fuzzy
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    Nov 2005
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    Jewelery in 1/3 scale ! As always,George you amaze us. Thanks for the in process pics.
    QUOTE QUOTE #12

  12. Roger Zimmermann's Avatar Yearly Subscriber
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    Roger
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    I'm really impressed. Could not do that with the simple machinery I have.
    QUOTE QUOTE #13

  13. ScaleMaster's Avatar VIP/Sponsor
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    Mark
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    That is gorgeous!
    Build what you want and build it for yourself, the rest will follow... - Mark D. Jones
    QUOTE QUOTE #14

  14. Bandit's Avatar Member
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    Alexandre
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    Nov 2013
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    Totally AWESOME!! I'm litterally SPEECHLESS!!! Could you do the same with a GM 8''1/2 complete housing in 1/8 scale for the Monogram Trans Am by any chance?? LOL!! By the way, your nickname really reminds me something, GBritnell...Have you ever been on the Scale Auto Magazine forum????
    QUOTE QUOTE #15

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