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love of Ampeg and other Scroll Basses, Part 2

Discussion in 'Basses [BG]' started by smperry, Jan 9, 2014.


  1. Bobo

    Bobo

    Apr 11, 2017
    CT
    ps, i always liked seeing a spider on the road! haven’t seen one in a long time!
     
  2. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I started my career as a sports car mechanic, working in a small shop in Pennsylvania. I worked on a lot of Alfas, Volvos, Triumphs, etc. I even did a partial restoration on a 1967 Ferrari 330 GTC. Getting to disassemble a Ferrari in detail was a big chapter in my engineering education. This was when I was 19, before I started college for engineering. Then I got a job in the world of auto racing. I paid my way through college doing R & D on race cars, and building an advanced (for that time) engine dyno facility. I think I honestly learned more about machine design from those days than I did at Penn State.

    One big lesson I learned from race cars that I apply today to my instrument design: A race car that wins races is only 1% better than its competitors. That 1% is rarely from one single secret trick. It's the summation of hundreds of little tiny tricks. Each little trick is only worth 0.01%, and you might think that's not worth the trouble. But do a hundred of those little details and you get 1%, which wins races. On the negative side, a single small thing overlooked can cost you 1% or 10%, or it blows up!

    Race cars are one of the purest forms of engineering. Engineering is about perfection. Looking at every single detail, making every one as best as it can be, and not missing one. One missed detail can ruin all the good details. Above all, don't miss anything. Every detail must be considered.

    Improving the sound of an electric bass requires a whole bunch of little detail improvements. People look at one of the improvements and scoff that it won't make any difference that you can hear. But, put them all together and you've got something. Miss one, and they won't work.
     
    diegom, dloase, Runnerman and 6 others like this.
  3. Bobo

    Bobo

    Apr 11, 2017
    CT
    I’ve got my money on you and the 1%, Bruce! It’s always made me smile over the years when someone comes up to me stba gig and asks, “Is that a custom bass?” and I tell them that it’s an Ampeg. I look forward to the next gen of inquisitors who will look at #016 and ask, “Is that a custom bass?” and I’ll say “Why, yes, yes it is!” Thanks for the back story, Bruce. And thanks for compiling all the little details. Cheers, Bobo
     
  4. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    #016 isn't really a custom bass. It's a standard production Walnut AMB-2 with no custom features. The production rate is definitely low (and slow :rolleyes:), and I'm still sorting out a few design details as I go.....but I don't do custom basses any more. I got out of that business.
     
    Bobo likes this.
  5. Bobo

    Bobo

    Apr 11, 2017
    CT
    That may be, Bruce; however, this is the first time someone has built me a bass. It may be a standard build, but it is now, and will always be, a special build to me. I understand what your saying, and I appreciate your position. Even your standard build basses have something all the other builders do not; they don’t have your 1%!
     
    Joshua likes this.
  6. farace

    farace

    Jul 9, 2016
    Connecticut USA
    It's possible now to register "Year of Manufacture" plates and put them in a car if you can find them. My dad was going to do that with his '54 Plymouth, but never found any. And by '71 Connecticut had long gone to the registration stickers, so it's not an option for me (would love to have an Italian plate, but that's not allowed).
     
    Bobo likes this.
  7. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    More steady progress toward finishing #016. And all the other AMB-2's in line.

    Here I'm making up the tooling to make up the new Hot Split pickups. The Hot Split pickup has a different size outer housing than the previous standard (baseline?) AMB-2 pickup. The housing needs to be 1/8" taller in height to fit the taller bobbins, which have more windings. And, I'm also dividing the pickup into two halves, one for each bobbin.

    I make up the outer housings of the pickups by casting them in a silicone rubber mold. The perforated brass shielding shell and the completed coil are set down into the mold, and it's poured full of black West Systems epoxy. To make the silicone rubber mold, I first have to make up a Master. This is an exact-size form of the outer size/shape of the pickup, which the silicone rubber is poured over. I like to machine the Master from aluminum, carving it from an aluminum block.

    It's time to use my big machines, which is just plain fun! I start with a chunk of 2" square 6061 bar stock, clamping it in the vise of my big Kondia Milling machine. And the chips start flying! I mill away the front and back surfaces of the block, leaving a raised center section.

    As I've said before, having a big milling machine is a necessary part of life. It makes things.

    IMG_6852B.

    IMG_6853B.

    Milling small steps to rough out the 7 1/4" radius top surface.

    IMG_6854B.

    Over to my big horizontal bandsaw, to saw off the section that I need.

    IMG_6855B.

    And there's the rough-machined blank. In the background is the Master for the standard one-piece pickup. You can see how it's shaped and smoothed and polished. That's coming up for the new one.

    IMG_6856B.

    To the left is the prototype Hot pickup, in the one-piece housing. I still haven't tested it yet. I'm just going ahead with the tooling, on the assumption that the extra windings and height will work well. As soon as I finish the tooling, Ill build up a Hot Split set to go in #016. Since #016 is in the final stages, I may as well just finish it and use it to evaluate the Hot pickup, comparing it side-by-side with my AMB-2 #001.
     
    diegom, Ed Bloom and Bobo like this.
  8. Bobo

    Bobo

    Apr 11, 2017
    CT
     
  9. Bobo

    Bobo

    Apr 11, 2017
    CT
    I concur! Thanks for the update, Bruce, and for explaining the process. This is awesome!
     
  10. Bobo

    Bobo

    Apr 11, 2017
    CT
    702C2376-D955-45E6-9479-6F2117CB310D. 8DF7C191-AE51-4F45-87D1-F1D70AF42D66. I got to perform with my friends Robert Silverman, Doc Halliday and Scott Hamilton at Ashford and Simpson’s Sugar Bar on West 72nd Street in New York last night. Tom Macdonald, who I performed with at Carnegie Hall on November 6, 1976, sat in with us for a rousing version of “Shake, Rattle and Roll.” A wonderful time was had by all.
     
  11. Bobo

    Bobo

    Apr 11, 2017
    CT
    DC9D9FBE-6FF0-4532-A287-D1DBA5F23B78. back in the day, c.1985
     
  12. Bobo

    Bobo

    Apr 11, 2017
    CT
    please note: i had hair, it was dark, i was wearing a watch, i had a 30” waist. memories...
     
    jumbodbassman and Ed Bloom like this.
  13. dloase

    dloase

    Jun 20, 2016
    As always Bruce, love to see your process, and to hear you stories. Your 1% is well worth the waiting we do on this end.
     
    Bobo likes this.
  14. Bobo

    Bobo

    Apr 11, 2017
    CT
    ditto!
     
  15. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I finished up the Master for the Hot Split AMB-2 pickup today:

    The next step is to drill the holes for the location dowel pins. These pins are used to accurately locate the aluminum base plate on the bottom of the pickup, during the casting process. I drill holes in the base around the master, accurately positioning them from the Qcad drawing data. I do this in my trusty green Mill/Drill machine with the digital readouts.

    IMG_6858B.

    Next, I clamp it in the vise and file the lump of the Master to shape. By hand, with files. Just as if it were a block of wood. No stinkin' CNC's or 3-D printers here! I used a couple of big 14" files to rough in the half-radius on the top, then smaller files to smooth out the sides and gently radius the edges all around. I finish up with a #2 Swiss file. Then smooth it off to a satin finish with a Combi-Flap wheel in an electric drill.

    IMG_6860B.

    And here's the finished Master. I didn't polish it up to a high shine; not necessary because the outside of the cast pickup gets all sanded anyway.

    IMG_6862B.

    I plugged 1/8" x 1 1/4" steel dowel pins in the holes. When I cast the silicone mold, it will leave these deep 1/8" holes in the mold, in accurate relation to the shape of the pickup. Then I'll plug similar dowel pins into the mold itself, leaving them sticking up above the surface. When I cast the pickup, I'll place the aluminum base plate down over those pins, which will hold it in alignment with the pickup. There are four pins, but the split base plate half has only three screw holes. I put in the four pins so that I can use the same mold to cast both the right and left pickup halves, flipping over the base plates. You'll see in the coming steps.

    IMG_6861B.
     
    aetheriac, Bobo and Ed Bloom like this.
  16. Bobo

    Bobo

    Apr 11, 2017
    CT
    Bruce, thanks for documenting and sharing this whole process. I’m sure everyone else finds this as interesting as I do. My brother is a woodworker and is blown away by your whole process. “No stinkin' CNC's or 3-D printers here!” You, you’re good, you! Cheers, Bobo
     
    Ed Bloom likes this.
  17. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Continuing on with making the mold for the Hot Split pickups;

    With the aluminum Master done, it's ready to be used to make the mold. I saw a 2" wide strip of 3/4" MDF, then cut it into four blocks that are fitted tightly around the base of the Master.

    IMG_6863B.

    I coat the surfaces and ends of the blocks with Johnson's Paste Wax.

    IMG_6864B.

    I assemble the blocks around the master on a strip of waxed paper, and hold it all together with clamps.

    IMG_6865B.

    Mix up the silicone rubber mold compound, and pour it in around the master, up to the top edge of the blocks. It'll take about 12 hours to cure. This basic technique is how I make all of my molds. It works very well. I can pour as many molds as I want, to speed up production. I clean and store the Master and the blocks, ready to make up a new mold whenever I need it.

    IMG_6866B.
     
    GKon, Bobo, farace and 1 other person like this.
  18. Bobo

    Bobo

    Apr 11, 2017
    CT
    “Johnson's Paste Wax”...coincidence?...
     
    farace likes this.
  19. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    There's actually no connection; it's just a really good product that I use a lot. But I like to pretend there's a family tie. It's from the SC Johnson company; my dad was SC Johnson.
     
    Ed Bloom, GKon, diegom and 1 other person like this.
  20. Bobo

    Bobo

    Apr 11, 2017
    CT
    I was pushing your leg! I do have a can on my shelf. Always have, always will.
     

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