C-Can Motor Building Steps
Some notes about motor building: what follows, in outline form, are the steps I follow when building any given C-Can motor. And no, I didnt think the list would be this long, either. After actually documenting what I did, I was surprised by the number of steps, checks, measurements, and general fiddling around I went through in what I had always presumed was a simple, straightforward process.Not to worry. As it turns out, theres a big difference between "complex," which is what this appears to be, and "difficult." None of these steps, taken by itself, is beyond the ability of an average slot car drag racer; there are simply a lot of them. Some may require tools you presently dont own, some may involve procedures you may not be familiar with, and the point of some may escape you.
To paraphrase a note I include in my "Tools" presentation: what you end up doing is usually determined by the manner in which you end up approaching motor building. I figure it this way: if you have some idea about how you might do it, and a few suggestions about how you possibly should do it, you can make a more informed decision about how you will do it.
One final word about motor building: the best way you can learn about motor building is - surprise! - to build motors. Experience is a great teacher, not to mention occasionally providing those magic, humbling moments that can be described either as "Oops!" or "Oh, ****!," depending on their cost. Dont be afraid of messing something up or building a motor that doesnt perform up to your expectations. Everyone does it. Regularly. Anyone who claims they dont is either lying to you or suffering from some pretty low expectations. We all build dogs now and then, and you will, too. But when you establish a solid building method, youll have a better idea of what - and what not to - blame and/or change.So good luck, and lets get on with it, shall we?
Unca Frank
(What you see below is probably going to have to do for the time being; I estimate approximately 9,000 to 10,000 additional words are necessary to describe them, covering each meaningful step, even without illustrations. At these prices, figure on waiting a while for additional content. In the meantime, if you're curious about what some step may mean or entail, e-mail me.)
Motor Building Steps (by component area)
Can Work1 Selection and Measurement2 Bushing removal
3 Can Sizing
4 Interior prep
5 Exterior prep - "ear" evening
6 Bottom flattening
Endbell Mounting7 Bushing Hole centering
8 Seam soldering
9 Endbell screw hole cleanup10 Bushing/bearing soldering
11 Mounting screw tapping (or)
12 Can mount tinning
13 Alignment tool insertion14 Endbell-to-can alignment
15 Screw hole drilling
16 Screw tapping & insertion by sequence - oiling17 Disassembly
18 Endbell hole deburring
19 Reassembly & bushing alignment check
Magnet Installation
20 Selection, inspection, Gauss reading, matching
21 Insertion & measurement - thickness, centering, & configuration
22 Polarity/orientation check
23 Magnet Cleaning
24 Adhesive selection & prep
25 Final magnet installation
26 Positioning & measurement
27 Excess adhesive cleaning
28 Baking (if necessary
Magnet Honing
29 Hone & diameter selection
30 Hone installation
31 Clearance checking
32 Can-endbell assembly
33 First (or sequential) honing - heat
34 Disassembly & cleaning
35 Bushing/bearing cleaning & checking
36 Final dimension honing
37 Polishing
38 Disassembly & final cleaning - i.d. engraving
Armature Prep
43 Timing check39 Selection - Design, winding, balance, timing, commutator, length
40 Arm diameter measurement
41 Arm stack length measurement
42 Com diameter measurement
44 Arm meter reading
Armature SpacingEndbell Hardware Installation45 Initial arm installation & can assembly - com & arm shaft spacer shortening, if necessary
46 Endplay inspection & measurement
47 Disassembly & preliminary spacer addition
48 Reassembly
49 2nd spacer measurement
50 Reassembly
51 Additional spacer measurement(s), as necessary
52 Disassembly & cleaning
53 Endbell inspection, internal/external deflashing, internal "radiusing," as necessary
54 Hardware checking & inspection - trimming & deburring - brush backplate flattening
55 Hardware cleaning & polishing
56 "Slug" or shaft installation
57 Brush backplate installation
58 Brush hood alignment tool installation
59 Endbell-to-can assembly
60 Brush hood and spring post assembly
61 Hood alignment & tightening
62 Alignment checking - com degrees vs. alignment tool degrees - advance/retard
63 Brush hood & back plate clearancing & honing
64 Hardware tinning/soldering
65 Internal screw facing - endbell cleaningBrush & Spring Prep
Preliminary Assembly of Motor66 Spring selection & matching - brush arm length matching & deburring
67 Brush selection
68 Brush honing - radius vs. break-in time
69 Brush shunt/spring slot prep- insulated vs. non- insulated
70 Brush deburring, cleaning, & polishing - brush orientation identification/engraving
Initial Motor Break-in71 Can & endbell final cleaning
72 Arm & spacer installation
73 Endbell attachment - final checking - installation of brushes and springs
Armature Shaft shortening74 Initial oiling
75 Standard (nominal) break-in procedures
76 - 5 minutes @ 3 volts, temp check, cool
77 - 5 minutes @ 4 volts
78 - Disassemble, inspect brush face & commutator condition
79 - Clean, reassemble, reoil
80 - 5 minutes @ 5 volts, high-voltage checking
81 - Disassemble, inspect, clean can, endbell, spacers, brushes & springs
Shunt Wire Installation82 Arm shaft measurement & marking
83 Shaft cutting & deburring
84 Motor reassembly & reoiling
85 Shunt wire selection & construction
86 Shunt wire prep
87 Shunt forming, shunt & spring oiling, can screw removal, soldering, trimming
Gear Installation, Final Cleaning & Break-in
88 Shaft oiling & removable "barrier washer" installation, end cleaning
89 Shaft tinning
90 Gear prep & installation - tooth inspection
91 Brush & spring removal, final cleaning
92 Brush & spring reassembly, reoiling
93 Final break-in: 10 minutes @ 5 volts
94 Alternate break-in procedures
95 Motor data recording - amps vs. volts
96 Rezap magnets/motor
Motor Care, Storage, & Installation Tips
Avoid motor-to-motor contact. Whenever possible, use nonmetallic storage containers for motors.
Avoid shock and excessive heat, particularly when soldering a motor in.
Insure some free play (adequate gear lash) throughout the total rotation of both gears. Rotate the spur
gear 5 or 6 times to check all mesh relationships. When in doubt, use the "plastic bag shim" method.
Clean the motor periodically. Pure naptha is less aggressive than motor sprays, less hostile than starting
fluid (ether), and reasonably inexpensive. Make certain the motor has been dried and oiled before putting
it back into service.
Periodically check bushing motors for wear between rebuilds. The can end bushing is subjected to the
most side loads, and generally is the first to show signs of wear.
Disassemble, inspect, rebuild, and rezap your motor before it becomes necessary, either after X number
of passes or X number of Races. It will perform better over a longer period of time if you perform
"periodic maintenance" rather than "emergency repairs."
Maintenance/Rebuilding GuidelinesDisassembly & cleaning - parts segregation - shaft bearing/bushing surface inspection
Spring inspection, checking, & reuse
Brush replacement or reuse - temp hardening
Commutator turning & surface finish - minimum material removal - recording number of
rebuilds/com diameter - minimum safe diameter
Rezapping after every rebuild
Replacing bushings/bearings - accurate motor "slugs" - avoiding heat
Rebalancing - when and what kind of arm
The Bottom Line
After all this, you may still be asking yourself "Why bother? I can just buy a motor off the wall and be done with it." Well, sure you can, but not just any motor.
Figure it this way: the parts alone for a good Grp 12 motor retail for between $55 and $60. At, say, $6.50/hr labor rate (not excessive by any means), and 5 to 7 hours worth of labor in a motor, you end up with a total cost of between $87.50 and $105.50. How many of those parts and how much of that precision labor do you suppose are included on the $28 motor youre eyeing on the wall at your local shop? Uh huh.
To make it a little clearer, let me give you my estimates of just some of the improvements that make a "prepared" motor better than a non-prepared one:
Properly honed, matched, zapped magnets: +7-10%
Low-inductance, well-timed, balanced arm: +3-5%
Low-drag, well-sized brushes, matched springs: +1-2%
Low-drag, accurate bushings, can alignment: +½-1%
Can airflow characteristics, arm/shaft lightening: +½-1%
Net result? a 12% to 19% improvement in the theoretical performance of the motor, or, to put it another way, approximately the difference between a Grp 12 and a Grp 20 motor. Is that clear enough? It goes a long way towards explaining why some 90-gram Grp 12 cars run the quarter mile in the .840/.850 range, while others run it in the .890/.900 range, doesnt it?Build or buy, you now have some information to base that decision on. In the long run, its still your money and your choice, so make the best of it!