Transmissions

[Andy Baker]

Originally Posted by lukevanoort

However, we've never built a shifter, since we lack the money to buy AM (why do they cost $330 anyway?)

Since you asked, here is a rough estimation of what it would cost to make only 1 or 2 AM Shifters. These are not our costs, since we make large batches of these at a time.

Gear stock (broached holes not included):
12 tooth CIM: $7 each x 2 = $14
40 tooth: $19
28 tooth: $11
35 tooth: $18
48 tooth: $24
15 tooth: $10 (we make this into a shaft, but I would not do that to make 1)

Total gear stock = $96

To fabricate the 12 tooth, 28 tooth, 40 tooth and 15 tooth gears to fit keyed shafts and hex shafts, you would need to have a set of broaches ($100-200) or pay someone about $20 to do this.

To get someone to machine in the "dogs" to the 35 tooth and 48 tooth gear, that will be a good cost. More importantly is the 0.0005" diameter tolerance on the bearing press fit for these gears. Make the hole too small and the bearing is wasted upon insertion. Make the hole too big and the bearing falls out. This is the trickiest machining operation on the entire gearbox. Expect to pay $20 extra for each of these gears. We sell them separately for less than you could buy a blank gear from McMaster-Carr, by the way.

Gear fabrication = $60

Bearings:
3/8" flange bearings, shielded: $5 x 2 = $10
3/8" flange bearings, unshielded: $5 x 2 = $10
1/2" flange bearing, shielded: $9
1/2" bearing, unshielded: $6
3/16" bearing, unshielded: $3

Total bearings = $38

Side Plate fabrication:
Side plates on these gearboxes have +/- 0.001" tolerance on the shaft hole location. This is not trivial. This means they need to be made precisely. Expect to pay $30-35 per plate on the market.

2 plates = $60

Shaft fabrication:
2 hex shaped shafts are needed. One would simply be lathed down on the ends (or you turn the 15 tooth gear into a shaft as we have). The output shaft needs a keyway, a hole, and a lateral slot. Also, the shifter shaft is needed. It has a lathe operation and 2 drilled holes. The spacer shafts holding the gearbox together will cost about $3 each.

Cluster shaft: $8
Output shaft: $25
Shifter shaft: $8
Spacers: $3 x 6 = $18

Cost of shafts = $59

Dog Gear:
This is not an easy part to make either. I estimate that it would take a machine shop $40 to make this part.

Dog Gear = $40

Oh, and there is that little cylinder plate. It will be $14 to have someone make that.

Cylinder plate = $14

Also, you will need fasteners, spacers, key stock, and plating. For these things, throw in about $5.

So... adding up the costs noted in bold letters, that totals $372. This cost is unassembled and not debugged.

From my point of view, teams are getting a very good deal with $330 for a tried and true gearbox.

Do these numbers seem correct?

Andy B.