[Matt Reiland]

Originally Posted by Andy Baker

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.

What Andy says above goes without saying, we have duplicated much of the designs from the dog style shifting transmissions and I can't buy and have fabricated the individual pieces for 2 transmissions for less then $800 which makes the $330 ea. seem like a steal. I have contacted Andy more than once to question how he is selling pieces that are already machined to the proper size and tolerance for cheaper than I can get the STOCK!!!! We went with the single speed this year for simplicity but I think the evolution of Andy's gearboxes will be more options into the same base designs such as encoders, and possibly something like a servo shift. We servo shifted the dog transmissions with no issues over the past 3 years and it works well if you're not using pneumatics on your robot. We also changed to design for our use with a high engagement arc to make sure they slammed into gear at full speed. This makes the whole drive train slightly 'sloppy' (maybe an 1/20 of a rotation at the drive wheels without any rotation of the motors) but the encoders are downstream of the dog and compensate for that.

My thoughts anyways.......