The Thrifty Bot: 8mm Keyed Motor Output Shaft Pre-Order


Note: This is a pre-order of a pack of 8mm keyed motor output shafts. Production will begin mid-November with the expectation of shipping by end of November.

Use the same gear pinions that you’ve always loved with the 8mm Keyed Motor Output Shaft. This output shaft will allow teams to utilize keyed motor pinions historically used on legacy FRC motors.

  • Material - Evaluating stainless steel samples
  • 2mm wide keyway, 20mm long
  • 34.8mm (1.370") shaft length from front face of motor
  • Estimated weight of .05 lbs per shaft
  • Sold in 5 packs ($12 per shaft) or 20 packs ($10 per shaft)
  • Free Shipping on pre-orders of this product
  • Application drawing and 3D STEP CAD available on product page

Now that I think about it, are there future options for 1/2" hex and other common shaft sizes such as 3/8" hex? Maybe a shaft with an integrated VP Female Adapter.


Thanks FRC Costco!


FRC Costco, where all your dreams come true

Ryan’s got a deal for you

Edit: For the uninitiated


Then who’s FRC Sam’s Club?


Somehow I’m not surprised that the Thrifty Bot was the first to come out with this.
I wonder why…


Unless it’s multiple pieces I don’t think this would be possible. You have to access the screws to attach the shaft to the motor and the front mounting plate/bearing has to slide over the shaft. At that point it would be way easier to make a falcon spline ID hex OD adapter.

Do we know that this will be considered a legal modification of the motor?


If Vex is selling replacement shafts I don’t see why it wouldn’t be. Great product.


Thank goodness… This is what pro-consumer looks like!


Hey Ryan!

I was kinda confused on the purpose for this product because each shaft comes out to $12 per shaft not including shipping (after preorders are done). Isn’t the purpose of the falcon spline shaft to make it a no hassle installment of the motor pinion? It also didn’t make sense to me because the most expensive thing for the falcon would be the 16t GT2 pulley at only $1 more than it is per shaft and saving $2 per new motor pinion. I think that this would be a cool product if vex didn’t make it super easy to transition to the new motor shaft style. I personally haven’t reused a motor pinion before just simply because they are so cheap and tend to wear after a whole season. I understand that maybe this is for those that have the old style pinions still and don’t wanna buy new ones but still the cost I mentioned above to run old technology is kinda a moot point.

Can you please let me know what your intent was with this product and exactly how it fits into the market because I currently don’t see how it would fit? Maybe I am not a true visionary like yourself. :smile:

Thanks in advance!

The quick and easy answer is that not every pinion gear or pulley that a team may want to use is available with a Falcon spline. The ones that Vex offers are, but 8mm keyed shaft is a standard shaft, so if a team wants to use a pulley from SDP-SI or another industry vendor, the 8mm shaft version lets them do that, not to mention what’s available from other common FRC vendors.


I’m buying this because I don’t want to buy a new pinion library for R&D.

Once I know what we’re running this year, I’ll get splines for the competition robot.

Over time, we’ll transition onto more and more spline pinions. Especially if we can get splined pulleys to print OK.


It’s pretty simple really - I saw a lot of people asking for an 8mm keyed output shaft option. Teams have decades worth of stuff that works with an 8mm keyed output shaft.

I’m not knocking the spline output shafts either - they’re very cool and will be great long term. I’m just trying to provide teams an option that many requested.


Hey Ryan,

Thanks for the quick response! Based what others prior to your response have said it basically shows what you are saying. Makes more sense why you launched/created the product. What can I say… gotta give the people what they want. :wink:

Sorry I didn’t see how simple it was prior to posting :cry:


Been thinking about this since you posted last night… Would you care to share any stress analysis you’ve done on the part? Since no one has motors in hand yet, and I doubt you even have pre-production samples of this shaft yet (that would be incredibly fast turnaround!), it leaves a small question in the back of my mind of the risk of shaft failure under competition conditions. Having real-world testing is, of course, best… but I know that can largely be simulated these days to give you a good idea of how it would fair - both under full stall and shock loads we can expect to see in various applications on a robot.

Of course, implicit with this is the assumption that the shaft that comes with the motor has been fully tested by Vex, with a generous margin of safety before failure in normal usage conditions. But they have actual, physical parts to play with and test out, not just a CAD rendering.

Jon -

These are all really valid questions and points. I should have samples in hand early next week and definitely plan to do some real world quality testing. The last thing I want to do is sell teams something that will fail in the field and if testing shows the parts don’t meet our high quality standards, obviously everyone will be refunded their pre-order funds.

I’m actually getting samples in a few different materials to test as well, I will update the OG post to reflect that.


What materials are you trying? Are you trying to match the same material as Vex’s falcon shaft or is that unrealistic/impossible for you to do? Or is their material not even the best

Great to hear! I assumed you guys had analysis and testing plans in place, but it’s nice to get that out in the open for anyone interested in it :slight_smile:

Suggestion for another product: A Falcon spline shaft to hex adapter. Similar to the 8mm to hex adapter AndyMark has:

I know we’ve used that one in the past!

This is much harder/impossible without having a broach or something that can cut the spline pattern, and there’s nothing definitive everywhere that even documents what the spline is.

I would think that a hex adapter would be something that VEX and/or AM is already planning on selling, would be surprised if they do not.