[FTC]: Custom Axles

[TheThings5926]

Our team is looking at making our own, larger, hardened axles. Our design last year had us going through more than one pair of axles because we had high torque on the small axle. We were looking at making them the size of a Tetrix motor shaft, this would allow us to use the hardware made for the motor sizes axles. So basically, it is a larger, stronger axles that you can use standard Tetrix hardware with. Would anyone be interested in these?

[RRLedford]

Unless you are giving them away, I do not think it is legal for teams to do group orders for custom made parts.

Also, I advise keeping the axle OD matching the bronze flanged sleeve bearings of the Tetrix parts line, since these sleeve bearings are usually what is supporting shafts and axles, and what fits with the Tetrix channel.

For long shaft needs, you can get hardened shaft in .1875" and make that work by grinding flats where needed.

For shorter needs you can also get extra long 10-32 hardened socket
head cap screws and use them as shafts and axles


-Dick Ledford

[Andrew Rudolph]

The motor shaft of tetrix motors is 6mm, which is ~.236" (Taken from this drawing)

You can get 6mm shaft from McMaster and a number of other sources.

Of course this drawing of the hub shows the bore to be 5.95mm or .234"


I wonder if you could take the motor hubs and drill them out to 1/4" That would give you a bunch of options. The little nub that centers it inside the gear/wheel/etc. is 7.97mm or .313" so there would be material left to center the hub and use them as normal. D profile shaft 1/4" diameter at McMaster is ~$9 for a foot long piece.

[RRLedford]

Originally Posted by Andrew Rudolph

The motor shaft of tetrix motors is 6mm, which is ~.236" (Taken from this drawing)

You can get 6mm shaft from McMaster and a number of other sources.

Of course this drawing of the hub shows the bore to be 5.95mm or .234"


I wonder if you could take the motor hubs and drill them out to 1/4" That would give you a bunch of options. The little nub that centers it inside the gear/wheel/etc. is 7.97mm or .313" so there would be material left to center the hub and use them as normal. D profile shaft 1/4" diameter at McMaster is ~$9 for a foot long piece.

Then what are you going to use as bearings and how are you going to provide support for .250" shafts passing through or across the Tetrix structural elements?

Shaft bearings must be supported. The 3/16" bronze flanged sleve bearings that insert directly into the Tetrix components make assembly so simple.
Any new shaft schemes that are not compatible with them are going to add a lot of work.

-Dick Ledford

[Andrew Rudolph]

Originally Posted by RRLedford

Then what are you going to use as bearings and how are you going to provide support for .250" shafts passing through or across the Tetrix structural elements?

Shaft bearings must be supported. The 3/16" bronze flanged sleve bearings that insert directly into the Tetrix components make assembly so simple.
Any new shaft schemes that are not compatible with them are going to add a lot of work.

-Dick Ledford

I agree that you absolutely need to put bearings to support the shafts, I also very much know the pain of using the small Tetrix shafts for higher torque and higher load situations where the shafts bend and bind and the setscrews are such a pain. Overall the tetrix system has some big shortfalls when we push them to make competitive machines. I am just thinking out loud as to ideas with the new rules on other ways teams can look outside the tetrix catalog for solutions.


With that said the bronze bearings are 3/16" ID and 5/16" OD (basically) as per this tetrix drawing.

Quickly looking at the McMaster catalog I found 1/4" ID - 5/16" OD bronze bushings, nothing flanged but its not unthinkable some other source would have them or that a team could use some shaft collars to retain the bushing from falling out.

Of course the whole tetrix system is really based off of metric units so its possible none of this would work.

I think now in the pre-season is the best time to experiment and figure out what your team can do and try new things.

[Nemo]

Our FTC teams have used drilled out axle hubs with the McMaster D-shaft in both 1/4" and 3/8". We still had some problems with wheels spinning free of the axles, but at least the axles didn't twist into spiral shapes. We used bronze bearings in aluminum that had been drilled out to fit the bearings. It adds time and complexity, but we preferred that over twisted and bent axles.

Now that the build rules have opened up even more, we might make liberal use of hex axles.