Gauging Interest in Affordable COTS 20DP Racks

I’ve done some work sourcing a supplier for custom-made 36" 20DP 14.5PA aluminum racks for FRC use. I started looking for these because most COTS racks are A, steel; B, over $60US per foot; and C, solid, requiring teams to manually mill and tap mounting solutions.

I’m looking at three options: solid rack, rack with side holes, rack with side holes and tapped bottom holes. Prices look like they would be $30, $40, $50 respectively, plus shipping. The distance from the side holes to the pitch line is 0.25" and the overall pitch height is 0.5". Face width of 0.5". Holes are placed every inch and appear to be consistent between racks, meaning you could stack multiple racks next to each other with no issue. Total weight is 0.82lbs, compared to roughly 2.5lbs for a steel rack.



Would any teams be interested in something like this? I could look into setting up a vendor to satisfy BOM rules.

38 Likes

I don’t know how frequently we would have use for it, but 4911 probably would have purchased and used a length of it this year. We used a rack section on the end of a pneumatic as a brake mechanism for a gearbox.

3 Likes

Yes, please. This is a great product with an obvious demand.

1 Like

Appear to be? If this is a feature you are going to market, you should be tolerancing this on your drawing.

Anyhow looks cool. How are the teeth cut in this?

3 Likes

Looks interesting, we would probably buy at some point (game dependent).

It looks like, on your drawing, the side holes are 5mm. This is close enough to 0.196" (clearance for #10 fasteners) that we wouldn’t need specialty fasteners. What size/thread pitch are the bottom tapped holes?

Actually they don’t appear to be 1" spacing either as 50.8mm is 2 inches. Unless he’s saying that they alternate faces at 1" spacing.

1 Like

4253 is based in Taiwan and uses mostly local parts, so the holes are tapped for M5 bolts.

There is some type of hole every inch, so I was indeed saying alternating faces. On the racks with only side holes, the holes are spaced 1" apart.

M4 might be a better size, as it’s not as easily confused with imperial bolts and already exists in the 775 class motors. M5 is a bit of a risk for me.

2 Likes

I spent probably 8 hours this past season perusing through every available rack gear under the sun that could see use in our robot. Not satisfied with the strength, availability, weight, and especially cost, we ultimately moved in a different direction in the design. But, I could definitely see the application, and this price point sounds rather reasonable.

You can buy cheaper rack than SDP from KHK, although they’re metric module rather than inch DP. A 1m (39") length of 1.5 module steel rack with holes costs $150 USD, so you’d beat that price. https://www.khkgears.us/catalog/product/SRFD1.5-1000

I am usually not a fan of aluminum gears, but I can imagine an FRC rack wouldn’t see very many cycles, so you might get away with it (although look into getting some kind of coating).

So short answer - yes, could be valuable!

2 Likes

+1.

1 Like

+1 Interested. I recall acetal (or nylon?) rack gears also being used (e.g. 3339’s climbing stalks in 2019)… That might be another option for an FRC COTS supplier to consider sourcing and distributing.

1 Like

I could imagine several scenarios over the years where we could have used this. Definitely interested.

Very much interested.

Definitely would be interested especially at those price points. Can at least be used as comparative option/prototype.

Used ~10 ft of steel rack on our 2019 bot so we’d absolutely be interested!

+1 here

Yes, but not for FRC purposes.

Is the material 7075? Are you planning to coat them?

I agree that the tooth phase needs to be controlled so they can be stacked end-to-end. It we be best if the phase of the tooth at both sides were symmetrical and aligned with a tooth root.

I think I would be interested in these for really high load purposes and for home made CNC equipment.

4 Likes