Drill Shaft Coupler questions

[l1jmx]

Okay, we just got out drill motor shaft couplers from SPI @ $25 a piece (UGGH!). Anyways, we're trying to figure out how to make the "spring pins" on these guys work. The catalog page says there's supposed to be a hole for a 1/16th of an inch spring pin and that the shaft coupler was supposed to come with 2 spring pins. In our bag, however, were 2 pins that seem to be made out of solid metal (nothing springy about them), and they are 1/8th of an inch thick. There is no way we're fitting this pin through this tiny hole. However, in spite of the apparant failure of small parts to send us the correct item, I'm sure we've got 1/16th of an inch pins sitting around somewhere. The bigger question is a matter of how one goes about putting this pin through the solid shaft coming out of the gear box. Does anyone have suggestions for drilling out the necessary hole?

[Ken Leung]

This change happened last year when Small parts send out replacement 1/8" steel dowels to teams... Probably because the 1/16" spring pins didn't pull it off as the most stable way to keep the shaft coupler in place.

So, they send out the 1/8" pins, and tell teams to drill out the hole. Just use the original hole as a pilot hole, and drill through the drill motor shaft as planned. You probably want to drill the hole such that you are press fitting the pin in there, or else during some random time at competition, the pin will drop out and your robot will be sitting duck.

And about the $25 price... well, they are much cheaper than trying to screw a double sprocket onto the drill shaft and trust the left handed screw to hold the sprockets in place... and have them break 20 times and you running around teams trying to find replacement lefthanded screws during finals.

I really do think they are worth the $$$, since you can attach it really easily, and don't ever have to worry about them anymore. So far, I haven't heard any bad things about them. Imagine trying to attach gears onto that shaft on your own.

[l1jmx]

Okay, sounds good. Haha, yeah, hooking stuff onto the drill on our own is a pain. We were trying to get the chassis driving around while we were waiting for some of the small parts stuff. The best method I found was boring out one of the 1/4 inch id nylon sprockets we had left over since we've decided they're pretty worthless and tapping it with the 3/8-24, screwing it on, and then clamping down with the set screw. Worked well enough for a couple of the preliminary tests but I wouldn't trust it for a competition.

[tvwbug]

i have also used the drill couplers in the past with no problem.
However i have a problem i need another one, but i dont have the part number for small parts, if anyone has it could you please post the number.

[l1jmx]

PART NO. DESCRIPTION PRICE EACH

FIR-DC02* One Coupling, Two Spring Pins & One Hex Key 25.00

[Matt Reiland]

We had problems with shearing the pins on the coupling on last years robot, the tranny in low with a 3:1 reduction to the drive wheels. The best bet if you have the machining ability is to make DR. Joes shaft from the white papers.

Drill motorts? DRILL MOTORS?! - We don't got to couple no
stinkin' drill motors!

Actually we have used a specially machined double sprocket with the lefthanded screw. We never had one break, but once they are on, it is impossible to remove them. And yes - finding the left handed screw is darn near impossible.

[Ken Leung]

Originally posted by Matt Reiland
We had problems with shearing the pins on the coupling on last years robot, the tranny in low with a 3:1 reduction to the drive wheels. The best bet if you have the machining ability is to make DR. Joes shaft from the white papers.

If teams can't machine Dr Joe's drill output shaft because of various reasons, then the drill motor coupling is the way to go. The reason you shear the pins on the coupling is because there are too much load on the drill motor output shaft. One way to fix this is have another gear stage or sprocket stage, so that the second stage's shaft is taking the load instead, there the drill motor won't be taking as much load.

A lot of teams last year didn't have problems with these because they were light robots that didn't need to push a whole lot of stuff.