New build, arduino, motomonster, 2dof

A tap from my Local Nut/Bolt supplier is also 6-10$, If you feel you need to spend 2-3X that for quality, Your sadly mistaken.

It's not so much about cost (though that in most cases plays a large part) it's more about quality and trust. Around here everything seems to be flooded with tools that will break after the first or second use and are manufactured to be disposable. I've purchased inexpensive tools that have lasted me -- many of my hand tools have been inherited or found, but lately, more often than not, without research or recommendation purchases result in a useless, broken or half-broken tool that ends up as landfill.

I have plenty of choice at hardware stores as well. Cheap to expensive.
I have been lucky in that a cheap angle grinder $20, welder $99, hand saw and hand electric drill are sufficient.
Theres a saying "a poor workman always blames his tools"

Ha, I know that one as "it's a poor musician who blames his instrument"

I didn't use tap/die but drilled an hole.
Result: one shaft broken
I'm having it welded, hoping they can fix it

So this is where I'm at now, I was planning on welding the head of this bolt to the lever and attach the pot coupling to the other side. Sounding like the popular suggestion is that I should tap the bore and use threaded rod as a shaft with bolts holding it in place instead?

A simple Pin like that will Not be sufficient. I tried Taping the gear housing with threads and using set screw's, and this is what happened after a really good jolt.



here you can see the set screw's in place.

Hrm, at first there won't be much force on my build as it's for an infant. That being said, it would be good if it was solid enough for adult usage for down the road. If tapping the bore and set screws/pins isn't the way, what is?

wait, so that last pic, the carter pin shreded the bolt like that?

No, that was to show the set screws.

That is the current cofig on the seat motor's and holding strong.

Broken coder pin was on Traction loss.

So I understand, the pin's purpose in that last shot is to keep that bolt in place, which is helping to marry the shaft to the bore and there's a matching bolt and pin on the other side of the bore on that shaft as well? In addition to the threaded bore and set screws?

The Pin in the last shot is preventing the Nut from backing off the main axle shaft. On my Seat motor's I only have the Set screw's and Single Pin preventing the Nut from backing off.


Now On my traction loss i have a coder pin doing the same thing, Preventing the nut from backing off. As well as a 5-40 x 1" that i drilled through the gear and the axle to KEY the Gear to the Axle bolt. The Picture of the messed up axle bolt is when a Smaller (all be it Too small of bolt) broke and along with the set screw's did the damage in the pic, which is part reason i suggest a through bolt vs a Coder pin or similar.

BEST case scenario is a Shouldered bolt sized to fit.

The Picture you posted with the small pin will Not work, IF your main nut backs off it will SHEAR that pin in 1/10 of a second, and will provide little resistance to the axle wanting to "twist" in the gear.

Ahh, a through bolt does certainly sound like a better option, I think I'll swap that out.

A through bolt is what broke my motor's shaft 'cause it wasn't perfectly centered. So pay much attention if you go for it

How big of bolt did you use ? The First Bolt i used was far undersized for the job being a 4-40.

I drilled a 2.5mm hole

My 4-40 that broke would measure up at 2.8mm so i could somewhat understand why yours broke as well. Although, do i expect the 5-40 bolt to be able to hold the weight if the Main adjustment nut were to back off (NOT possible when you drill the tightening nut+Axle) No. I would assume a 5-40 would snap just as easy as 4-40 with a driver in place. I also HIGHLY recommend using loctite on a lot of our Metal to metal joint's. Its only a matter of time before something rattle's loose, and loctite will just aid in preventing that.

Also remember the 4-40 I broke was on my Traction loss, So not moving a Balanced Pivot point, Its trying to throw the entire Rig side to side, and while my rig isn't a 1000Lbs, its Not exactly light with the 100's of screw's and Lbs of glue ive done over her life. Add in the Inertia that get's going with a 25:1 box on a 100mm lever arm and 4" of travel side to side. there's quite a bit of Force going on when the car in game Swaps Ends and the Rig proceeds to go all the way from one side to the other. My first set of motor "stops" Broke and they were made of steel. Motion Simply bent and snapped the screw's that mounted them.

Yep, I agree. I didn't use loctite and sometime started loosing and started playing (I don't know if it's the right word, in Italian we say play when it's not more fixed and there's some gap or little movements). Then one side of the hole became bigger and led the shaft to break. Add it was moving the balanced point, so more force, more damage...

I drill a 3.2mm hole and us a simple automotive split pin, I rather it snap then my sim get damaged from a motor freaking out.
TouchWood have not have one break yet and I flog the hell out of my sim, as in its tossed me out of the seat twice, think I need seat belts , lol.

@Blame73 yes we say play as well to discribe slight movement between two parts