Are the 12 tooth metal pinions essential on a robot? We don’t have any and want to double up on the smaller plastic 12 t gears instead. Is it worth it for us to get pinions?
I wouldn’t say it’s required but they would work better than plastic. But it also depends on the situation your using them in.
We want to use them for the arms on 448X style arm
Also, we are going to use two motors for the arm because it is heavy
Are you using V4 or V5?
we are using V5 motors 100 rpm
Well, the plastic gears are prone to breaking if the load is particularly too heavy (our team learned that the hard way last year). The metal gears are not, but they do need an adaptor if you are going to use low-strength shafts (not the kind for wheels).
You should also try to use as much aluminum on the arm as you can to reduce as much weight as possible.
Oh ok. Will we need high strength shafts if we use the metal gears?
You should use an adaptor. The high-strength shafts will fit into the motors, but will not fit through the metal piece.
The old metal pinions have been discontinued, which only featured a hole for regular shafts. The new ones can be used with regular (adapter) and high strength (no adapter) shafts.
Are high strength shafts needed to supports large amounts of weight or do the small ones work fine?
Depends on how much weight and the design. Honestly high strength will just work better in general
If we want to save cost, do 4 regular shafts put together give the same result as HS?
Seems a bit overly complex and a waste of resources but if it’s all you got go for it.
Yeah, we’re about to order parts again and want to get just what we need.
we are ordering more aluminum as well
I’m just wondering, r u part of a school team or unaffiliated? If ur unaffiliated I can understand that, but I think that if the school really wanted the team to succeed, they would pay what is necessary as long equipment is not asked for frivolously.
Unaffiliated and we don’t have a sponsor. We’re just splitting the cost between everyone
No, the results are not the same, although it might function OK. Here are the two issues:
First, a bundle of four shafts, when twisted, will slide over one another, so you will not benefit from the increased ability to transmit torque. If you want to study this concept more, you can look here: https://www.engineeringtoolbox.com/torsion-shafts-d_947.html You only get increased torsional resistance moment when the shaft is solid.
The next problem is the shape of the shaft. The VEX shafts are not actually square, but rather a square with cylindrically-rounded corners. This allows the shafts to be driven by the flats, but also to rotate smoothly in cylindrical bearings. The sketch below helps explain this, and shows that if you bundle four regular shafts, the corner radius does not match the HS shafts; therefore, the shafts will not turn properly in bearings. You might be able to jam the bundle into a motor, or through a high-strength plastic gear, and certainly through a high strength lock bar (which has a square hole), but its unlikely they will fit through a 12-tooth metal pinion gear.
In that case, I recommend just getting a hs shaft. 4 axels together won’t sit the hs bearing properly.
Edit:Just realized @kmmohn said the exact same thing