pic: 1156 Off season Fisher-Price gearbox

Just assembled this gearbox designed by our team. We’d like to thank Metalúrgica Diedrich and Máquinas Kehl.

It looks simple, robust and effective. How long has it been since FP motors have been legal?

In 2012 you could still use some FP motors, we’re using them because we had some spares. Since we’re using those for an off season project, just for the sake of learning, we decided those were ok to use.

Also i’m not completely sure right now, later i’ll have a look if the am-9015 fits the gearbox. Since the gear distance is adjustable you could use other motors with the same mounting holes.

Why is the gear distance adjustable? That will seriously lower efficiency and reliability in high-load applications if it’s not done correctly.

Perhaps to use different combinations of gears?

Agreed. It looks like they have a slotted hole on their motor mount. It will be very difficult to adjust this to within a few thousandths of an inch.

It is better to be too far away than too close. Once you get more than a few thousandths closer than C-C, gears will wear really fast.

I get that, but how is it implemented? That’s actually more my question, as it really depends on the implementation.
Also, you can still use different gears with a fixed center distance. For example, if you have a 12t to 60t gearset, you can replace it with a 24t to 48t gearset without changing the center distance.

Exactly my concern.
Talke a look at how 192 adjusted the belt tension on their gearbox this year. They used different mounting points for the motor to vary the distance to ±0.05". You can make easily 5 different center distances with this method.

looks like the gear is plastic, would it shear in a pushing match?

I mean, if you make a drive base using only fisher-price motors, and then try to have a pushing match with another drive base, then I suppose breaking gears could be one of the many issues you might run in to…

I was just thinking that…
in all seriousness, any high-load application for this should utilize current sensing just in case IMO.

The gears inside the “stock” FP gearbox are plastic. It looks like the 1156 actually used the first stage gears straight from that here.

The FP motor is an air-cooled motor (like the AM-9015 and the BaneBots motors). If it stops spinning it loses its cooling and burns up very quickly. This is also the first stage off the motor, and this motor does not generate a lot of torque off the shaft (high speed, low torque). The motor will stall long before the plastic gear strips, and then you let the magic smoke out and that lovely burnt motor smell fills the air.

Offseason on CD is filled with so many drivetrain ideas and prototypes that we tend to forget not every project that gets posted is for a drivetrain. The output of this gearbox is far better suited to an intake or shooter wheel than it is something like a drivetrain.

Correct me if I’m wrong, but I seem to recall that FP motors had face mounted vent holes, so an improvement to this gearbox design could be to add openings in the plate to allow air to flow through. (unless you have them and I just didn’t notice them in the picture, in which case, props to you)

You got the right idea. We did in fact use the plastic gear from the FP gearbox to simplify the design and avoid having to produce a gear since in our lab we don’t have the necessary tools and so we’d need a sponsor to do that for us. This gearbox is designed for high speed and low torque applications, for example shooting or collecting game pieces.

The gearbox was designed as part of a project to build a budget robot that would play the 2012 game, since we felt that we didn’t perform well that year and it would be a good learning experience. We’re focusing more on learning how to better design game mechanisms instead of focusing on designing a new drivetrain since we feel that the drivetrain we have fits our budget well and has enough power already, so having a better scoring mechanism would help us more. When the design is completed i’ll post a render of it here on CD :smiley:

Good thinking there. Yes, they have those vent holes and we could have even opened some space for them, yet i don’t think that we could do much, since they are close to the holes and with this adjustable design and thin plates it the area around the mounting holes could get a little fragile if we opened too much space for ventilation.

Over the years we’ve made a few of our own FP gearboxes, for use in applications where the motor is not likely to stall. That means, powering a roller, not an arm. They have worked well, and we didn’t make them nearly this fancy. The cooling holes are a good idea. The motor location needs to be set by the mounting hole for the motor pilot (the large area around the bearing, on the end plate, just behind the gear), and not by the mounting screws. The screws are just too small to be able to hold things in place on their own.

Good work, and it’s a really neat project!

The gear distance is adjustable so we can use different gear ratios with this gearbox. Yes, that’s true, it would be less reliable in high-load applications, but we designed this gearbox for high speed applications, like shooting and collecting game pieces, so that is probably not going to be a problem.