Just wanted to start a thread for any questions, feedback, suggestions on this year’s first choice offering for the Bosch motor PN 6004 RA3 194-06. I work for Bosch in the motors division so I am familiar with the technical details on this motor. Also, I’m currently an FRC mentor and have been for the past 15 years (wow how time flies).
Hopefully teams find this a useful addition to the motor options. It’s best for a quick addition without much worry about custom gearing and fits a pocket in the options where you might want more torque than the window and snow blower motors offer. Of course at a cost of speed. With a build in thermal switch it is very unlikely to make magic smoke or destroy itself from overheating. It also has an integrated hall sensor which can be quite useful for position feedback and to give the programming teams something to play with. It’s good to see this option becoming more common in many of the KOP motors.
Some of the other Bosch teams had some initial samples to experiment with so may be able to share some early ideas on how best to utilize.
Interfacing with the start output might be the biggest challenge. Wish we had a hex output:o . Thoughts about 3d printing an interface has been brought up but needs to be experimented with since it may not be strong enough. Another option is if you can find or mill a square 6mm x 6mm steel or Aluminum shaft…or even mill down a hex shaft. It’s very important that you have a tight fit since any slop with slowly start to strip out the connection and once that goes it’s very hard to repair.
I think this causes this motor to fall into a bit of a utility gap. Teams that have the ability to use the star output shaft may find their resources better suited to implementing a more powerful non-backdrive solution or integrating a sensor in a different design.
Last year, Team 20 actuated their forks by installing a BAG motor to the Window Motor gearbox with an encoder integrated between the BAG output shaft and the worm. More power, included sensor integration, and honestly not that much more difficult than dealing with that star output shaft.
Lower resource teams may be scared away by the star output, it is not easy to interface with at all.
I think if this had a 1/2" hex output you would have a lot more interest from teams. One application that comes to mind is the window motor shifters employed by Team 67 (I think they ditched that when they started using pneumatics?). The slow speed won’t hurt you, and the added integrated position feedback might make it simpler to integrate.
Agreed. It’s why we opted not to include in the rookie KOP as the second low volume option. Maybe good for a medium resource team as I think there is a fairly simple way to mill a square interface into a hex shaft with a little patience. It’s not a star but it gets you part of the way to an optimal solution.
We received our first two samples of this motor last night and they looked very promising for light loads. I had a whole bunch of questions for you but then I realized most are answered here:
One question remaining after reading the specs: Is it possible the output power curve is on an incorrectly labelled axis?
Example:
If you look at the peak power point at 11 N.m, the Input power should be 13V x 6A = 78 Watts.
The output power curve shows ~14W, and doublechecking torque & RPM confirms it at 13.8Watts
I don’t expect high mechanical efficiency from a worm drive, but ~18% seems way off. Can you check and/or clarify? (Or correct me if I missed a unit conversion or decimal place.)
Regardless, it looks like a nice, light gearmotor option and the hall effect sensor makes it extra useful over a window motor. The challenge as you point out-- will be the relatively fragile output drive material, so that’s a problem for us to solve. Square drive looks like an obvious solution, but more contact area would be better. Can you point us to a specific vehicle usage? We might be able to scrounge junkyard parts for the proper mating 8-point shaft. If the junction has survived automotive durability testing, it has a good shot at surviving FRC duty (if properly applied).
Are there any COTS 8 point shafts available? If not, what would you suggest we use? We don’t have the machining capabilities to make one out of metal. My first thought was 3D printing, but testing would need to be done to see how much stress a 3D printed shaft/hub could take.
This interfaces with quite a number of GM seats. It’s a long list so I’ll try to dig that out. It is specifically used for the recliner function in the power seats. I may have a few of these star shafts laying around that I can send if I find enough…maybe cut into pieces. I’ll also see if we can find some scrap at our Tier 1.
Regarding efficiency I too was a bit surprised but that’s what comes out of our dyno measurments. Actually too much efficiency is a problem in seat and window applications in that you don’t want movement as the car bounces about on rough roads. In this motor there’s a worm and two stages of spur gears for ~179:1 gear reduction.
CAD model for the motor can be found at link through AndyMark. I should point out that there was an error in the first posted model which is currently in the process of being updated. I’ll let you know when it is updated.
Have you tried drilling out the star pattern at 3/8" and broaching a key or a 3/8" hex?
This motor seems like a good choice when you would like to use a hobby servo motor, but need much more power (and have a home position sensor). The biggest issue I see with this motor is that it can’t support any load on the output. In FRC we love to abuse our motors and gearboxes by hanging way too much weight on them.
Do you know if these will be available from AndyMark after First Choice is over?
Last year’s rule says “The mounting brackets and/or output shaft/interface may be modified…”. It seems like that modification would be covered by that wording.
Internal gears are all plastic except for the worm. Hard to predict absolute limit since a lot depends on how well it is mounted and how tight the fit to the shaft and if it’s a quick or slow force acting on it. These plastic gears will take quite a bit of abuse but something will crack or strip if lets say you have a long lever arm and smash into something.
We have a metal gear option but it was so heavy we decided not to offer it.
I did find a few options in a mechanics toolbox where the square part fit exactly. It was a non standard fitting though. Might take a little digging but it’s out there. That is a good option for a quick and simple solution.
I do have a 3/8" rotary broach and may give that a try. I think it might take too much of the wall out though.
You definitely need to mount this to a completely supported shaft since that acts as the output and second support. If you use the motor to support the shaft then you will most likely have problems.
We decided to offer in limited amounts to get a feel if teams will use them. If there is enough demand then we may be able to consider another order. This is a high volume production motor so it’s fairly easy to order more if needed.
We received our first 2 motors yesterday. It looks like the internal star pattern will also accept a 6mm square key (I measured 6.05mm). Oversized key stock (+0/+0.08 tolerance) will probably fit nicely (in stock at McMaster-Carr). I’m also thinking about modifying a 1/4" bore AndyMark hub to accept the 6mm square. Thoughts?
The reason I suggested putting a wrench on the output of this motor, is because of the speed at which it rotates. There really isn’t much use for a shaft, is there?
