What is it ESSENTIAL to do to a drill transmission...

…to lesson its chances of failure in high-stress situations? We finally have our electrics hooked up, but when we tested our drives (wheels off the ground, mind you) we get nasty snapping noises whenever we shift from forward to reverse rapidly.

We already have the white ring (you can divine my level of technical expertise from that statement; I don’t even know what it actually is) locked in the forward position, which I gather is a good idea. However, I’ve gotten the impression that something inside the transmission needs to be changed as well, or we run the risk of catastrophic failure once we actually put real strain on the motor.

It sounds like you might not have installed the drill motor correctly.

There are two locating holes on the front face of the motor housing. It is important that these two holes line up with two pins projecting out of the face of the drill gearbox. This keeps the motor from rotating back and forth and slamming into the pins when the gearbox is shifted from forward to reverse. This rotating motion may be what you are hearing as a snapping noise.

If you do not have the pins inserted into the holes, the rotating motor will eventually break the pins off, causing the motor to spin around freely until the wires twist themselves into a knot, pulling them off the solder connections and shorting them out, causing sparks, smoke, and a popping of your circuit breaker.

We had this too…your hexical gears (worm gears) are moving on the shafts. Make some aluminum spacers to hold them in place and you’ll be ok :slight_smile:

*jeremy

Iain,

You don’t say whether your team has removed the two pins that lock the transmission output shaft from being over-driven by the load. If they have not removed the pins, the system will produce exactly the symptoms you describe, with a really nasty harsh and loud clack/clash. It may also leave the motor locked up and stalled, if you continue to hold the stick in reverse after this symptom occurs.

If you have not removed the pins, I urge you in the strongest of terms to do so without putting further crash stress on your drill gearboxes. You are headed for guaranteed headache otherwise. There are several threads in this forum that can help you with the details of pin removal.

Good luck.
Dodd

*Originally posted by Jeremy_Mc *
**We had this too…your hexical gears (worm gears) are moving on the shafts. Make some aluminum spacers to hold them in place and you’ll be ok :slight_smile:

*jeremy **

Just as a side note, Helical gears are not worm gears. They have very different functionality.

  • Helical
    – Can turn a force either parallel or perpendicular to itself
    – Can be backdriven
    – Pitch ratio determines final output of forces
  • Worm
    – Can turn a force either parallel or perpendicular to itself
    – Can not be backdriven
    – Ratio is either 1:Spur teeth or 2:Spur teeth. (i.e. a worm gear can be considered a 1 tooth gear or, depending on it’s thread, a 2 tooth gear)

Eek sorry about that. We don’t have experienced mentors, so whatever they call it I do too haha.

In any event, your gears are slipping…this happened to us and had us stumped for 2 days until we figured it out.

*jeremy

This may or may not be your problem. If you don’t have the spacer tubes in the transmission really snug, when you shift from forward to reverse you will be slamming the gears forward or back on the shaft until they stop. The Bellville spring washers were intended to be used to add a certain amount of preload. On another thread it was stated that the thrust generated by these helical gears parallel to the shaft was about 190 pounds if I recall correctly. If your spacers are sloppy, this will slam things around and could tear up the gearbox. I’m still trying to find out what the correct spacing is to use the spring washers. If too tight, they cause quite a bit of drag.

*Originally posted by Iain *
**…to lesson its chances of failure in high-stress situations? We finally have our electrics hooked up, but when we tested our drives (wheels off the ground, mind you) we get nasty snapping noises whenever we shift from forward to reverse rapidly.

We already have the white ring (you can divine my level of technical expertise from that statement; I don’t even know what it actually is) locked in the forward position, which I gather is a good idea. However, I’ve gotten the impression that something inside the transmission needs to be changed as well, or we run the risk of catastrophic failure once we actually put real strain on the motor. **

Is the left-handed screw all the way into the coupling? If it is, you shouldn’t be able to move the Al hex piece AT ALL. If it isn’t, the coupling will start to unscrew until it hits the head of the left-handed screw, at which point everything will suddenly engage, possibly causing the symptoms you describe. Note that it takes a lot of torque to get the left-handed screws down the last few milimeter, but it needs to be done.

–Rob

Well, looks like I’m going to be spending all day tomorrow taking apart the transmissions while desperately trying not to break them. I don’t even know where these left-handed screws are, let alone the pins or spacer rings and what have you. We just sort of slapped the drill motors together and mounted them weeks ago without any examination.

Our lefty screws are soooo stripped. I hope that means they are down far enoug . . . if not, well:rolleyes:

*Originally posted by Frank(Aflak) *
**Our lefty screws are soooo stripped. I hope that means they are down far enoug . . . if not, well:rolleyes: **

I think it means you should have used a new allen wrench.

PS. You get extra left hand screws when you order additional coupler sets from MMH.

Iain,

You have now received several different diagnoses of the problem you originally described, and it sounds as though you are troubled at what tomorrow’s work on the drill gearboxes might bring. Before you wail into it, try one thing to firm up what the problem is.

With the wheels off the ground and the battery disconnected, just grab one of the wheels that is driven by a drill motor and gearbox with your hands and try to rotate it, first one way and then the other. Repeat with the other drill motor train. If the drive train locks up after very little wheel rotation, your problem is the two pins in the gearbox. From what you said in your post, it sounds like they were not removed previously. If this is the problem, look at a post by Al Skierkiewicz in the thread: “Drill Motors: Pins IN or Pins OUT” in this same forum for a description of how to dismantle the gearbox and remove the two pins.

If you are able to turn the wheels by hand, then everything connected to the wheels - all the way back to the motor armature - is rotating also. Rock the wheel back and forth and observe the behavior of the couplings, gears, and everything else visible in the drive train. If gear lash or movement on the shaft is the problem, you will see it. If a shaft coupling is slipping, you will see one side of the shaft joint rotate while the other side doesn’t. You will have a much easier time of it correcting the problem once you identify it.

By the way, the left hand thread screw goes directly into the end of the gearbox output shaft. That shaft end is hollow and is tapped with left hand female threads. If you are using a kit supplied coupling to attach to that shaft, you first screw the coupling onto the right hand external threads on the shaft (REAL TIGHT), then reach down the bore of the coupling and screw the left hand thread of the screw into the internal left hand thread of the shaft.

I always found that rotating the wheels by hand from time to time is an excellent, quick, and sensitive means of inspecting the condition of the entire drive train for binding, slop, and loose or bent parts. Think about adding that step to your pre-match checklist.

Good luck tomorrow, and let us hear how you make out.

Dodd

Thanks Dodd, that helps a lot. I’m 99% sure that our major remaining problem is the pins then - I recall that the wheels can’t be rotated by hand more than a couple of degrees.