Buffalo

With my 9V motors, I will put 2 in a locomotive and connect them together with a wire. That way if one of them loses power from the rails it will get power from the other motor. Even if my rails are dirty (which they usually are) the train runs perfectly.

First off, that's coming along really nicely and it looks like you've got some really good design ideas. Looking at wip5.jpg, the first thing I would do is replace that 9L liftarm with a 10L Technic brick, but that's my preference. Interfacing with the studs on the body would give it some extra support. Also, you're going to have a heck of a time changing the batteries in that box, if there was a way to make the rear of the machine removable so you could pull the battery box out, that might be an option. The 8878 battery box would be perfect for this sort of MOC, as you could leave the charger port exposed, or hide it under a hatch or easily removable part so you can just plug the charger in. To move the LAs back, get rid of these and mount the connectors that carry the LA driveshaft directly to the liftarm. It looks like you mounted them like that so you could use 3L blue pins to connect the liftarm to the battery box, which is a good idea, but you might be able to just use 3L pins with stop bushes and 2L axles, which wouldn't move the LAs back as far but would keep more structural rigidity. You could also make use of these, especially where the motor drives the bevel gear. It would fit right where things are now if you replace the 20T with a 12T as outlined in the next paragraph. I would also replace those 20T half-bevels driving the LAs with 12T bevels and use 12T double bevels on the LAs. That would allow everything to clear, and give you a bit of gearing down on the LA drives and allow the machine to lift a heavier load. Speaking of that, I think the leverage your LAs will exert on that 9L liftarm might bind the driveshaft coming from the motor. You might want to investigate a way to support the point where the LAs articulate. You might be able to replace those pin connectors that hold the LA drive axle with these, with the extra ends pointing down, then put a plate over top of your drive motors and space it up with plates and tiles to prop them up. As for your track drives, that machine is going to be a real speed demon with no gear reduction. If you mounted the motors side by side with the outputs facing forward, you might be able to rig up a worm-gear reduction to drive the sprockets. You can also experiment with different gear sizes on the chain drives, but the best you can do is a 24t gear on the drive axle, which will only be good for a 3:2 reduction. Whew, sorry for the wall of text.

Looking at wip3.jpg, here's my suggestion: If you have the room, move the upper motor up 1 hole from where it is. Leave the 16t gear on the lower motor, put a 16t idler gear above that, then put a 16t clutch gear on the output shaft of the upper motor, which will then mesh with the upper 16t gear. Apart from that, are you having issues with the chain drive setup you've got mocked up in wip3.jpg? If the chain is jumping teeth on the gears, it's possible that adding the clutch gear to the upper motor would help with that.

The tracks moving when the cab rotates is an unavoidable consequence of having the track power go through the turntable. As the cab rotates, it's turning the axles that drive the tracks. The way to minimize this is to have as much of the gear reduction as possible done after the drive passes through the turntable, which the excavator does reasonably well in stock form. Jurgen's Ultimate 8043 improves on this by moving more of the reduction gears into the base. The cab rotating while driving the tracks shouldn't happen, as the cab is driven by a worm gear that can't be back-driven by torque from the tracks. This effectively locks the turntable in place when there's no power being applied to the motor that rotates it. Does it rotate continuously, or does it move a bit and then stop? If it only moves a short distance, it's likely due to the slack in the gearing, which isn't really avoidable and is made worse by the worm gear drive. *EDIT: if the cab moves slightly one way going forward, then moves the other way going backwards, you might try reversing one of the bevel gear sets under the turntable. Test it to see which track changed, then flip the black reversing switch on the remote that drives that track so the controls still work as expected. If both drives going through the turntable are turning the same direction when moving in a straight line, that will try to turn the superstructure. If they are moving in opposite direction the torque should cancel out and it should move less. The one thing that really bothered me about the stock model is the large amount of slack in one of the track drives resulting from the combination of clutch gear/drive ring extension/drive ring/clutch gear that transmits power through the turntable. I replaced that assembly with a differential, which made a huge improvement but required a bit of modification to the area where the turntable mounts to the superstructure. The gearing is the same because I replaced the 16t drive gear/16t idler with a 24t drive gear and 8t idler to drive the 24t end of the diff, and the 16t end drives the original 16t gear in the track base.

They are better than the old ones, but that is still a lot of weight for an M motor to lift. My excavator has 2 M motors mounted in the boom, and the original motor was able to lift it, but I had to gear it down so it ended up being too slow. I'm now using an XL motor to lift the boom, which has no problems at all. The motor doesn't even really slow down when the LAs hit the end of their travel and the clutches kick in.

That does make sense. Since the motors that work the stick and the bucket on my excavator are in the boom, I have fewer U-joints, but I have noticed some vibration, so I will have to look into this. Another possibility, in addition to aligning the joints, is putting one or more brick, 2x2 round on one of the intermediate shafts to dampen some of the vibration. It works for big trucks, so why not an 8043? The M motors generate sufficient speed to set up vibration in the driveshafts, so a bit of extra mass might help. I will be doing some "research" later on. EDIT: I did rotate my universal joints so they are parallel. I replaced one 8L axle with one made of 2L axles and axle joiners to add some mass. It made a pretty big difference. For my bucket driveshaft, which has 3 U-joints, I made the U-joints on each intermediate shaft parallel, like: (Credit to Out of Sight for original image) The only noise audible when moving the bucket is from the motor, and it's perfectly smooth. *EDIT, again: I also took her out to play in the snow for a bit. The snow is really wet and heavy so it didn't sink out of sight right away. The treads packed the snow down really nicely, and I was able to move a bit of snow with the bucket. It also didn't get any water where it doesn't belong.

Rien, that looks great. I'm glad I could be of help I've made use of some of Jurgen's ideas in my 8043 as well. I've removed the gearbox section, and getting rid of a bunch of the gearing has made a big difference in how well things work. My R/C battery is now mounted in the bottom of the rear section where the motors used to be. I've also replaced the 16t clutch gear/driving ring assembly through the turntable with a differential. Now there is very little slack in the track drives. I'll try to get some pics after work.

For whatever reason the mention of the holiday train brought this to mind. Might be what you're looking for. I know it went great with the Christmas tree when I was a kid.

I'm running a 9.6v NiMH battery in my 8043 and have had no problems with it so far. It provides a lot more grunt to run the motors than a PF battery box with fresh alkalines, and it's rechargeable. Not knowing the specific details of the receiver's innards, I wouldn't run them on much more than that for fear of letting the smoke out. Whatever you decide to do, I've got a tutorial for making a battery adapter in my 8043 mods thread.

I've had issues with mine, but I've never built it "stock". I've added 2 extra motors to the boom, so even with my LAs aligned properly it's still got a bit more to lift than a stock model. I've also replaced the PF battery pack with a 9.6V NiMH RC car battery pack, which provides more than enough grunt to work all the functions with few problems. It still struggles a bit to raise the boom, but it works well enough for me, and it can lift a respectable load in the bucket. If the machine is on a relatively steep angle and I try to slew it so the rear of the machine is swinging uphill, the motor just stalls out. I might try swapping that motor out with a known good spare I have and see if that improves the performance. On level ground it does the spinning in place maneuver (with the tracks spinning under the machine while the superstructure stays in place) just fine, so it could be a design flaw in the model due to the imbalance between the boom and the battery pack.

I never thought about that, but that makes perfect sense now. I think the best solution would be to swap one of the grey idler gears to the other side of the LA, so they're both facing the same direction instead of facing towards one another. That way the LAs would rotate the same direction as they move in relation to the gears and once aligned properly would have precise alignment throughout their range of movement.

That 9.6V battery is probably very similar to the RC battery pack inside. It should work, assuming the cells are still good. Even if a 9V has low internal resistance, the motors should only draw as much current as they need to operate. In any case an XL motor would drag the 9v battery's voltage down so much I don't think you'd have much to worry about.

I'm working on a MOC that should qualify for this. Hopefully my Bricklink order will show up today so I can finish it up.

I actually did have a plan for that at one point, and it probably would work, but it involves a bunch of 8t gears since some of the motor outputs would have to be offset by one stud. When I started building it I had doubts that I could get it to work smoothly. Edit: I got some pictures! In this one you can see the battery pack and the power switch. The battery connector plugs are tucked underneath the battery pack itself. This battery is lime green and has LIGHTNING on it, so it must be really fast. The modified boom arm. The motor to the left is attached directly to the frames at the center of the arm and has 2 U-joints to transmit power to the linear actuator that moves the stick. The motor on the right transmits power through 3 U-joints to move the bucket. One of the motors and its driveshaft. The second motor and its driveshaft. The modified stick. It's increased from one beam wide to three, which significantly strengthens it. Imposing, no? You can see the mounts for the bucket motor and the PF lights mounted to the boom shrouds.

Soon, I'm at work now and I'll get some pics up when I get home.