Russian ChTz T-800 1/16th scale Bulldozer model

[Lil Giants]

I've seen it on several youtube vids of professional operators who say "use 3rd gear & you're fired!!! Higher speeds on tracked equip equals more friction & higher temps wearing out under carriage at an accelerated rate." ...not sure how fast 3rd gear is, but could be 14kph (9.3mph).

Not a concern for this Russian dozer to travel so quick?

[Lil Giants]

Originally Posted by dozerbuilder

I personally are not too happy about the possibility of oil leaks and also having high pressure oil in the mix. I like the controllability of the RC actuators - plenty of adjustment available in the RC mixing and the ESC's.

Cheers

My Stahl 742 dozer was more than 13yrs old when I took it apart last fall, never ever had an issue with an oil leak & never needed the pressure to be that high either, just enough to lift the nose off the ground so the blade would dig in. I took it apart b/c some parts of the u/c need rebuilding.

[dozerbuilder]

Originally Posted by Lil Giants

I've seen it on several youtube vids of professional operators who say "use 3rd gear & you're fired!!! Higher speeds on tracked equip equals more friction & higher temps wearing out under carriage at an accelerated rate." ...not sure how fast 3rd gear is, but could be 14kph (9.3mph).

Not a concern for this Russian dozer to travel so quick?

Well the specs say:
Transmission: Hydro-mechanical, consisting of a single-stage three-wheel torque converter driveline and module consisting of a three-shaft planetary gearbox and rotation stopping brakes, bevel gear, two-stage final drive with a pair of spur gears and planetary row and hydraulic transmission.

Transmission provides four forward and two reverse gears.
Forward, 4 transmission ranges; 0-3, 0-5.1, 0-6.7, 0-10.6 (kph).
Reverse, 2 transmission ranges; 0-6.6, 0-14.0 (kph)

I guess it would be like any big tractor in ripped rock, slow is the go.

[dozerbuilder]

Originally Posted by Lil Giants

My Stahl 742 dozer was more than 13yrs old when I took it apart last fall, never ever had an issue with an oil leak & never needed the pressure to be that high either, just enough to lift the nose off the ground so the blade would dig in. I took it apart b/c some parts of the u/c need rebuilding.

Glad to read of your success. I like the smooth action of electric actuators all the same. Like Scranton, PA and R.G. Letourneau, I'm going all-electric.

[dozerbuilder]

Here's a couple of build pics.

One shows the frame detail. The other shows the completed sub-assemblies ready for final assembly. Of course it's been pre-assembled a hundred times prior, it was not a first-time perfect assemble so to speak. But in this pic, all is ready for final assembly. I built it in a series of sub-assemblies, it only takes 15 minutes and it's up and running. With the exception of the welded sub-assemblies, all moving parts of the model can be disassembled for repair. For example, the entire final drive can be unbolted and disassembled. I had to do that on the first field test when it sheared a 2mm dia final drive shaft roll pin.

[dozerbuilder]

Here's a link to the final field test for the big dozer. I think we were pretty well pushing it to its limits here. We wound the track speed back up a bit but it was a little too aggressive in rock so we set it back after this test finally to where it was in field test #3. Pushing leaves or sawdust or sand or dirt it wouldn't matter, in rock where we had it, it proved too aggressive. Perhaps a scientist can work this out but I think we are still getting the full 25amps from each drive motor regardless, the pulses from the pwm are just farther apart as I understand it. Certainly reducing the pwm does not reduce the torque it seems. It's been quite a brute in the overburden and rock as the vids show.



https://www.youtube.com/watch?v=nLGbWYp6u-U


Enjoy

[dozerbuilder]

The big T-800 dozer finally succumbs to field testing ripping loose rock. Appears a stone became entangled in between the bottom rock-guard rails and the RH rear sprocket while screwing the tractor. With the front idler tensioner pulled right back and the rock in between the bush and the sprocket gullet, something more had to give to accommodate the stone and it was the track links. We pressed the pins and bushes out and replaced two complete grouser and link sets. Took about 1 hour and back into service. I guess it’s far easier to replace two track link/grouser sets than twist up the final drive which can be got at through belly pan covers but is quiet time-consuming and requires roll-pins to be driven out.

The final drive seems to be immensely strong even though I’ve wound the mixing back on the Turnigy to 40%. I’m very happy with it. For those who are interested, the drive comprises 2x 25Amp (stall) car seat motors (made by Hyundai) running @3000rpm motor output speed (no load) with 16:1 worm drive reduction at the right-angle output shafts then another 4:1 reduction in the final drive which is done with 04B simplex chain and sprockets roll-pinned to 8mm dia output shafts. The drive can run at 47.5rpm full speed down to 0rpm at full motor torque using PWM. So my sprocket speed at 40% is running 19rpm which as can be seen in the other vids is about right. I also plumbed up the umbilical cord to my PC linking the 2x35amp DE dual motor ESC’s on the dozer and DE’s Describe software and used ramping to take the jerkiness out of the drive system, that’s why it runs so smooth between forward and reverse and turns.

Here’s the vid that shows the carnage.


https://www.youtube.com/watch?v=2rw9BWBx-34

[dozerbuilder]

Here's a view of the drive motors and how they are mounted. The grub screws were used just for holding the sprockets in the correct position while the roll-pins were drilled and driven in. You can see the roll pins in the larger sprockets. The motor sprockets are roll-pinned to the motor output shafts. All shafts are short and supported in bearings at each end. The third pic shows the outer final drive shaft bearing. The frame / hull is all-welded 3mm thick steel plate. Building the frame so strong in the beginning paid off handsomely later, no twisting in such a long frame and it provide a good strong base to weld or bolt the sub-assemblies to it. The entire final drive including the motors, sprockets, shafts and bearings can be removed piece by piece if necessary.

[dozerbuilder]

Here's a pic of the dozer.

[dozerbuilder]

blade sub-assemblies, ripper sub-assemblies, cab interior.

[modelman]

Very nice work!!

[dozerbuilder]

(Got a bit of time on the PC today getting ready to go to Lakeside and Brownsville and few others.)

Here's a pic of my Turnigy set-up.

The RIGHT stick operates Forward and Reverse (Up and Down) and turns, (Left and Right). Both drive motors are controlled by the one stick, mixed. For example, to affect a Right turn, moving stick to the right keeps full power on the left track while mixing reduces it on the right track incrementally from a nearly full power turn at just off-right centre to the right track fully braked #no power# at far right. I've not set it up for tracks running in opposite directions since the real machine is clutch and brakes, not hydro-static.

The blade and ripper are on the LEFT stick. You can see the blade /ripper flick switch at the top left. They are on separate DE 2x5 ESC's. So for the blade, the switch is down; this gives blade up or down, and tilt is left or right, all on the one stick #mixed).

The ripper is the same set up but on another DE 2x5 ESC.; flick the switch and the same stick raises or lowers the ripper and left or right on the same stick alters the angle of the tooth. Flick it back and you are back to blade control.