RC Tank Warfare community hobby forum

Finding gearboxes that would allow me to raise the sprockets by 2-3 mm has been a challenge for me. The Asiatam/Taigen flat gearboxes (aka dual ratio aka 5:1) fit the HL screw pattern, but can’t be raised more than about 1-mm before the large, coaxial gears rub the inside of the upper hull. Also, because the PzIV hull is so narrow, they can’t be fitted with a 380-sized motor. So, I wanted to try the Mato gearboxes. I decided to spring for the newer steel gearboxes (version 4.0, model MT-193U). The folks at MatoMart said that it would not fit in a PzIV. Not sure if they don’t know or if they don’t want to the liability of a customer using it outside of what it was designed for (designed for the HL Tiger I), but I recalled someone on this forum saying they had used them in their PzIV build. So, I took a chance and ordered a set on eBay (seller: i-love-porcelain-flower...has several Mato and HL parts). The fact that they mounted on a steel plate was also intriguing since the plate could add some rigidity to the front of the hull.

The plate was a perfect fit over the HL alignment nubs and their gearbox screw pattern. It also came drilled and tapped and with the machine screws used to hold the gearboxes to the plate. In essence it fits perfectly. Raising it will also work because the reduction gears are in a falling pattern that matches the slope of the PzIV’s front, upper hull. The only catch is that the motors were hitting the 8-pin plug when it was mounted to the points that HL placed in the upper hull between the driver and RTO’s hatches. So, I had to move the plug by installing new mounts with styrene tubing that would fit closer to the turret gear ring.
I raised the plates with 2x M4 washers that are 0.75-mm thick each. Between the plate and the washers, I raised the drive sprockets a total of 2.5 mm. There is very small clearance between the tracks and the underside of the front plastic mud flaps, but there is clearance that worked well on both the driveway and the front and back lawn. So, I’m happy with where they’re at.
With those emplaced, I can install, or position, the drive shaft supports. These are Tank-Modellbau’s setup that include bearings in them. With everything marked out and test-fitted, I can start making permanent installations of the rest of the front of the lower hull.

Note: raising the gearboxes required getting longer screws to mount the plate than came with the tank. Good opportunity to upgrade the screws to square holes, which are easier to use.

Good work Philipat, looks a lot neater than the inside of mine

Thanks.

It will get crowded fast once I add the battery and the Taigen board, speaker and smoker!

One item that needs to be adjusted is to refit the transmission covers so as to accommodate the drive shaft support bearings and the raised drive shafts. To fit over the support bearings, I used a Dremel sanding disk to sand out interior of transmission cover to make room for bearing/reinforcement. Minor adjustments could be made by scraping the inside with a hobby knife. The HL transmission cover uses two locating plastic nubs and a Phillip’s head screw to hold it in place. On one of them, I had destroyed one of the screw points on the hull because the factory had both glued it down and screwed it down. So, I figured this was a great opportunity to make it more realistic and get rid of the screw entirely. So, I made these adjustments:

- Drill out the nubs with 2-mm drill and insert metal nubs by cutting sections of an old clothes hangar.
- Drill out the screw hole using a #1 drill bit from the outside (detailed) side of the cover. From the inside, enlarge the hole with a 1/4" drill bit that sinks about 2-3 mm deep. (I’m using a 1/4" round neodymium magnet.)

- With the gearboxes, drive shaft and support bearing mounted in place, mark out the location of nub holes and the center hole. I used the forward (nearest front glacis plate) nub hole as a pivot point. Then, I found and drilled the second nub hole. With the new metal nubs installed in the transmission cover, I could lock the cover in place and use the # drill bit to mark the new center hole.

- With all holes drilled, I installed a 2x2-mm cylindrical rare earth magnet in each nub hole using JB Weld to keep them there. (Note: magnet orientation is not important in the nub holes because the nubs are steel, not magnets.)

- I filled the center hole in the transmission covers with Milliput leaving a small gap on the inside for the magnet and epoxy. I installed a 1/4" magnet in the hull side and then another one in the transmission cover, securing them with JB Weld. (Note: get the magnet orientation correct in this step or the 1/4" magnets will repel each other and the transmission cover won’t seat against the hull.)
This whole process also gave me the opportunity to glue in the styrene plates that would reinforce the front hull sides. And, I used some of the extra Milliput to fill in some of the hack job that happened as I tried to find the right spot and height for the drive shafts.
Note: before doing any of this with the transmission cover, you need to have the final position set for the gearboxes. This drives where everything else fits - support bearings, transmission cover, hole placement in the reinforcement plates, etc.

Also, I recommend doing this over several days and letting the epoxy in each step harden before moving to the next. Reinforcement plates, then metal nubs, then hull magnets (with cover magnet loosely seating to get the height correct, finally the cover’s 1/4" magnet.

Is that all ? Phew..............I thought it was going to be difficult
Great thinking Mr Phil, sure is a lot of effort for the right look eh.

I'm just catching up with your build. It is epic! I really like the detail you've put into the build and the clear progression. It's a great tutorial!

Cheers, Tom

Not too difficult, just a little time-consuming.

I'm glad it helps as a tutorial. That's my goal is to make this something that a newcomer could follow-along and do for themselves. Gets a little long-winded, but the goal is to help someone that, like me was (still is), very intimidated by the incredible work that so many do on here. Particularly the scratch builders...

Wow! How did I miss this one. Inspiring. On the other hand, had I seen it before my first tank, I probably would have just given up - quit before I started.

Thanks...glad that you like it.

I hope it doesn't discourage anyone. This is my second tank. I put this much detail into the write-up in the hopes that it will be enough to coach someone through it. Admittedly, though, it is a bit of work...probably why it's taking so long.

Only your second?!? Wow, nice work, and inspiring. There may still be hope for my brother.