RC Tank Warfare community hobby forum

My Mod for the drive sprocket and shaft.

Hi everyone, thank you for your interest.

Excellent Dongskie, that's what i had in mind.



Continuing the build with the suspension and roadwheels



Following the successful prototype, i am setting up a small assembly chain. Preparing the outer tubes for holding the suspension arms on the chassis. These are made of 4mm brass tubes, inner 3mm. I did cut the brass tubes using a hobby knike new blade rolled around the tubes while flat on a surface instead of using a tube cutter. I found that tube cutters are not sharp enough and usually crush the tube a bit, creating problems when overlapping tubes are required. This process ruins the blade of course but i usually purchase 100 of them for about $25 online so this is not a real problem and it saves a lot of trouble trying to fit the tubing.


The holes for the torsion bars on the chassis are enlarged with a new drill bit and the outer tubes are installed, permanently glued in place. It is critical that these holes are enlarged correctly, they must be strait and horizontal with the surface. Otherwise, the suspension will not be strait.


The mount for the suspension arms are 3mm tubes. There are many different wall thickness and brands of tubes. It is important to ensure that the ones selected are overlapping with a tight fit, while still being loose. A lot of cleanup and sanding are usually required at the both ends following the cut.


The suspension arm mounts are made and a slot for the torsion bar anchor to stick out at the tip is made using a Dremel cutting disk. The slots are made in 2 minutes and do not require perfection, these will soak in epoxy anyway.


I am installing a 1.5mm thick torsion bar on the two frontal suspension arms under the gearbox. This is to ensure the weight of the gearbox, battery and control board will not give the suspension any issue.

However, the rest of the vehicle will be very light so i am installing smaller and more flexible 1.2mm thick torsion bars under the other 8 suspension arms. These are also made from metal tie/push rods available on eBay for a few dollars, available in different sizes and length.


The Takom plastic torsion bars are glued to the suspension arms and then cut at the base. It fills the hole at the base of the suspension arm for the next step. Then, a 3mm hole is carefully drilled in each suspension arm. Use a new drill bit for that. Again, it is critical that the holes are drilled strait and in the center, as much as possible.


A small groove needs to be made for the torsion bar anchor to link it to the other groove.


The tips of the mounts are dipped in 5 minutes epoxy and inserted into each suspension arms to ensure optimal solidity because the torsion bars are also what is holding the suspension arm in place.


Before the epoxy glue is completely set, the metal tubes are cleaned up of any residue using a blade, also creating square corners for a perfect fit against the chassis. They are then let to dry overnight.



While the torsion bars are drying, the roadwheels are prepared. It would have been really nice to have rubber band tires on these roadwheels, it would have simplfied painting as well. Instead, we have to glue the two plastic halves with a lot of sanding required for a smooth finish. I know i will have to do a lot of corrections on the seams later.



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Roadwheels inner and outer halves are ready.


Suspension arms and torsion bars are polished and given a final check.


Torsion bars are cut at the calculated lenght.


Each of the suspension arms are tested and given their most perfect mates on the chassis. With such suspension design, there are always small imperfections in the alignment that can be mitigated by selecting two components that mitigate each other.


The torsion bars are anchored on the bottom of the chassis after being given a plasticard base. The angle of the suspension arm is grossly calculated and the torsion bar is bended inside the vehicle. This is a critical step. The screw positioned at the tip of the bended torsion bar is what is holding the whole suspension in place.


Each suspension arm horizontal alignment is finetuned by twisting the torsion bar one way or the other using the suspension arm. Each component are solidly in place. This needs to be done prior to installing the roadwheels.


The inner roadwheels are positioned. Notice that the suspension arm has a hole in the middle. I decided to make use of it.


The tube holding the roadwheel can be held with a screw instead of being glued. This will allow for maintenance.


Self tapping screw assortments are available on Amazon for a few dollars. I used the M2 x 8 but had to cut the tip a bit.


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Another amazing build

Inner roadwheels are installed. The screw is not completely tighten, ensuring the roadwheels can turn loose.


The outside roadwheel is glued on top of the inner roadwheel with only a few drops of superglue each, ensuring the two halves can still be cracked open for maintenance purposes, if ever required.


The frontal compartment and the interior floor are dry tested on top of the suspension. Some adjustments are required where the support for the floor were touching a torsion bar or their bases. The space between the bottom of the hull and the raised floor is extremely limited for an RC vehicle. The design worked.


The model as it stands today.


Next step; the gearbox, sprockets, idlers and tracks. Then some test runs...

Regards, Louis

Awesome Louis!!!

Hi everyone,

continuing with the sprocket.


The Takom sprocket interior is quite hollow and weak. The center cover on the outer halve is extremely thin. Looking at some selected material, It took me an hour to analyze and determine options and select one, keeping in mind the scope of the project which is to create a simple light conversion to drive the vehicle around.

A M3 metal hex bolt matching the size of the hole on the coupler is used. After the bolt was inserted from the other side, the interior of the sprocket was filled with epoxy glue to give it some structure and solidity, and ensuring the shaft is strait as much as possible, otherwise it would have a wobble and that would be terrible.


The sprocket transmission cover is a good base to hold the sprocket because the small tamiya gearbox itself is not solid enough, it is not a regular metal RC gearbox where the sprocket can be mounted directly. There are for sure many ways to make this work, this is one of them.

Before final assembly, a metal file is used to flatten an area on the bolt where the small hex bolt of the coupler is located. This will ensure a strong connection.


The couplers are installed, as tight as possible with the sprocket cover.


I had to drill a small hole on top of the sprocket cover in order to tighten the coupler hex screws. These holes do not show as they are on top, under the fenders.



After making sure the gearbox shaft is fully all the way into position inside the gearbox (it might have moved), and after thoughout calculations that will allow the gearbox to be installed and removed for maintenance, the right side gearbox shaft was cut. In case of uncertainty, it is better to cut the shaft too long than too short, and adjust later. The gearbox is inserted inside the right coupler first at maximum lenght, then the left side enters the left coupler, and the gearbox is then positioned in the center, allowing both shafts to fit the first solid section of the couplers, and then the screws are tighten. I must have done this 50 times.


After a lot of dry testing to make sure everything works, the sprocket covers are glued in place.




My hex bolts were a bit too long, something to watch out for. Either replace with shorter locking screws or remove some plastic material on the front cover for the coupler to turn without hitting it.


After a lot of dry fitting for the best position of the gearbox inside the allocated space, i selected to create a thin inclined base at the bottom of the chassis, just above the torsion bars. And i also gave a thin plasticard base to the gearbox itself.


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After a lot of testing, the gearbox is installed. It is held in place with a few tapping screws holding the base on the gearbox on top of the base glued to the bottom of the hull. The built-in mounts of the Tamiya gearbox were right above a torsion bar and could not be used.


The gearbox is soaked with synthetic Permatex grease.



Moving to the tracks.


At first, it does not look like there is a lot of tracks but there is. One track has 63 links and the other has 64.

It is only once you have cleaned up and assembled a couple of prototypes, calculated how long it took and the problems encountered, that you realize it will take about 10 hours of work to complete both tracks...

I saw that Takom is only providing a handful of spares, maybe five or six links, without ability to get more. Better not screw this up or the build is in jeopardy without purchasing another kit.


Tracks sections are cleaned up, taking 2 hours.


Takom had to put a sprue connection right on the lips...


Encircled is the partial track pin given by takom, the rest is completely loose. It should be enough to drive the vehicle around. The assembly is difficult and there always seem to be residue to cleanup.


This is the part that goes on top of every link to close it. Need to put some superglue at specific areas in a specific amount without spilling over, and then drop the part strait on the link below without shaking or misalignment, which would likely spead glue on the pin and ruin the track link. After each track link is put in closed, i always had to constantly go back to the previous 15 links to check that everything was still flexible and loose. If i saw that a link was about to seize up for some reason, it meant some glue had spilled, so i quickly had to crack open the link before the superglue is completely dry, clean it up and safeguard the link for another attempt.


After 4 hours of work, the first track is finally ready. I wasted 4 track links so far, mostly at the start, i have only 1 or 2 spares left, i think. I got better at it after the first half.

While building the track, if your fingers start shaking or being sticky with glue, it means it is time to take a break. Trying to go fast assembling the tracks will be disastrous.


I decided to put aside the other tracks and install the idler to do some tests on the first track.


The idler base has an internal void that was filled with a plasticard plate.


Idler mounts are installed.


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The idler adjuster is obviously static.


The interior of the idler wheel is quite simple, just room for a plastic tube to lock the inner halve to the plastic shaft. I have analyzed the situation for a hour to see how it could be improved with the use of metal tubings, ball bearings or else. Any solution that i had to improve or reinforce an area was just weakening another. It would be risky to try to do too much with so little plastic involved. I therefore decided to use the idler as it is, but just to make the wheel removable for maintenance.


The base for the Idler is hollow and the connection to the idler arm is quite weak. Takom has the builder glue the idler arm on top of this mount without supporting structure.


However, this area can at least be reinforced with metal tubing without any risks.


It gives more strength to the idler arm when in position. This is not a working idler adjuster, the idler arm will still need to be glued at the proper position after the tracks are installed, but the idler arm has more support than before. I tried to put a small screw in the hole in an attempt to make a working idler ajuster but the bolt head interfered with the idler wheel and the plastic everywhere is just too thin. Everything on the M113 is small and tight.


The idler hub was removed, and a hole created for a tapping screw that will link with the idler arm inside the idler wheel, keeping it in place and removable for maintenance. This is also required to install and remove the tracks because the situation at the sprocket does not allow it to be easily removed.


The first track is installed, idler arm is glued in place, ensuring a nice slope for the tracks. Looking good. The position is different that what Takom had calculated for the static little arm that adjusts the idler.


I will have to remove 1mm from the static idler adjuster before installing it. Maybe my suspension is a bit higher but any tighter than this and the tracks would likely break.

Looking at Vietnam era pictures, we can see that many M113 suspensions in the field seem to be overloaded, sometimes very low or almost crushed.


I could not wait for the second track to be completed before testing the tracks with everything else. Tests were made at different speeds, without pushing it to the maximum. So far so good.




Next step is to complete the second track, and then do some test runs

Regards, Louis

Absolutely incredible workmanship!