True to form I started a new project, when I have so many others crying out for completion.
I have had the tracked lower section of the Bruder dozer toy from the original
ToyBash truck project lying around without any concept of what to do with it . Very recently I acquired a Wall E Truck toy on ebay and when it arrived in the post I had an idea about combining the two.
But before that I wanted to be see if I could add a drive mechanism to the Bruder tracks so they could be radio controlled. I had a couple of gear motors, another ebay find, which were were very cheap at around $12.00 (including postage from
China) and have really well made metal gears inside a plastic housing. The question was would they fit into the space available in the Bruder chassis at the correct track width. After a bit of measurement it looked like they could be just squeezed in. I built a sturdy mount from aluminium angle and a bit of 3mm sheet and then hacked away at the ABS plastic of the chassis so the whole unit could be slid into position. Some epoxy putty was slapped into the rear of the chassis and a piece of PVC sheet superglued in to the middle allowing for tapped holes so the mount could be securely bolted in place with m4 cap screws.
At 12 volts with no load they produce only 70 rpm which may be a bit slow so we will see how that works out in due course.
The Bruder dozer has molded-in fake rollers that the tracks just slide over. I wanted to reduce the friction so I decided to try and modify the track supports and add actual rolling rollers. I hacked away all the bits of ABS that were the non-functioning rollers leaving the support brackets. These were then drilled to take a 2mm piano wire pin cut with a Dremel metal cut of disc. The rollers needed to be 16mm in diameter, I had some 12mm PVC rod and then found some PVC conduit in my stock with a 12mm ID and a 16mm OD, so in my mini lathe I machined up 16 sets of roller parts. I also made the top track return roller using the original molded ABS one I cut off. In the picture below you can see the modified track support above with the un-modified version still with the non-working rollers at the bottom.
I mostly used pair of electronic flush cutting nippers to hack away the unwanted plastic along with a razor saw and much careful sanding and filing. Below is another comparison of before and after on the track supports plus the new rollers and pins.
The separate roller parts were glued together with thin superglue wicked into the join and then once set they were assembled with the pins being retained with another small drop of thin superglue, being careful not to get any on the rollers. The result has been quite successful the tracks now roll smoothly along and the friction has been substantially reduced.
The next drive train job to tackle was the drive sprockets onto the motor gearbox shafts. Conveniently the output shaft on the motors has a M3 tapped hole in the end and a 3mm hole in the shaft to take a pin. I just had to machine a hub with a slot to engage with the pin. I had already made the hubs using some aluminium rod and glued them into the plastic sprocket wheel with thin super glue and baking soda to fill the gaps. It was after this I came up with the idea to mill some pin slots, so I needed a way to hold the sprocket in the tool post of the mini lathe spinning a 3mm endmill in the 3 jaw and use the cross slide to move the workpiece, like a poor mans milling machine.
I cut a piece of thick aluminium angle and clamped it in the tool post. Then with a 2.5mm drill in the 3 jaw chuck, moved the carriage forward thus drilling a hole at the exact centre height of the chuck. This was then tapped M3 and the sprocket bolted in position through a pre drilled 3mm hole in the hub. The hub also has a 6mm hole that only goes about halfway in which is the size of the output shaft on the gear motor. With a tiny clamp stopping any rotation the slot was gingerly cut from the centre out in both directions a millimeter deep at a time for a total depth of 3mm.
This slot engages with a pin in the shaft locating it radially and axially at the correct track centre distance and the sprocket is retained with a 3mm cap screw into the the threaded portion at the end of the shaft.
Of course it would have been sensible to cut the slot before gluing the
hub into the plastic sprocket but when you are working this stuff out as
you go along sometimes the penny drops a bit later than would have been
ideal.
I have yet to wire up the motors for a preliminary test but so far it all looks like it will work.
Now with all the major mechanical issues addressed what does the vehicle itself look like, well here it is so far...
I was originally thinking of using the Wall E cab but remembered I had a 1/25 scale truck cab lying around which I think looked a lot more interesting when combined with the digging tooth from the Bruder dozer. The cab section is held on with some screws so it can be removed and worked on separately.
Some acrylic plastic wine glasses from a charity shop are being used as tanks at the rear, covered with a plethora of pipes and kit part detailing. The whole rear tank module is removable (held on with a couple of cap screws into some more superglued PVC sheet drilled and tapped M3) so the motor mount can be extracted for servicing if necessary.
I thought the arms at the side of the Wall E truck which held some wacky tractor wheels could be re-purposed for some laser like devices making this some kind of laser mining vehicle. I had a Nerf gun toy that might fit the bill for this and found another one new for only $7.00 at Target for the other side. I removed the handle which is conveniently a separate part.
Various holes in the body have been filled with styrene strip and detailing of the surfaces has begun.
More soon...
