The Slightly Depressing and Boring Tale of MotherLoader T-34

 MotherLoader Is Dead. Long Live MotherLoader!

This is a chronicling of the last of the Loaders. I am pretty sure that the prior version with the dual weapons is undocumented on here but it has a decent showing on FaceBark and the BBB forum so I'll leave sleeping dogs lie as too much time has passed. To be fair, the same could be said about this version as it's over a year old since it was built, fought and forgotten but as of Feb '25 I have pulled it out to have a look over so to keep things fresh I'm plastering the build up here too. 

It's mostly ripped from my BBB forum post so if you've read that chances are you're unfortunately familiar with my musings. 

The old was gutted and the corpse paraded in front of the prototype of a new. 

It looks quite simple all spread out and I’m inclined to make it simpler. I’ve fallen out of love with the little forklets and will change these out for a moderately sweaty single fork in the centre of the wedge. I planned to beef up the wedge to about 10mm too just to continue with the tanky theme. The lifter will be jettisoned for ease too.

MotherLoader T34 will be a quick and dirty rework with the aim of getting something ready for BBB in February 2024. Brutal and simple. And yellow.

Progress on ML-T34 is going well as it doesn’t actually need much designing. Things are mounted where is most convenient for them and I have given up the battle on trying to compact and condense as I feel it is often a detriment to function. This robot will be wide and ugly. This robot will work. Confidence! We love it.

The drive required no modification to type. It still retains the 32DP RC car pinions driving a spur gear built into the driver pulley. There are simply two of them now. Oh and they’re brushed. Klaus was phenomenal to drive and the amounts of brutal power on tap were exactly what I wanted. The speed of Klaus was a problem but this is less of an issue as I am running a smaller effective wheel diameter and there is an additional reduction slapped on there too. Torque city, Population: Me. The pulleys are nylon, the gears are 7075 alu and the bulkhead has been sloppily test printed in ABS for now before committing to nylon.

This is the finalised but unfinished weapon system. While looking super similar it has been almost completely retooled with lots of quality of life and tying up of engineering loose ends. The most obvious difference is with the weapon motors. There are simply two of them now. Still a Nerf mod motor shoehorned into a 22mm rotolink planetary gearbox but now it has a twin. I figured it adds a little more redundancy and doubles the power (funny how that works) The axe self righted wonderfully but it will be borderline lifter territory now. Maybe some hook and grab attachments are dancing, mockingly, just beyond the horizon.

There is no longer a big combo gear as it was a massive weak point. Simple but horrible to change out and work on. Also the first stage which is only MOD1 was distorting in nylon and straight up detonating in PLA-ST. Instead it is going to a metal gear - I have a hardened 40t RC car pinion which is potentially overkill and heavy. If I can’t lighten it I will change out to a 7075 aluminium one. The benefit of using an RC pinion is the 5mm bore which means I can just switch the whole transmission over to a live shaft, running a length of silversteel through bearings in the bulkhead. Hot swapping gears has just become incredibly simple.

The second stage is MOD1.25 and the gear has a 12mm hex bore through most of it. Hubs with a 5mm bore and a 12mm hex are incredibly common and cheap so one of these will be pinned to the shaft and make these gears (which are rarely damaged due to the pitch and massive face width) easily swappable too. It has cut the amount of fasteners that need to be removed to work on it by about 75%

I do plan to run both these motors off a single ESC and really stress test the BBB current limiting! Though for once I have the space to add a second should it prove necessary.

The other prominent feature of the new weapon module is the repurposing of Klausforx which are 8mm Hardox and will sit slap bang in the middle of the robot. They will ride on a 6mm pin, though they are currently just sat on a bolt while I wait for the postman. They are rotation limited so they can’t fold underneath and I hope to have the traction to pluck them out from any wall gaps I get them wedged into.

I have made an amusing (frustrating) mistake which rather boils down to forgetting that magnets are magnetic and that permanent magnet DC motors have magnets…permanently

The right hand fork, if pushed all the way up will stick fast to the can of the Nerf motor. This in turn will lock the axe from completing a full swing. This is what we in the trade call “A Bloody Silly Mistake”. I am in the process of drawing up a little TPU bump stop that will cushion the impact and restrict the upwards travel to gain back some semblance of my dignity.

Downside of doing everything properly and not cutting every corner imaginable is it turns out pretty heavy. By the time I have that steel gear and a shaft in there I will have doubled the effective weight in the weapon system - this should be okay as I had wiggle room with the limit before and I have cut a whole weapon system out of the robot already - not to be ignored.

This subassembly just got a lot heavier. I had a smattering of Chinese parcels come all at once so I made really decent progress with the weapon system.
First and foremost was the 6mm silver steel shaft and collars to replace the random M6 bolt the forks ran on temporarily. It’s much nicer having something smooth and solid for them to sit on and the collars keep them nicely spaced and stop them from kinking too much and sticking or wobbling.

The gear turned up too, a chunky hardened steel 40t MOD1. It’s actually a pinion for a 1/8 RC car which affords me a usable 5mm bore and a narrow face width. I designed up a lasercut gear and had it interfacing with a cool hub then gave up and spent the six quid on two of these that do almost exactly the same thing. Downside is the weight as it top my scales at 45.5g. Meaty!

Naturally a gear with a 5mm bore needs a 5mm shaft so I printed myself a little jig to batch produce a couple easily. Just slip your rod inside (calm down) and you have a easy locator to file the flats on and bop two 2mm holes centrally through the shafts.

But Harry, I hear the masses cry, have you gone mad? Have you lost the plot with one foot out the door to go live under a bridge and eat glass bottles? Why on earth are you drilling holes through your damn shaft you handsome rebel. 

Arguably the answer is yes I have, but to follow the more pressing engineering question it is to use pins to drive these 12mm hex hubs from 1/10 scale RC cars. Pins locate them axiallly as well as transmitting torque. One should be enough so in keeping with the theme of this robot I used too.

These are stacked up and pushed inside that thick printed nylon gear and it feels pretty solid.

This is the stack up of components outside of the frame to illustrate where the bearings are and how much is going on in quite a small space. One of the best parts about all of this is it’s pretty much all off the shelf. I like the challenge of not relying on a custom designed part. The hunt for something that would work and all interface together is really satisfying.

And then all together! Ready for some transmission tests. I’m also going to be doing a little bit of delicate angle grinder surgery on the small pinions and the 40t gear to nip the facewidths down.

I got the motors bolted in and all the transmission components set up so I could test this. It was at this point Gareth (BBB's resistant electrical wizard) pointed out the neat endstop feature of the v3 BBB esc I was using on the weapon. This really would help with retracts and not damaging anything. With this in mind I printed a rear panel that has a micro switch mounting point and cut a chunk of 3mm HDPE to be a baseplate.

Here you can see it in the retract position. The switch has a little bit of foam heatshrunk (heatshrinkeded?) around the lever as a bit of compliance while I get a TPU bump stop finished.

Next up I pulled my finger out and started making armour. I printed a template in ABS and set it up on my ghetto router table. I screwed the pattern to the part using the mounting holes which worked well. Honestly it feels like such a cheat code for making plastic parts. Only downside is the mess and sometimes you get a chatter-ey finish. 

Not too shabby by any stretch of the imagination. Not winning any prizes for sure but it's nearly on the level of shitty desktop 3018 routers for pennies on the plastic dollar. Quick and dirty wins the race. 

Then I swapped in a 45 degree router bit to put the angle in. Much quicker than messing about with a hand plane like the MotherLoaders of old. Came out quite well to be fair. The front armour is 10mm HDPE which should be plenty for taking the abuse. I don’t intend to make spares I made the other half in the same way, just taking care to reverse the chamfer. Get a look at the absolute width of this chap!

My word what a wide, busy little nugget. It was truly immense at this stage and I was slightly regretting my decision not to smallify everything to the nth degree. Something seems very vulgar about a large robot. I miss the MK1 for that level of size and simplicity. Perhaps I should go back to making wedges. I had the proof of mobility deadline approaching rapidly at this point so I frantically got it to a drivable state. 

Despite the unbearable weight of massive girth it was remarkably tight inside - extra tight considering there are some very pinchy bitey bits of transmission slung right next to tightly packed wiring.  The tightness inside and being tighter on weight than I liked left me with the decision to ditch half the drive motors. I *really* wanted 4 motors as it fit the design brief of rugged, ugly power. Klaus was fantastic to drive with 4 of those motors on 4s but I let myself take the easy way out by harking on the simplicity angle. More space inside left me with less jam packed components and less chance of overheating, crushing or pinching. 

Luckily two is more than enough, but it is a bit of a failure on my part. I am proud of the fact I know my limits better these days and wasn't foolish enough to plough ahead to really sink that damn cost. Cut your losses, kill your darlings and dry your goddamn nylon. 

So it was about a week or so until Brawl so I was entering the “lots, but none at all” stages of progress. Most apparent is I cut out the 10mm yellow HDPE I am using for the sides. These are functionally identical to the old version but once the profile was cut I added a chamfer just for a bit of flair and to chuck out an extra couple grams. Produced once again with the 3d printed router template technique. I think they turned out really well for a handmade (technically) part. Just adds a little extra character to what could be just a rectangle with a 45 degree chunk out of it. It has two M4 screw inserts where it bolts too the wedge but otherwise is held with the shoulder bolts and two M4 countersunk bolts.

Also pulled my finger out and cast the new tracks. They’re 30a once again with a TPE core as it seemed to work well. I printed enough cores while I had the material loaded to have 3 pairs worth of spares. First time for everything! Now I can charge into spinners with even less fear. You can really see here how much better everything sits with only 2 motors. The battery has room for padding and no wires are smushed up against bulkheads and components. 

Finally managed to get my nylon back to a good place and was able to sort out the last of the big prints. They had to stay together while I finished up the mechanics and such. Now that that is out of the way it’ll get stripped down and dyed a healthy glowing yellow. Once it is suitably jaundiced it will be time for final assembly. Pretty happy with how it all came together. I made a lot of good progress with my time management and crisis control so I finished a functional robot early. 

When life gives you lemons etc. I did the classic yellow dylon bath for the printed nylon parts and it came out pretty well again. I’m looking forward to doing a robot that isn’t yellow so my hands don’t look quite so jaundiced/nicotine stained after fishing them out. Honestly I think this step is why I have a lot of luck with my nylon prints. Nylon loves water and that gives it a lot of flex. The warm water dye bath is absorption city and they come out so pliant and flexible. Not at TPU levels, they're still structurally stiff but I really like the properties and it really works for my design. 

I started doing final assembly at this point, putting in the proper loom and mounting up the end stop micro switch. The axe mechanism goes together and comes apart really well. Traditionally I don’t have to touch it so by the law of sod I’ll have to strip and rebuild every fight. All the wires run across that back board of the robot. Technically the only big spans are from the RH drive motor and the battery itself that get routed through the slot feature in the bulkheads - lots of clearance for an XT30. 

For the first time ever in 3 versions using the same piece of hardox ML is sporting some edge. Ground the axe head so it’s at least sharp. Still not deluded enough to think it’ll do anything but it at least looks like it’s trying and justifies its own sharp edge protection. 

Not to indulge too much in self congratulatory wankery but I adore this subassembly. It's so delightfully bitsy. It is almost wasted in a lumbering tracked shell. Add in some Beta/Terrorhurtz style folded polycarbonate and steel and it could be a lovely little chopper. Ah well. I'll just entomb it in chunky matte plastic lumps. 

Found another late stage wobble in the design. I went up a tooth on my drive pulley and that caused it to clash with the boss of the pinion gear. Not enough to notice on the model or at first glance but you definitely felt it clicking as you turned it by hand. I had to ghetto lathe (drill & file) it down and it was unbrilliant but functional. 

Done! ish. This is pretty much as good as it got. Completed and underweight with days to spare. I am writing this off as a success from the goals I set for myself. Simple, driveable and rugged as I can build it. I genuinely think it is the best it can be with the parts I have, the methods I selected and my ability to design *this* specific robot. It might sounds like that is a lot of conditions and concessions I made for myself - and that's because I have.  The whole aim was not to reach too high or make it into something more special than it needed to be. It wins my criteria purely by existing.  That might not have come across like I mean it, I haven't articulated it particularly clearly. 

Last run-around before the competition! Drove super well and was responsive enough. I split the weapon off to a separate transmitter as I found that incredibly helpful. I drive on an I6 and my wife is on axe duty on the GT5. 

As is customary I snapped a picture with the shell of the prior version which was also coming with me to Bristol as a stop on it’s way to it’s new home. You can see T34 is a touch wider and fractionally longer thanks to the forks. The chassis profile is identical all the way back to MK1. 

My first fight was against Digestive and The Mangler. Two polar approaches for naming on show here. I was a little on the back foot to be the only non spinner but it was quite nice in a way. What a way to put the robot through it’s paces! Cards on the table, I wasn’t too worried about Mangler as while it had the potential to get to the thinnest armour I felt confident I could avoid getting into bad situations and I could overpower them from a drive point of view. Digestive was the real worry.

I was correct to be worried. Verts get a fearsome reputation and that’s one I feed into myself but not all are created equal. The speed of the drive and the sheer anger in the weapon meant I could not keep up in any meaningful way and just became a bit of a chew toy.

I take a slim moral victory in the fact that I was able to keep soaking up some really nasty hits without really suffering. The lights stayed on and everyone was most certainly still home. The HDPE stood up well and I’m glad I went for 10mm everywhere.

The worst but was arguably the baseplate which had been hole punched and had a substantial trench carved just shy of the important bits. Taking it off the robot I found it was badly warped. Cutting the smushed parts away seemed to remove the internal stress in the part and let it go from Pringle shaped to flat-ish. I was a little miffed at the track had come off as I was completely willing to keep going. I think it was just impact related though I’m not ruling out stretch.

I had a cup of tea and a scotch egg to steel my reserve and got on with mundane activities like charging batteries and bemoaning my now slightly wonky (ier) chassis.

I was then told I was fighting Tsukikage which was a bit of a downer for me. I do not do well with control fights. This robot was 4wd with lots of forks and pokey bits to get hung up on. I wasn’t realistically able to overpower him nor out drive him. I think potentially I had the speed advantage but not the wherewithal to make use of it.

We were a pretty even matchup with no quarter given either way in the battle for control. Meg was going absolutely buckwild with the axe which caused the front to jump a little on a miss but I think ultimately turned the tide as we landed more hits than we didn’t.

A loss and a win was a pretty good place to be, until I found out I’d drawn Andy.

I always tend to do a quick function check when I’m back to my table after a fight. Just blipping drive backwards and forward and seeing the axe twitch is enough for me. I did this post Tsukikage and all was well so I slapped the battery on charge. A little while later I picked up the robot to show or demonstrate something and found the right hand track had locked up completely and would not be back driven. Odd. I plugged the battery in to check further and was immediately greeted by thick white smoke and an unpleasant smell. It was like being back in school.

I just went head down and swapped the whole unit out. Thankfully ML is pretty easy to chop and change out components so it was a pretty easy fix. It was only later trying to run through the steps in my head did I hammer out a working theory.

-intensive driving fight causing a bit more heat than I’m used to
-scratch that, a LOT more heat. Enough to soften the epoxy of the windings.
-when it’s still hot it works just fine. Once it has time to cool, say the time it takes to charge a battery it has cooled and the windings have now set so they’re touching with no coating left on them.

Motor locks up, just waiting for a drop of current and then boom. Toasty.

I am willing to entertain other theories but that one seems to fit. Glad I checked as I would have looked like a monumental tit. Swaggering up to the arena, turning my robot on and having it immediately let out a sad cloud of smoke and stop working. Bet that would have gone down well with the marshals.

ANYWAY,

The Propane was pretty short and brutal with me failing to get any footing once again and just resolving myself to tanking hits and trying to outlast Andy in the hope he broke his hardened fist on my wobbly yellow face. Unfortunately the repeated abuse knocked the track off but I was in a position to wiggle onward, soaking up a few more hits before a nasty hit to the rear took out the link door, power light and link. Smashing the rear panel in the process. Dead in the water, it counted as a tap out but it was lost either way I just saved having to count to ten.

So that’s it. Finished as I started. The first version was what really got me back in to robots. I made something pretty rubbish but functional which a bit of flair and I have been chasing that ever since. I made a lot of mistakes and errors trying to recreate the purity and effectiveness of a weaponless wedge.

MotherLoader-T34 was designed to work. It was supposed to be brutal and hardy and be controllable. I took every step I could to make it reliable and drivable and honestly, this was pretty successful. It wasn’t the nicest looking or the most interesting thing I have built but I figured I had to take a step back. If I keep failing to make interesting and clever work for me, dumbing down to stay in my lane is a valid strategy.

I’m happy it got one win, with my low bar for success that’s pretty good going. At least over the last two years I haven’t gone backwards and that is no mean feat.

I have it firmly planted as being the last of it's kind. For over a year it has sat in the same condition as it came home from the event. The reason this post has been written up now (13 months later) is I relented and cracked it open. I have been working on some pretty cool stuff (Hard Nips and a new Klaus) but I yearn to just have a plug n play damage sponge. 

I made the false assumption that as it was working it was ready to go. This was pretty much an error. It's going to need a fairly large shakedown in order to be anything other than a display trophy. I'm sidestepping my rule about this being the last one by just kind of fixing it rather than redesigning anything. 

My shopping list so far involves 
- making new tracks
- fixing the axe 
- neaten and simplify the internals 
- link replaced with a switch 
- making the drive more robust. 

These are all fairly low effort high reward so I'm pretty on board with actioning these quietly in the background. I feel I owe it to the lineage to have it at least as a backup beetle. Watch this space!