"Doggy Bag" YZ-834b runnner build

[Dadio]

I have ended up with a few left over parts for the venerable Dogfighter YZ-834b , some parts i made , some CNC parts that I've swapped out for genuine and a few that came as a bundle so i have surplus , I was tempted to sell a few bits but looking at the pile it sort of started to look like enough to get started another car from , then a few more bits popped up on eBay and that sealed the deal .

I'm not looking at a perfect car here , more of a runner , I'm starting to get a bit protective of my already complete (ish) Dogfighter . I'm planning on bringing it on a bit , wider , longer ,belt drive , slipper and hopefully a front diff if possible , 4 shocks etc and probably a Brushless system .
All the new parts will go onto my existing car and the older stuff to the runner .
Never thought I'd have a shelf queen ! its kind of never been a thing for me but my existing car may end up retiring !

[Dadio]

Right progress so far .
1 Transferred the new gearbox and genuine lower front suspension arms to my original car .
2 Made a hybrid ball diff from a genuine diff gear and balls and Team C diff out drives and thrust bearing , this means that any wear will be to modern replaceable out drives and modern shafts .
3 Fitted scorpion Re Re stub axles and bearings to the rear suspension arms as well as the 12mm hex conversion parts , these give almost another 20mm to the width and allows modern wheels to be used .

So far I've only sourced the diff gear and the second gear with shaft for the rear chain sprocket , however the idler gear between these gears is a plain 20 tooth gear so this will be replaced with a pair of pinion gears to make up the width needed . The spur gear or first gear is more tricky as its a reduction gear with both 46 and 21 teeth , however I'm planning on attempting to make a slipper clutch made with a 21 tooth pinion and a spur gear , probably a modern 48dp gear of a very similar diameter to the original , again this will mean any probable damage or wear will be to a modern easily sourced part .
I've now got a nice sheet of 3mm GRP to make an extended chassis , the old doggy is about 30mm short by modern standards , i don't want to go that far as its going to look obvious but i think 15-20mm could be done by moving the gearbox and trailing arms further back without too much visual impact .
Anyway a few pictures of what i have so far.

[Peakey]

Looks like a good start, I’m waiting on a chassis to start mine off that’s going to be a runner. More details on the rear diff and the slipper I was looking into having something done but I’ve still not had chance to pull mine apart to really get it sorted yet.

[Dadio]

The rear diff was a lot easier than I thought it would be , I have an old Team C TR02V2 that I was using as a spares car so I nicked the diff out of it , the center of the Yokomo diff gear has a 9 mm hole and the support bearing on the team C diff was 8 mm so I made a 0.5 mm thick sleeve on the lath (outer 9mm inner 8mm) out of plastic , I used the Yokomo ball's and then just assembled it. Next was the gearbox bearing on the diff ,it's a 12 mm inner 24 mm outer , the out drives on the Team C diff are 10mm so again I made up a pair of aluminium sleeves that I secured to the out drives with green locktight , the only slight difference is that the original Yokomo diff has a spacer to off set the gear to one side of the gearbox inline with the other gears but the modified diff sits centrally , this is not a huge issue as the idler gear ( small 20 tooth gear ) that it is driven by is the full width of the gearbox .
I'll post up some pictures later .
The slipper is still in my head but will hopefully be a combination of a repurposed diff gear as a spur gear , a 21 tooth pinion gear and a set of turned down Team C slipper plates and pads on a custom made shaft that will exit the gearbox through a hole drilled through the gearbox inside one of the bearing supports , hopefully it will have an adjustment nut and spring next to the motor to the rear on the gearbox side , the trick will be to make it all thin enough to fit inside the gearbox .

[Dadio]

A little more progress , last night i made up a new roll bar , that was a little frustrating as i had two bars of aluminium the same measurement and one was a hard alloy and the other soft but i forgot to label them so i obviously chose the wrong one and it snapped on ... you guessed it the last bend anyway i made another with the right bar and it came out better than the one i made for my first dogfighter so i swapped them over .
This afternoon i cut the chassis plate adding 5mm at the front and 10mm at the rear to extend the wheelbase by 15mm overall , i had fun attaching the vacuum cleaner to the jigsaw , i had to do it because i had a mask on and the dust was covering the cut lines , it was a bit clumsy but not too bad , overall im quite pleased with the chassis , still needs a little more cleaning up but not too bad for a first attempt .
I've also added a few pictures of the hybrid diff .




complete diff with sleeved out drive .

not a great picture but you can just make out the black sleeve around the bearing.

[Peakey]

It’s coming along great! I’m now itching for my new chassis to arrive so I can start mine and the belt conversion I’m looking into. I’ve also been thinking about a front diff of some sorts and I’ve seen an old photo today for a mod on the rear driveshafts

[Dadio]

I saw in another 834b build thread on here what was thought to be a front ball diff but it was decided to keep the build stock and the diff was NIB and no very clear pictures through the bag so I got no clear idea of the design of it .
I have ideas but I'm stuck on how to make it strong enough while passing through a 5mm inside die bearing , I'm really tempted to drill out the front bulkhead to 12mm so I can fit 6mm inside die bearings then I'm sure I can make it work , it's just a bit non reversible .....with a very rare part .......

[Peakey]

I’ll send a front box off to my mate and get him to draw it in cad then we can either have one printed or milled I thought I had already sent one off but I just sent the rear arms, mounts, rear brace and the front knuckles.

[Dadio]

I'll take 3 knuckles and a front gearbox please seriously !

[Peakey]

I said I’d send him one to draw but he said I’ve been watching one on eBay so he bought it

[Dadio]

Cool .

[Lonestar]

Resto-modded 834b... where will the creativity of this board's member ever end that's absolutely awesome

[Dadio]

I had a first attempt at a shock tower for twin shock's up front , its freehand and not quite symmetrical but i can sort that on the second one , not sure weather to stick with GRP or use CF instead (i have both) for the second one , it does work well even if its slightly pissed .
I also made up an idler gear for the gearbox , its a 1/8th scale 32dp with a 5mm bore so perfect for the 5mm shaft the bearings take , its actually the second pinion that i ordered , the first was exactly the same on paper but it was a machined gear and looked a bit harsh to use on stock plastic gears , this one is a Traxxas (pause to spit) one and looks like it was forged or stamped but either way the gear teeth are far smoother more polished and should be less abrasive to the plastic gears , its not quite as wide as I'd like , there's about 1mm on each adjacent gear that's not meshed so i also have some plastic gears coming that are half the width but i should be able to link two together to get the full width so , well i don't know witch way to go yet but this gear will work for now.
Oh the rear shocks are only temporarily mounted in the picture and will not be that way eventually .

[Peakey]

This is really coming together fast! One of mine has the alloy front twin shock tower I’m undecided weather to keep it or revert to the mono shock. I’ve ordered a couple more bits for mine yesterday too and can’t wait till my chassis arrives.

[Dadio]

Ive kept my other one mono shock front and rear and thats the way its staying , it even has a good non leaky original front shock , i have a rear shock thats ok for a shelfer but its leaky and so worn it jams .
This new one is so non original that anything goes , the front and rear shocks were both in my spares box so are ripe to be used .
So how much of my original plan has been realised .