"Doggy Bag" YZ-834b runnner build

[olfrjf]

Well done Dadio

little video now? we will see in action...

[Dadio]

I will post a video but i have no realy good camera so it will be phone or tablet footage .

[Dadio]

Slowly getting it dialed in , I've got the slipper working well the diffs are still breaking in but I've tightened the rear diff up a bit and it's more predictable to drive now , next is to loosen the front diff a bit .
I have one more minor issue with the chain tensioner , I solved the clearance on the top deck by cutting a little notch in the top deck but now the tensioner moves up so much under breaking that is hits the front of the body and pushes it up , the body is only velcro'd down and it just pops off at the front , I've cut down the top of the tensioner bell crank , reduced the height of the tensioner mount and moved the body forward a little as the slope of the body gives more clearance but it's still doing it .
I'm tempted to fit a body mounting post and use a body clip to hold the front , otherwise I'll have to do a redesign of the tensioner system , not sure what to do

[jwscab]

just limit the tensioner adjustment range. you could probably do away with the spring and just make it an adjustable length with a turn buckle.

[Dadio]

just limit the tensioner adjustment range. you could probably do away with the spring and just make it an adjustable length with a turn buckle.

That's a really good idea , thanks I'll give it a go .

[Dadio]

I just fitted a turn buckle or at least a threaded rod with ball joints ,it worked a treat ! Thanks again for the idea .

[jwscab]

[Mr. ED]

Dadio, you did it again! Amazing dedication and skills.

[Dadio]

There's still stuff to do yet , I want to have another go at the idler gear to try and make it wider so its fully engaged with both gears , even the 1 mm lack of width bugs me but I have a solution in the pipeline , then she could really do with a new dress , I'm thinking of the Funco style body but I'm skint till pay day so that's got to wait .
Then it's just wait and see how totally outclassed it will be by my friends Cat XLS Re Re ........ I think my only hope lies in his tight fistedness , he doesn't want to spend a lot (or any) on electrics so he's planning on a transplant from his Kyosho RB6 RTR , so a sensorless 10.5t basic ESC type system and a slow servo , I'll have more grunt (and need it) ,better brakes and more responsive steering , he'l just be half the weight and have a huge handling advantage .

[Dadio]

Grrrr I screwed up making a part , I had two acetal gears that I was trying to make one wide gear out of by locking them both to an axle shaft , I'd cut back the boss on both gears to make the right overall thickness and off set , I'd turned up a shaft and knurled it in the middle , I'd aligned the two gears by using to other gears meshed in to keep them straight and I'd pressed the shaft into the gears but just 1 mm too far so I was just pressing it back the other way and one of the gears cracked ....... 3 hours waisted and on broken gear ......crap day.

[Dadio]

I had the first apparent failure today , the front diff came appart while driving , on inspection there was no damage it had just come loose from the drive spindle to the right wheel , the diff is held into the spindle with three grub screws and I think I'd forgotten to use thread lock on them as they had all backed out a bit , if I made the part again I think I'd make it a threaded joint locked by the three grub screws rather than just a sleeve and grub screws but it's back together now with no damage , it also gave me a chance to inspect the out drives for any wear after 5 battery's of running and there is nothing to see yet so all's still good.

[Dadio]

I got a little Video clip made , just after I'd cartwheeled it spectacularly its got a ticking noise on cornering in the Video due to a bent dogbone at the rear .... easily fixed.
[youtube]https://youtu.be/H4aZ7CIzEGg[/youtube]

As you can see she's plenty quick enough

[Dadio]

Now I have it running well I need to start looking at its weight , my stock Dogfighter is 1388g the new one is 1624 so 236g heavier , a diet is in order .
The chassis material is just plain heavier , the front suspension is all alloy and the rear trailing arms are solid acetal with alloy hubs .
I can definitely reduce the weight of the trailing arms without compromising their rigidity by a few g .
I don't want an overly perforated chassis plate but I'm thinking I can mill sections down from 3mm thick to 1mm thick leaving it clean and flat underneath , I can perforate the top deck as it's not needed much for structure .
The front top arms are rather over designed and could be milled down a bit .
My solid alloy rear gearbox guard could lose a lot of weight .
Even adding all this up I think I'll be lucky to loose 50g ! I'm not sure where else to look for weight reduction ?
I guess adding 2 shocks ,alloy front suspension and a fibre glass chassis is going to have some weight penalty's but I was supprised how much !

[Mr. ED]

You should leave the chassis alone. It helps to keep a low cg. Back in the days the minimum legal weight was 1.7 kg drive-ready.
With todays motors esc and lipo technology the extra weight wont hurt.

[Dadio]

Thanks , I like the way it looks now , I don't really want to perforate it and I have no real hope of keeping up with a Cat XLS ..... Not going to stop me trying though