870c project

[NRG]

Wow Bugle thats looking great with some great machine work You was on about a top brace before, if your making this yourself have a look at the yr4 m2 as i think it is a design you could use and it looks ultra cool too.

is that the kind of thing you was on about ? if so i have a brand new tensioner(the silver springy bit) i will gladly donate to this project

[Bugle]

Yeah Jason I machined the pulleys, I still have to make the side things to hold the belt on.

NRG nah wasn't thinking of doing it that way. I was thinking of making just a rear tensioner with a solid turnbuckle going from the top deck to the bulkhead cap, but i've decided to just leave it as it is with the motor mount holes slotted for tensioning the rear belt. I'll make a whole one piece top deck with an idler pulley arrangement attached to that for tensioning the front belt.

[Bugle]

Almost finished the thing, this is the finished centre slipper & pulleys setup, turns out the front belt is so tight with the top brace I don't need to worry about a tensioner

I made all four suspension arms from delrin, the front arms are the same as original rear arms without the toe in angle on the outer holes. Rear arms are 870c at the inner end then made longer to suit later offset wheels with 1.5 degrees toe on the arms and 1.5 on the RC10 hub carriers.

Found that RC10TC3 steering knuckles have exactly the same geometry as the original magnesium ones, but they take imperial bearings. So i'm running 1/4" ID bearings all around with custom CVA axles which go 1/4" through the bearings then step down to 5mm for the wheel adaptors. B44 front driveshafts ended up being the right length for the front, I made some custom driveshafts for the rear.

Made new shock towers out of carbon fibre and a top brace out of fibreglass (still have to etch the copper off the other side), rear tower is screwed into the rear bulkhead cap, front tower is braced to the bulkhead cap through the balljoint mounting holes with some angle aluminium. Had some bottom loader 0.71" shocks lying around so I switched to those on the front and made the tower higher to suit. Still have to rebuild the shocks though.

For mounting lipo batteries I bent up these copper trays, was pretty easy to make them. Not sure if I need the extra weight though. For the rest of the electronics it's got a Mamba Max, 5.5t motor, KO Propo digital servo and the Corona receiver which I still have to mount the antennas properly.

[Toasted Coastie]

Thats pretty slick man!

[Mr. ED]

can you explain a little how you made the double slipper pad work on the original shaft please?
(I don't own a B4 and have no clue on the dimensions of the parts involved)

[Bugle]

I had to make the shaft from scratch on the lathe, goes 5mm through the bearing then steps down to 3/16", the inner plate & pulley is pinned to the shaft and I milled flats further out on the shaft to take the standard outer B4 plate, from there out it becomes a copy of a B4 shaft.

[Alex B]

Is that a MR4 BX slipper plate with pulley used on your Yoke?

[Bugle]

Nah I machined that part aswell. Does the MR4 BX one have the same number of teeth? I didn't know about the MR4 BX setup until after i'd made this one, that would've been easier to use if they're still available. I also wonder if the MR4 BX pulleys would fit the 870C outdrives.

[Alex B]

The Mr4 BX slipper pulley is almost an exact fit. I have tried it against the yz10 slipper centre shaft and although it dosent fit it would be possible to make a custom centre shaft that would allow you to use the upgraded slipper, you then make the shaft to use either the centre one way or older centre slipper assembly.

I have a spare MR4 BX slipper I could lend to you if you want to try it.

[Bormac]

Thomas I cant wait to see this going! Let me know when you want to go for a run and I'll bring the Digi SLR out to shoot some of the action.

[Bugle]

Thanks for the offer seasaw but I should be ok to just use the one i've made already, it won't be too hard to make another if I wear it out. The wide diff pulleys were the worst part to make, with so many more teeth to mill out, if MR4 BX ones could be used instead that would be good.

Jason i'm probably gonna give it a run this weekend at the St Ives meeting, if it all goes good i'll race it at the Maitland interclub

[Bugle]

Had a test run today with the 5.5t, it was pretty insane, seems to get the power down way better than the B44, the acceleration out of corners was so good. Never heard the belt skip either. Only problem I occasionally did a wheel stand which ended up bending the wing up, and one of the lower front king pin screws fell out. I'll go with a 5-40 thread on that screw next time..

I think I need to put proper servo mounts on the servo, it seems to move around slightly on the tape which can't be good.

[Toasted Coastie]

Had a test run today with the 5.5t, it was pretty insane, seems to get the power down way better than the B44, the acceleration out of corners was so good. Never heard the belt skip either. Only problem I occasionally did a wheel stand which ended up bending the wing up, and one of the lower front king pin screws fell out. I'll go with a 5-40 thread on that screw next time..

I think I need to put proper servo mounts on the servo, it seems to move around slightly on the tape which can't be good.

Had the same problem with the king pins on mine. I used some medium strength threadlock to keep the lower ones in.

[Bugle]

Yeah threadlock would work alright on the magnesium ones, I would've thought plastic would be ok without it. The thread is stripped now anyway so I'll just go with the bigger thread and hopefully it ends up tight enough to not come out.

[Toasted Coastie]

Yeah threadlock would work alright on the magnesium ones, I would've thought plastic would be ok without it. The thread is stripped now anyway so I'll just go with the bigger thread and hopefully it ends up tight enough to not come out.

turned outthemagnesiumones onmine are stripped as well. Looking for "new" ones now....