Blackjack build - Cobalt puller + VF dig = mods!

[ecoli]

I just started my own Blackjack build over the weekend. I've been extremely impressed with how well this chassis has performed for others, so I decided to build up one for myself. Build details:

Chassis: Blackjack
Tires/wheels: Proline badlands, Ace's memory foams, MSD top guns (Axial offset) with weight added.
Shocks: Traxxas GTR Revo aluminum with Jato springs (yellows)
Axles: Axial with all the rcp goodies (aluminum upgrades, straight axle, etc.) and Freakstuff Racing steel lockers
Transmission: Axial with VF dig
Motor: Cobalt 7t puller
Electronics: DX3r tx/rx, MM esc, CC BEC
Links: Homebrew. 8-32 allthread sleeved with steel brakeline. Revo rodends. Lowers are Axial bent link length, uppers are about 4" long I think.

On to some pics:



As you can see, some significant modification took place to get the transmission and motor mounted using the stock skid plate width. I've cut off the supports on the motor side plates (more on that later) and rounded off the tips at the shock mount locations, as I found the tip was just scraping against the shock caps. No problem with that now!



To help strengthen up the motor side of the chassis, I cut a new skidplate that runs the entire length, countersunk the outermost holes (originally intended for the lower links, but I'm mounting those in further) and bolted the skid plate to this. I had to countersink to ensure that the links cleared this bolt.

Now each side has four bolts holding it to the skidplate. I actually have plans to further strengthen up the motor side, but that won't happen for a bit.

And now a few more general shots:











When I mounted the upper links to the inside, it became apparent there was still going to be clearance issues, specifically for the pinion/motor shaft. I will be shimming up the tranny (not as much as in the picture, driveshaft angle is way too severe currently) to ensure good clearance. Everything is going to be very tight though, the driveshafts just clear. As long as nothing moves....

Still have to finish setting up my dig. I didn't realize until I put it together that the long set screw is 4-40, and all my hex drivers are metric. Off to the store I go.

And yes, I've got a lot of crap hardware on it right now. Switching it all over to button head M3 hex drive, once my supply comes in.

[binaryterror]

I had a hell of a time getting my stock Black Jack skid to fit a AX-10 Trans, VF Dig, and a Taller 55T lathe motor. I ended up making a new lower skid plate which allowed me to add in Dual Triangulation.

[ecoli]

Originally Posted by binaryterror

I had a hell of a time getting my stock Black Jack skid to fit a AX-10 Trans, VF Dig, and a Taller 55T lathe motor. I ended up making a new lower skid plate which allowed me to add in Dual Triangulation.

Link? I looked for a build thread, but couldn't find yours.

Yeah, the things you have to do when you stray away from what a chassis was originally designed for! None of the mods were really time consuming. A dremel and a file make short work of aluminum!

Everything will clear with the shim in place (luckily for me, someone posted a pdf with the tranny bolt pattern ;) ), but just barely. I may flip the direction of the driveshaft side upper link bolts (locknut on the outside, bolt head on the inside) to give it just a mm or two more of clearance.

[Tanis]

Looks good ecoli Only thing I have done to reinforce the motor side plate on mine, besides adding a custom full length skid plate, was to drill one more hole in the middle of the opening, and run another buttonhead there. I haven't had any issues with my chassis, and I've been driving it since Jan.
Looking forward to you getting it finished

[binaryterror]

ecoli: Never got around to a build thread...assumed it was typical. Now I see the need though...Just a simple plate...nothing fancy like I'd like obviously. Worked well this past weekend, 3rd overall in 2.2.

I'll post up a build thread so people can see it. But I want to get some Delrin links on it for the lowers at least! lol.

[ecoli]

Tanis: Thanks, yours and Kamikaze's build and video threads were what made me decide I had to get this chassis! If the additional bracing mod I have in mind works out, there will be no need for another hole drilled in the chassis. Will see what happens with the buil.

BT: No rush, I've seen the other double triangulated skid plates before, so I've got a good idea of what you mean. Always good to have other options in mind though, in case the current set-up doesn't work out.

[Tanis]

I just looked at your pics again, and realized you've got 4 screws on that side, so you shouldn't have any issues.....don't know what I was thinking

[ecoli]

Progress is slowly moving forward! Shimmed up the tranny with a few pieces of thin lexan and bolted it on, added all of the electronics and some cross braces to help solidify the chassis further.

The dig just needs a bit more fine tuning, hence the dangly bits hanging out underneath

On to the pics:





Lots of wires. The receiver is buried under there somewhere! Good thing the SR3100 is so small, no way you'd fit a TQ3 receiver on here.



High clearance (3.5") and still solid as a rock on its side.



Shaved the one rod end to allow clearance for the set screw on the pinion (I hate RR pinions, but they didn't have any Losi 12t pinions in stock!).



One question I had is with the placement of my BEC. I just ziptied it to the battery lead from the esc. I don't think it would produce enough heat to cause a problem, but if I should move it, someone let me know!

[ecoli]

Got everything running tonight. The dig works like a dream. A little patience was needed to get it set-up right, but so far it seems to do fine with the little 225MG servo. The cobalt 7t is an amazing motor. The torque this thing puts out is amazing. I swear when the rig got bound up, it just wanted to either crush the rock or my wheels!

A couple of questions though:

1. As above, is my BEC ok where it is? I've never run it in warmer weather, so don't know what kind of heat output it has, but don't want to melt my motor wires.

2. The one problem I ran into was the rear driveshaft slipping on the dig output. I've tightened it down and added threadlock. Anyone else experiencing this? Any quick fix?

I really wish the outputs on the Axial had a drilled through hole like on Stampede or Rustler outputs so you could run a longer set screw all the way through. I know some have done this themselves, but drilling through hardened outputs isn't exactly my idea of fun.

As long as I can get this issue sorted out, I'll be able to give the rig a real beating this weekend to see how it performs. The quick test tonight though seemed very promising!

[Tanis]

No problem with the BEC mounted there, it won't get hot enough to hurt anything, if it does, you have other/more important issues

[JUSTGOINGSLOW]

I'm running the Revo shocks on my new build also with the 0.7 yellow springs. And they seem to be working pretty good, what weight oil are you using? also I cone pointed my output and pinion shafts, so the set screws stay tight.

[ecoli]

Originally Posted by JUSTGOINGSLOW

I'm running the Revo shocks on my new build also with the 0.7 yellow springs. And they seem to be working pretty good, what weight oil are you using? also I cone pointed my output and pinion shafts, so the set screws stay tight.

Yeah, um, about that slipping driveshaft, turns out it was user error/stupidity The dig wasn't fully engaged into 4WD, hence the slipping under stress. I had to adjust the endpoints slightly to make sure it was fully engaged. Everything works good now, but still a good tip if the driveshafts really do give me issues.

As for the shocks, right now I'm just using the Jato 0.7 yellow springs and stock oil. Will have to do more testing to see if it needs to be changed.

More work to do on the rig tonight, we'll call them touch-ups. Big test will be this weekend out on the rocks. Oh yeah, still have to mount these badlands. Wrist workout coming up!

[JUSTGOINGSLOW]

Cool I;m glad to see everything working out for you. A little FYI, this weekend I'm going to remove the powder coating off the Jato springs, and then bake them at 450 for 30 minutes to soften them. I'll let you know how it turns out.

[ecoli]

Got out in the backyard this weekend to do a bit of crawling. This rig performs incredibly well. The cobalt motor lives up to all the hype, and the dig worked flawlessly. I was setting up rocks in all sorts of stupidly high vertical positions and the rig was clearing just about all of them. Only issue I had was a "high" speed runaway when one of the battery packs got low.

As you can see, I added a bolt on tuber for it. Finishing up the painting on the frame today. Still not sure if I like bolt on tubers, but it was cheaper than buying a lexan lid

It's based loosely on this rig. which I'll probably use as the design for my rockracer :

[ecoli]

Few updated pics with the painted tuber and panels on.