OS's CFX Killer

[OSRC]

I'm building a "test course" so I can compare Apple's to Apple's. Fun project... hoping i can dial rigs in right in the backyard so i dont have to load up everything and drive out to my local crawl site all the time.

[Natedog]

Originally Posted by OSRC

Paint and decals done finally. Holy cow, does this thing take some time to decal up.. Since I'm running TLT's and a Tamiya body, decided on a modern Rough Rider theme.

Drive-wise, it has a very low COG with the motor hung as low as possble so it's pretty stable.

Using the RC4WD t-case as overdrive gave far, far too much OD to the front wheels. Was literally dragging the rear end up and over stuff. Sometimes that's good, but I had no drive at all in the rear, so the front was doing all the work. That's no good. Motor was super hot after just a few minutes of testing which I hope was due to the axles fighting each other. Going to remove the OD and just set it up as a std. t-case

Compared to a newer kit, the steering on this is just laughable. BUT it is fun to wheel regardless. Still needs sliders and think I'll finally break down and paint the chassis.

That looks great! Love the double GRU type transmissions, white wheels go well too! As you said fun to drive!


I haven't done the Hammer tcase OD mod on my TF2 because I was thinking it would be too much OD and the way it works, I'd need to gear down more. I'm already at 11T pinion and spur has no room to go bigger. Great job!

[OSRC]

Thank you good sir!

I know the OD mod is very popular - maybe it works better with a longer WB? I haven't given up on it, but I think I'll have to make my own for it to work.

[OSRC]

Finally got my CFX sorted out the way I want it, so as soon as the weather cooperates, it's time for a comparison! Is the "CFX Killer" going to live up to it's name?

First, some comparison shots and info. Forgive the crappy pics, my cell phone (Samsung J7) has a straight up terrible camera! And it apparently doesn't like humidity since it wouldn't focus worth a damn.

I painted up my CFX with the same body and WB, though it's running 1.55's ilo 1.9's.


The CK has a wider track, and sits a bit higher. The stance didn't look right with the wider axles sitting low, so it's a bit jacked up.


Overall ground clearance is about the same though.


Flex-wise, the CFX wins. Though the CK has 80mm shocks, the 70mm shocks on the MST have a bit more actual travel. Not to mention, they are much smoother. The CK still needs some shock work for sure.


Chassis shots of each. The CK has the motor much, much lower in the chassis, though the battery sits a bit higher. With the wider axles, it's COG is much lower overall.


I'll be throwing my CMX into the mix too. Why not? Maybe even a CC01 since they all use the same size body. Tiny tire trucks are taking over here in my shop lately. As they stand right now:


CFX Killer: 2564g, 49.3% on the front axle. Tamiya X-Axto motor, Xcar 45a ESC, Tactic TSX45 servo
CFX: 2406g, 55.3% on the front axle. 35t motor, WP1080 ESC, Tactic TSX45 servo
CMX: 2389g, 53.5% on the front axle. 35t motor, Xcar 45a ESC, 645MG servo.

THe CK has a rear weight bias - that's no good. I'll be giving it a test run first and I'm pretty sure that the Tamiya mini motor will get swapped out to a standard size 35t - that should bring it at least even balance-wise.

Ready to play - if the rain ever stops!

[Natedog]

Great comparison, I agree test it first and get it dialed in better, fullsize 540 motor would help bias and power. Maybe move the lipo cross the frame rails just ahead of the ESC and transfer case.

[OSRC]

Way ahead of you Natedog! Got a bit done over the past few days.

First thing to tackle was the shocks. They were completely hydrolocking with oil, and sticky to boot. Pulled them apart and found the holes in the pistons were blocked by the e-clips. Yup, that'll do it. Used the dremel to semi-scientifically notch the pistons so oil can flow no matter where the e-clip is. Also swapped out the old, swollen O-rings with some Tamiya red rings. Not great, but they actually function now.


Battery moved up to sit on top of the t-case longitudinally. With the motor swap, brings me to a 55/45 weight balance - much better.



Have a bit of clearance issue at full comrpression up front where the driveshaft hits the trans mount. Switched from a WB to a GDS driveshaft as it was a bit thinner. Still hits, but just barely. I'll keep an eye on it.


Swapped in a 35t motor/WP1080 ESC as well. Mini motor probably would have been fine as geared down as it is, but I could use it somewhere else anyway. These Gool/Hackmoto/whatever $10 motors are pretty nice for the price. Especially compared to some other throwaway motors at the price.


Did some testing. Tires are just awful...I remember them being OK out on a trail run, but on rocks and plywood, they were just terrible. Well, they did make cool whooshing sounds as they slid/spun, I guess that counts for something. I forgot to vent them, might have something to do with it - very bouncy.


I figured the gearing for a 1:1 t-case, and later decided on the RC4WD case which has more reduction in it. So the truck absolutely crawls. doesn't even do walking speed. Couldn't get up the 50d ramp - first truck to fail to do it.


*Sigh* 1 step forward, 2 back. Back to the workshop for some changes.

[OSRC]

Back in the shop to make some changes...

First off, even though the shocks were better, they still sucked. Period. Fronts came out better than the rears for some reason...still sticking a bit, and very stiff. Since the rear were the worst, I started experimenting. I found that Axial shocks limited by 10mm with MST springs from my CFX worked out very well. A bit more travel and far, far smoother. Just had to change out the mounts on the bottom.

Before:


After:


All done. I actually have suspension action again! I'm out of shocks ATM, but the front will be getting the same treatment.


Though the double GRU might seem like an odd transmission, it works out very well. 3 screws to remove the trans, 3 screws in the HPI GRU, and 2 in the RC4WD and the entire "transmission" is out and open in less than a minute. Replaced the 4:1 with a 2:1 hoping to get some wheelspeed back. Took all of 5 minutes.


Back to testing.. Can't emphasise enough how nice it is to have a place to test right outside.


Wheelspeed was better, but still a bit slow. Thinking a 1:1 t-case might have to go on. I think it'll be too fast if I remove the RC4WD GRU, but I might try it anyway before coming up with a new t-case setup.

I did swap on some 4.19 Hyraxes and traction was much, much improved. I think they look a bit big, not sure if I'm leaving them on or not.


Still failed the ramp. Mostly, made it once just by a fluke. Just doesn't have any wheelspeed.


So - much better...still some work to do on the driveline and front shocks before calling this one good.

[Natedog]

Are the GDS metal driveshafts female half splined all the way through? Agree that the Hyrax look a little too big on there, but I'm sure the performance is 10X better.

[OSRC]

I'm not sure, but I'll check next time I have it apart.

[OSRC]

Finally got the driveline sorted out. I was looking at different GRU's and T-cases to get the FDR right... it was a bit undergeared previously. Great for torque, but wasn't quite at walking pace - not going to work on a trail run.

I ripped the Revolver out of my Wraith a while ago and it was sitting on the bench...low RPM's, gobs of torque...hmmm. Bolted it right to the HPI GRU with no other reduction and it's absolutely perfect. Great torque and just enough wheelspeed to get down the trails. Not to mention the smaller size works out perfect. I'll have to keep this setup in mind for future rigs.




And thanks to all the of the room I had availble, finally got the winch wired up. RC4WD controller stuck to the side of the servo.


I started adding lights to the truck as well. I'm not big on lights per-se, but so far it's looking decent. Does need an interior or something, the body has a lot of windows and it's mighty airy in there.

[OSRC]

Last time I was out wheeling, I made the remark "I'm totally done with lights"

1 week later, I was adding them to my truck. I had a Tamiya light kit sitting around, so why not. Though I was more focused on performance with this truck, I went ahead and added a roof rack too. Think it all came together pretty nice.



Added some lightweight "cargo" up top and tinted the windows out back a bit. It's a sad substitute for an interior, but it'll work for now.

[OSRC]

Finally got the little TLT truck out out for some proper wheeling. Funny, of the 10 or so guys left after our main trail session, not one of them ever even heard of a TLT. After driving the TRX4 for 4 hours, switching to this truck was a rude awakening.. Steering is not the best, ground clearance is much lower, and the tires are just awful. Nevertheless, got the feel for it after a while and had a good time crawling around.

NO MOTOR VEHICLES!


Wet, mossy rocks and 10 year old Outcroppers just don't mix.



Did get up some pretty serious inclines though...mostly with wheelspeed and some luck.


Very happy with it though. Went fine down the trail, which is what I was hoping for. Even though the tires were not the best, the weight balance and overall handling of the truck were very good. And it came back in 1 piece after 90 minutes of pretty serious trail time. I'd call that a win.

[kincer]

I remember TLT axles, did a build with them once, they worked ok, not my top choice but they worked. That rig is sweet looking though I really like it!

[meatmonkey]

Whatever happened to this cool old school build?

The stacking of reduction boxes is genius, yet the revolver is even better you say? Would you say the revolver will creep as good as a brushed motor running twice the reduction ratio?

I still have a functional tlt axled rig. Built it from mostly spare parts for my kiddo to run. Just wish it turned tighter. Any chance some place still has MIPs for it that you'd know of?

[OSRC]

Still have it, it's doing a great job of keep my self from flying up and hitting the ceiling.

Revolver is a good match as this truck has somewhat tall gearing, and was way too fast/low torque with a 35t motor. An outrunner by nature does not rev nearly as high, but produces much more torque so it's a pretty decent match for the tall gearing. Newer Revolvers creep along amazing at low RPM, no special gearing needed.

No, no idea - pretty sure TLT MIP's are long lost unicorns at this point.