95PGTTech 1/10 2WD ECX Ruckus build

[95PGTTech]

I threw another hex on there that I had that I thought would work, but before we had a chance to go test again the MIP replacement arrived. They might be expensive axles, but being able to order service parts for them is pretty cool. Same experience I had with the GTR shocks.





We got a chance to go out and test today.

I was initially so excited, because between 3 and 4 seconds into the pull I was able to get to full throttle (finally) and hold it...and less than a second later I realized it wasn't accelerating anymore, and as it passed me > 40mph it had a bad smell of burnt clutch (as I so eloquently narrated, I really need to stop talking).

Got it home, and you can see the abusive heat the spur took. It looks like I put my oxy-ace torch to it. The nut wasn't loose at all, the slipper was still set as I left it (full tight minus 1/12 turn). I'm just going to put an eliminator in it at this point. I really didn't want to do that, especially with a locker diff, but there isn't much choice. It'll also open up a few more options for tooth count on the spur gear.

 

[95PGTTech]

Can't have any more clutch problems if there isn't a clutch. Revo 3.3 slipper eliminator, hardened steel 32T mod1 spur.





Had to keep the spring for now just to take up space the threads on the stud don't go far enough down to just run the bearing and spacer. Whatever, seems to spin fine. Left the motors where they were to give you and idea of how much smaller this is than a 38T spur.





Comparo shot between (left to right) stock size 87T hardened 48p, 43T mod1, 38T mod1, 32T mod1. We aren't in Kansas anymore.





All done. Setting backlash on 2 motors is fun, especially when you can't tighten the screws without removing the pinion gear (because it's so damn big lol).





Had a bit of nice weather after picking him up from school so went and ran it in the park. We still need a bigger space and some front suspension work, but it was a great day. More on that later once I get confirmation.

 

[95PGTTech]

I didn't say anything at the time, because I was waiting to hear back from the RC Off-Road Speed Club, but on 10-22-22 James and his Ruckus became the fastest known 2WD off-road RC on the planet. We submitted a GPS and video verification and they approved our submission earlier this week. Today, we were able to back up the run. Overall in the small class (1/8 and 1/10 scale), he is 18th. The 2WD title was previously between two Slash going 47.5mph and 48mph (slight downhill, so a big argument ensued). As a reference point, the small class leader is 94mph on ice and the overall leader is 103mph on dirt (in a 1/5 scale).





We had no intention of competing at this level, this was just a way for us to spend time together and our two dogs (RIP Dolce and Gucci). At 4 years 3 months, James really doesn't care that much about the list. He likes working on it in his "workshop" and the other people he meets at the park when they see this 14lb missile absolutely tearing across the open fields (and sometimes crashing in spectacular fashion). We got a lot of help from members here, on the ECX Facebook group, and the Off-Road Speed Club.





It was pretty consistent all day, we actually got about 12 pulls in. Most aborted due to having to get out of the throttle for terrain. Even an "open field" is extremely bumpy when you walk it. Our 50 was actually on a pretty significant incline, it's almost like the added load helped plant it better. The front end is still very "pogo stick," so I ordered 1.8x24x30 springs for the front to try and stiffen it further. We have a few more things we want to try, I think there may be a 60mph in this on a "perfect" run. After about 3 hard pulls back to back we hit thermal cutoff, so we are finding the limit of what these motors can be geared.

 

[WithinU]

that's awesome! Nice job James!

 

[95PGTTech]

that's awesome! Nice job James!

He says thanks!

We have been back out at it testing, I really cranked down the front shocks until the new springs get here and installed limiting straps (like you see on big HP roll race motorcycles) and it really didn't seem to change anything. If anything, the front end is lifting from power, not from terrain.






We switched to trying to add weight, using some of my impact sockets as test weights. It was driving really funny, pulling left hard, to the point where I'm trying to adjust the trim to compensate. I figured it was the sockets up front probably moving around and not being centered. Brought it back in and looked everything over, figured maybe we were bottoming out the front suspension so I took off the limiter straps. No change, and seems to be much worse at speed. It wasn't making the mph it should either. We stopped multiple times and couldn't figure out what was up. Eventually, it stopped going altogether except in about a 10ft circle. The problem became evident.







Snapped the left rear output shaft off of the diff at the pin. That explains a lot of the behavior. We noticed something else too.





The right rear is missing its banding. Best guess, the right rear lost its banding, ballooned, which makes it significantly larger diameter than the left rear and it strains the output gear (since it's a locker it can't spin both tires at different rates, though this problem would have superheated a diff and killed it too). Upon disassembly, most of the rest of the transmission looks really good. The other side of the diff that survived has had its axle pin hole really boogered up, it wasn't long for this world either. The problems of big power and a slipper eliminator...





Not pictured we also managed to shear the 1.5mm input shaft pin which was the part we feared most would fail. Supershafty said go back to the pin that they sent, not the high speed drill bit blanks. We will see. I'm going to add loctite 638, my local machine shop uses it to bond gears to shafts with a holding pressure of 4500lbs. Hopefully this assists the pin some. This wasn't some stock output, that was a one piece hardened Robinson Racing 1544. To help prevent that from failing again, Supershafty is sending us out an Incision hardened gear set and their 8mm "bombproof" outputs with hubs for our MIP x-duty driveshafts.

I re-banded both tires. I figured while I was sitting there doing the one, there is just as much time/miles on the other one mind as well do it too.




Things on the to do list for testing (if we can ever get this reliable enough for back to back consistent passes)

• stiffer front springs
• more/less front ballast
• body on/off
• wing on/off
• better (bigger/flatter) location

 

[95PGTTech]

Gearset and outputs are here. Pics speak for themselves...






This is what the shop calls "studlock". I doubt I even need the pin at this point. The stuff smells like vinegar and says use gloves. Supposedly it comes apart with 450F heat. I hope to never have to try. Short of welding the gear to the shaft (which comes with its own issues), I can't think of a better bond.





Look at the 8mm output vs the 5mm transmission and motor shafts...





While waiting on the new springs to arrive (somewhere on a boat from China), I put in the Felony front springs (35mm 27 lbf/in ARA330632). I zip tied my ballast socket better to the shock tower instead of the front bumper to try and stop it from moving around. I think the right spring is somewhere in between, these springs could probably use more ballast. I'll bring it along to the park next time we run.





I was out of glue anyway, so I got this fancy stuff with a UV light activator to glue the new bands on. After one test run, it held up well. Per recommendation from SuperShafty, I went away from the MIP set screws and went to a Revo 4x15 set screw for the axles. I'm not sure how I feel about it, not being threaded at both ends.





Had a chance to get it out today, mixed bag. Didn't break anything with the trans. New belts on the tires worked well. Big winds, rolled it once, ejecting the ballast and destroying the front body mount in the process. Ordered up another. I had intended on adding a second and third ballast but never got to it. Tried to run it again with no ballast, and, not surprisingly, rolled it again. Ejected the upper battery and destroyed the front right tie rod. Discovered I need to crank the steering saver down much tighter too. Ran a bunch of upper 40s, but still couldn't really get into it due to terrain, wheelies, wind, etc. We really need to find a bigger and more consistent environment we are really chasing our tails here. It does seem to be going the correct direction with more ballast and more front spring, but still really hard to tell being this inconsistent.

 

[95PGTTech]

Ordered the body mount, I had a replacement rod on hand (correction, it was the caster rod, not the tie rod). Set the alignment again, did a better job securing the ballast (743g for the two sockets, by the way, bringing the total weight of the RC to 14.2lbs or 6440g) - it was 5.5lbs stock. Also for reference, this truck did 23mph stock as tested by RC magazine companies...on pavement. Tightened up the steering servo saver considerably trying to eliminate a speed wobble).





Made a simple better battery holder, no more zip ties. Painted the GPS an obnoxious yellow I had, a project that has been on my mind for awhile. A long time ago we ejected the entire front bumper assembly and the GPS in a big hit and didn't recover it for a few days because it was black and hard to find. By then moisture had killed it. The battery ejection issue reminded me to finally get this done.




Went out and ran it this morning, it was steering in a very odd manner again. I made some adjustments on the radio and it seemed like everything I did made it worse in one way or another, so looked everything over. Somehow lost the left rear bottom shock bolt and washer. Threads are still in the LCA, it just backed out I guess.






Came back out later after I picked him up from school and it was going straight and making some solid passes - towards the end, he was actually able to get full throttle - making me believe the theory that if we can get a bigger and better environment we can remove some of this front ballast and get a long, fast pull. New personal best for the truck 52mph. Not an official speed, because he clipped a tree while in the braking zone and crashed it, which disqualifies the speed. Still, it's fun to know there is more in this. Motors were still barely warm after 3 hard back to back pulls.

Crash had minimal (but ironic) damage, ripping the threads out of the rear right LCA shock mount and some superficial scratches. I ended up just through bolting both sides to prevent this from happening again. I did a quick once-through and everything looks pretty good, reset the pinion mesh(es), adjusted the rear spring preload, and went back down to one socket on the front end. I had a problem with the battery charge leads on the B6 knockoff charger I have showing a disconnect error the positive cable was coming loose in the Deans connector (and then needed a deans - xt90 adapter) so I got a new xt90 lead set and found these 4s extension cables while I was at it...a lot less pain in the butt now.

 

[95PGTTech]

Not a great day. No excuses, it was nice out, I still haven't found a better place to run. Dropped my kid off at school and had a free half hour window so had the idea of trying back to back passes with and without the wing. Never got there, clipped a soccer goal (the same one actually he did a different time on a video here) with the right front and rear and absolutely tore the truck up. GPS said 47mph.

In the front, it seems I just tore out the lower shock mount from the control arm. I'll through-bolt them like I did the rear. I'm probably also going to put spherical bearings in the upper and lowers. I haven't torn it completely down yet, but that seems to be the extent of the damage up there.





In the back, the through-bolting actually held up! The control arm didn't, and tore through the control arm pivot pin. It caused what is probably just superficial damage to the rear bulkhead, but I have another on hand anyway and I needed to get this completely torn down to look for other things so I'll replace it while I'm in there. The pin seems fine, the arms are RPM so I reordered a set.





The other obvious failure is the MIP driveshaft hub. I can't complain, when the pin/arm got bent like that it deflected the driveshaft into an angle it absolutely should never have been in. I'm glad something more expensive didn't break, the hub is a $10 part.





Had to take the rear ESC and batteries out to get to all that and found one of the brass standoffs snapped off in the chassis. That should be fun to drill out (m3). If you look closely in the same pic, you'll see where the tapered head bolt that goes down to the rear mount pulled through the chassis. It actually broke the tab off underneath too. I could probably try a large fender washer and a button head bolt but I'm really getting into where the battery needs to be. I think I'm putting another chassis in this.




Rear shock tower to rear bulkhead bolts...ouch. Upper shock bolt took a decent bend, may have even bent the tower just a tad at the ear





Both batteries took a pretty decent beating to the outer clear plastic covers so I replaced it with packing tape. Got most of the parts ordered, going to tear apart the front end tomorrow and clean everything up. If you haven't yet learned from my thread, the faster you want to go, the more expensive it gets (exponentially). When its going well and when it's not.

 

[95PGTTech]

Got everything else tore back down and cleaned it all really good, just giving this thing an entire nuts and bolts go through, it needs it. Almost immediately I was glad I did, found a split in the axle tube (the one that had the broken hub) that was covered by dirt/grease. Also bent the pin. MIP sells service parts for both. Clean parts are just more enjoyable to work on anyway.





I definetely tweaked that ear of the rear shock tower. I was able to bend it back into place and rethread the hole.





Figured out why the front lights don't work anymore - when the socket decided to leave I think it took the wiring with it. These were actually really helpful, when the RC is really far away in the distance on these big long runs having a light bar like that makes it much easier to discertain its speed and direction and get it going.





Another ouch I found only because of a thorough cleaning and go-through





New body posts arrived, I may spring for the fancy shiny blue ones but these will do for now. I also through-bolted the front lower shock mount in the way I previously did the rear one (which actually held up to this hit, despite the LCA and the rear bulkhead being torn up).





I was going to not open up the trans because it spun freely and showed no signs of problems, but I noticed on the diff outdrives the cross pin is slightly off side to side. I couldn't remember if it was like that when I installed it, and I was fearing it may have broken the bolts off and rotated. I was wrong, all is well, that's just how it is. I also checked that little 1.5mm pin on the input shaft and, so far, that high speed steel and the stud lock seem to be doing their job.




Waiting on LCA and chassis to arrive at this point to move forward. At this point, considering going back to a larger single motor. I have a max8 combo sitting around anyway. The dual motor was really just an experiment with stuff I had sitting around anyway. I think it has proven to be not worth the weight for what we are doing in this application, I'll stew on it a little.

 

[95PGTTech]

Changed up the front nose plate a little, mostly just adding material to enclose it even tighter. I did find a bit of road debris in there, which is annoying to dig out of the tungsten putty. Generally just cleaned up the lines and made it fit a bit nicer.





New rear LCAs arrived. I always wondered looking at the back of the truck if they were twisted, but figured being plastic they couldn't be. Obviously, I was wrong. Drilled and tapped the new ones for M4 knuckle pins and through bolted for the lower shocks just like I did previously in this thread.







Aluminum/carbon replacement body posts. I'm hoping the plastic ECX pieces they bolt to will still be the failure point.

 

[95PGTTech]

Been kicking around the idea of going back to a single big motor. Not using the stock transmission and stock motor plate, I am no longer limited to a 36mm can. I have a first gen (non-sensored) max8/4274 combo sitting around. I believe it's 2250kv. I was able to install it in the lower motor position and put the bottom bolt in. I really didn't want to have to move and re-slot the plate, but I was able to find enough meat in one area to drill a m4 hole. Not optimal, as I won't have any mesh adjustment whatsoever, so I need to find gearing that fits a good mesh as-is. Luckily, 1.0mod is pretty forgiving. This will allow me to experiment without doing anything super permanent that I can't put right back if I don't like it. I ordered a 42T spur, and I have a ton of pinions on hand.





The reason is simple - dual motors were cool, but were just an experiment, and I think they may not be worth the weight for what we are trying to do. We've only gone 2mph faster than an identical single motor setup (3674, 4S, max10sct). I could be wrong - the cause could be elsewhere - suspension, aero, terrain choice. But I have this on hand and it's an easy enough trial and error at this point. The dual motor setup is great at making torque - acceleration out of the hole - which makes turning big gear ratios from a low speed on non-sensored motors much easier, but in every other respect is exactly the opposite of what we want - a low-torque, linear powerband that makes big power up top.

Here are some side by side weight comparisons, the most notable being the combined weight of ESC, motor, batteries being almost a 600g difference (on a 6400g dual motor RC)





In theory, I could run the single motor on 4S, which would drop about another 300g, but realistically the system is rated at 6S, we are going to put the screws to it. The two 3S I have on hand aren't matching, that's why I did the side by side of them, so there's 70g saved there by going to the two Yowoo. That's a pretty serious weight difference, especially where the weight is located.

So, I guess we will give it a shot. Still waiting on the new chassis to start putting it all back together, and still on the hunt for a better spot. I did find a large, nice astroturf field where he plays soccer, but I'd need to ask permission to run it there for sure, and I'm not sure how I feel about that. If I just didn't give a damn, we live across from a golf course and the hole is a long par 5 we could just send it down the middle of the fairway one day but I'm not sure they'd appreciate the Badlands tearing up their carefully cultivated surface, and I don't need that kind of drama in my life (nor is it teaching James to do things the right way). For now, took apart the 4674, everything looks good, cleaned and lubed it. Flashed the ESC back to stock and set its endpoints with the radio.