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.

 

[95PGTTech]

Haven't posted in a bit, been too busy wrenching, modifying, running, breaking, tearing apart, researching, repeat. Welcome to racing, and the faster you go, the worse it gets and the lighter your wallet (exponentially, not linearly).

While waiting on everything else my phone got "suggested" an ad for these since I just bought a set of stock ones. In my mind I said they may come in useful to mount a more aerodynamic body since they are a modular mount, but really I just saw carbon fiber and shiny and clicked buy. I unbagged them and promptly took the cutoff wheel to one - nothing is sacred around here.





19T/42T was the combo I came up with that achieves the perfect mesh (I cannot move the motor as it is right now). Certainly not ideal gearing, but should give us some idea of whether we are going the right direction going back to a single big motor.





Repair parts start trickling in. Supershafty is really great to work with.




For the 8mm outputs, you can run either the stubby MIP set screws from each side, or the traxxas 15mm from one side, but I didn't like how it left the pin through the threaded opposite end with some slop, especially in a big power application like this. I ended up ordering new style MIP set screws in 13mm length, then grinding them shorter. Old stubby set screw on one side (it's on the tip of the allen wrench), modified MIP long set screw on the other side, they meet nicely in the middle.





Aluminum shock caps with bleeders, locking aluminum lower spring perches and rod ends. This should put an end to the issues. If they continue to function nicely, I'll order the front set to match.





And it's here, the third chassis this thing has been on since we've owned it

 

[95PGTTech]

Lets get this party started





One of the things on my details to do list was through-bolt the entire rear shock tower, but it requires a ton of disassembly to get to this point. Good time to do it. Super big pain in the ass to assemble and disassemble, but should be a lot better than screws into plastic.





The 3S is hilariously lower. Rear done




Front assembly going on




Another area I modified the old chassis in and copied to this one was to cut the fins out of this area, allows the batteries to get a lot farther forward and lower.





Ballast. This was what was in the old nose, and is going back in. I had another 12 or so wheel weights @ 7grams each.




Trying so hard this time I used a razor and goof off to scrape off the double stick tape that comes on the wheel weights. Cuts down on dead space, removing 4 layers of it actually allowed me to get another layer of weights in. Glued. Cut down some in my band saw to get them 2 and a half wide versus just 2.





Tracked it all as best I could, and came up with a total of 633g, so probably 50% more than before. Wish it was farther forward in front of the front axle. I'm still trying to think up a way to modify the front bumper to be able to hold removable brass weights (not my impact sockets zip tied on LOL)

 

[WithinU]

Dang dude......do they have a rehab for this hobby?

 

[95PGTTech]

Dang dude......do they have a rehab for this hobby?

You know you have a problem when other RC guys are pointing it out. My son and I are like this in all our interests, and that's the main reason why we each own one vehicle. It keeps a (relative) cap on the time and money invested. He pretty much got indoctrinated into it, I'm a former drag racer and currently do track days on my motorcycle, mom formerly did autox/road course, dad bracket racer and national champ slot cars, bunch of uncles still run sprint cars (dirt) at a real high level. My brother is probably the only non-racer in the family that I can think of, and he's a robotics engineer and just as competitive as any of the rest of us.

 

[95PGTTech]

Coming together now. 3S 100c 5000mah run in series. In the second pic you can see where I was able to get another row of weights in (21g) by clearancing them a little to clear the plate.





Before I put the covers back on, I took a pic of my custom steering linkage. It deletes that giant offset rod normally on the servo arm. I forget what brand rod arms I used to get them that short but it's back here in the thread somewhere. I bent that rod (or twisted the servo arm) multiple times.





I would venture to say the max8 is the absolute biggest ESC you'll be able to get into this location. It's so tight I clearanced the front shock tower to give room for the front-most motor wire. For now just cobbled together the wiring. This is an ESC I bought used and repaired/replaced a capacitor in and wanted to make sure everything actually works before I went further.





Maiden voyage





In a *SHOCKING* result, we blew it up. It quickly just had a generally bad sound to the drivetrain, but nothing visibly externally wrong like teeth or mesh and I took the pinion off and it wasn't a motor noise. Made a couple half pulls on my property, everything seemed to be working fine, then went over a rough section which got it 4 wheels airborne a few times and then had no forward movement. The pinion spins, the spur spins, not the axles. So out comes the transmission again.





We finally did it, we just straight sheared that 1.5mm pin that holds the input gear to the input shaft. The high speed steel drill blank 1.5mm pin. It wasn't launching it, we were easy on it, and it wasn't just power, we never got to that point, I think it was the issue of the rear catching a little air and then coming back down with a slipper eliminator (similar to why you don't jump one, when you come down the wheels are spinning faster or slower relative to the ground and it just shockloads the drivetrain). I'm going to put the crazy input shaft I Frankensteined out of some others that I made earlier in the thread and try to put the big RR clutch back on and just run it super super tight, because off-road speed racing there are a lot of situations where we hit uneven ground that can't be avoided.





While I'm at it, and now that the batteries easily come out again, I clearanced this area of the rear of the chassis to allow easy removal of these two screws. A lot easier than removing the vertical ones that hold that tiny plastic piece to the front of the motor mount (I would be delusional to think this will be the last time the trans is out).





Sigh...welcome to trying to go fast kid, especially in a relatively new area or a new platform. The weather is starting to get nice though, and it's fun being out there. It's only money and time anyway.

 

[WithinU]

I have to say the truck looks like a beast. I am enjoying reading your posts, even if ones like this post are hard to read.
Would there be any benefit to looking into a more direct drive transmission?

 

[95PGTTech]

Frankenstein input shaft has a 2.5mm pin (I believe I drilled that out, I think it was a 2mm, before I learned my lesson about drilling and bending input shafts), so this basically requires me to go back to the RR gen 3 slipper as it is the only hub I have of any kind that uses that pin (and...I'd like to get a slipper back on it, and this big one was the only slipper I've had that doesn't just get toasted under power). I want to say it was like 17/44 in this setup (I can't move the motor yet, I need to pick a pinion that fits for mesh).





I found this company on etsy that makes these neat on/off switch plates for max8, 6, 5, 4 escs basically on top of the ESC fan, which is pretty cool for me with limited space here (and wanting some of that wiring up and out of the way).





Read to go shake it down - the wiring is bothering me, but whatever.





First problem we found was really erratic behavior (loss of steering, sudden full throttle) beyond 50-ish feet...that'll really make you pucker. This has happened to us before, so we knew where to look. Receiver must have developed a break somewhere in the antenna wire we can't see in a previous crash - swapped in a new receiver to test, problems solved. Other than that, everything seems to work just fine.





Removed the clear heat shrink protection from the new battery and did my clear tape to match, then taped the two of them together so I can ditch the velcro strap and get it to sit in there that much tighter. Put a small clearance in the battery tray section of the chassis to allow the bottom battery wires more room not to get pinched.

 

[95PGTTech]

I have to say the truck looks like a beast. I am enjoying reading your posts, even if ones like this post are hard to read.
Would there be any benefit to looking into a more direct drive transmission?

I would really love to go to something else, like a mod1 transmission, or maybe even a belt drive with the spur directly on the rear axle, but I haven't found anything that really has a legitimate chance of working (without essentially building a new chassis). Something like the DR-10M would be awesome, it moves the shock tower further back so the motor mounts on the front instead of the rear and shifts all the weight forward in the chassis in front of the rear axle.

A side project that I haven't been talking about is exactly that - a custom chassis. The major changes are a 4mm pan style chassis, longitudinally mounted motor (like in a 4wd, where the motor goes front to back), a traditional rear diff/IRS, the batteries mounted up front for weight distrubtion, and 17mm hex (not adapters). Keeping the same wheelbase and track width so we can mount the "stock" Ruckus body. We've made a few different designs in plexiglass, what's really holding us up is figuring out which front end to run - the leader so far is Kyosho Scorpion XL. My brother is 3d printing new battery cases for us custom to the chassis.

 

[WithinU]

We have all seen that you have put a significant amount of time into this truck.
I personaly think it would be cool if and when you get to a point that you think you got it as good as you can get, and it is fairly plug and play.
It would be cool to see a build sheet that others could use.
I mean it may never get to that point, but you never know.