Brian's Redcat Sumo Micro "Low Dollar Crawler..."

[89redranger]

Well, yesterday I went by a local RC race shop/track/hobbyshop to finally check one of these little guys out. After about 20 minutes of chatting with the owner he asked me what other micros I had and got to talking about my facebook group for micros. I gave him a brief rundown of the page and the fact that I started it just to boost local interest in the micros, told him about the projects I had, and then remembered my tricked out drift Losi Rally Car was still in the car from a prior day's runs.

Long story short, he traded my well used Micro Rally and $20 for a Sumo, brand new and still taped shut. It wasn't out of the box 20 minutes before I let the mods fly. As a matter of fact, this is ANOTHER rig I never drove STOCK...

With this rig I intend to use as many stock or recyled parts as possible, and not spend a nickle more than I must. Earning it the title, "Low Dollar Crawler."

Anywho, here are a few pics and explanations of last night's little mod session. There will be more coming with this project.

I really should have gotten pics of this little guy out of the box. My oh my, the changes. I robbed the weighted Claws and wheels off my Trekker, mounted them on stock Trekker hexes for a free widener.


Mounted up an MG90s in the front, eliminated the rear steer, ditched the AAs and battery boxes for a LiPo, moved a lot of the wiring and board around to get them down low. She's stable now...










Put the stock Redcat wheels and tires on my Trekker. I think they'll work better as an all around tire. They're wide and will give good flotation in the soft stuff.


The Trekker and RSMC side by side. I've stretched the wheelbase on both to 5 1/8" for climbs.


My custom rear lockouts and battery holder. I'm debating running it in the chassis though.


Proposed permanent battery location.With the battery here it looks and handles almost identical to my 1.9 MRC Pro. You can also see the longer 2-56 lower links I've made (they still need tube over them), and how I've moved the original lowers up to replace the stubby stock uppers. The stock setup was very rigid, bound badly, and had massive axle steer, caster change, and wheel hop. This setup is VERY plush and stable. It just floats up things. As I said, it drives like my 1.9 comp rig. Just needs more power.


New location of ESC/RX board. Note shrink tube to cover the servo output on the board where the original rear servo was plugged in. Don't need a shorted out board!


Here you can see the original lower links moved into the upper position. I may play with the geometry a little, but it's super close to perfect. It climbs like a spider when it doesn't stall. Even on 2s it's gutless. Looking into running a bigger motor into the original gear head. More low budget tricks coming!

[89redranger]

Second round of mods done! Just got through mounting up the motor from one of 645MGs to the original gearhead and cutting 3 coils off each spring. This motor still runs warm (was built for 4.8-6V) but not near as hot as the stock motor. I also noticed that the board runs MUCH cooler than with the stock motor. So far I'm VERY happy with this mod. Gobs of torque, smoother delivery, and a little more weight up front.

Cutting the coils helped a ton as well. Softened it right up, but not floppy like with a droop setup. As it turns out, the original springs were longer than the shocks anyway. Cutting 3 coils off each spring matched the spring length to the shock body. No more preload!

Pictures soon...

[89redranger]

Second round of mods today...

Adapted the motor from a Hitec 645MG where the original once went. It was a little bit of a chore to fit in the rig, but well worth the effort. Look closely and you can see the nuts I had to use to space the motor off the gearbox. I had to do this as the original motor had a smaller diameter snout. Slower speeds, smoother power delivery, monster amounts of torque, and longer run times were had with this one simple mod.


Here you can see how I soldered on a factory Redcat plug so it still plugs in. The clearance is tight between the servo and motor. This wouldn't work on a stock wheelbase rig.


Here you can see the that the weight of the new motor actually pulls the front end down. Between cut coils and the motor the rig is very plush. The forward bias is awesome over a Losi too. It climbs right up things that leave a Losi teetering.


Notice in this pic how I cut down the posts on top of the trans and lowered the electronics tray. When cutting I left enough room to run the servo and motor wire between them, right down the center. Believe it or not, the COG of this rig feels MUCH better than any other micro I've driven.

[89redranger]

Does anybody know how I can get rid of the forward/backward slop that this rig has while driving? None of this slop is from the transmission, it's ALL in the axles. Does the bearing set help that, or have you guys learned to live with it? Out of all things, that is the one deal-breaker for me. I can't stand sloppy trucks that roll when you count on them to sit on a ledge...

Also, anybody have a definite part number or source of bearings for these little guys, or do I have to piece one together? Seems that I got lucky (apparently bushings are spec'd for the trans as well as axles) and landed a rig that had bearings in the trans already, but the damn things are wide open. No dust shields, much less seals...

EDIT: Just ran a pack with my neighbor on his indoor rock pile. I'm pushing around an hour run time on this Hitec motor on 2s. Love it, but my Stroker is soooooo much better still. This setup is slower than my 80T 180 by quite a bit, and still short on power when in really tight spots.

[Slambaam]

Originally Posted by 89redranger

Does anybody know how I can get rid of the forward/backward slop that this rig has while driving? None of this slop is from the transmission, it's ALL in the axles. Does the bearing set help that, or have you guys learned to live with it? Out of all things, that is the one deal-breaker for me. I can't stand sloppy trucks that roll when you count on them to sit on a ledge...

Also, anybody have a definite part number or source of bearings for these little guys, or do I have to piece one together? Seems that I got lucky (apparently bushings are spec'd for the trans as well as axles) and landed a rig that had bearings in the trans already, but the damn things are wide open. No dust shields, much less seals...

EDIT: Just ran a pack with my neighbor on his indoor rock pile. I'm pushing around an hour run time on this Hitec motor on 2s. Love it, but my Stroker is soooooo much better still. This setup is slower than my 80T 180 by quite a bit, and still short on power when in really tight spots.

try some heavy grease in the axles.

[89redranger]

I'm willing to give it a try, but it feels like the pinion in the axle needs shimmed in a little to tighten up the mesh. It also feels like the axle shafts have a pretty loose fit in the spool. How is grease going to fix that (really not trying to be argumentative, just don't understand)? I may play around with loctite in the diff spool to tighten up the shafts' fit a bit, but that's about all I can think of...

[mgb]

I'm liking the looks of the redcat tires on the trekker, nice job so far!

[89redranger]

Finally got around to the 3rd round with this rig. This time around I rotated the front pinion up, flipped the c hubs side to side (allowing me to run the lower shock mount further forward, laying the shocks down for more travel and softening the spring rate) rocked them back for caster, drilled new holes, and built new steering linkage. Also got the truck squared up by measuring and adjusting links, and trimmed up the stock body. Oh, I also put bearings on the diffs. Still need a set for the Cs and pinion, but it's four down...

Let me know if you guys have questions.

























It's really nice to be able to run caster without the front driveshaft pointing at the ground. The combination of the caster, better driveshaft clearance, and laying the shocks out has made a night and day difference.

[89redranger]

Anybody have a coreless motor from a newer servo laying around that they wanna donate? I've been watching youtube videos, and found GamyRC's channel. He has had REALLY good success with the coreless motors on the stock gearbox, but doesn't give a whole lot of details as to how to mount it up. The problem is, on top of being too big, like the servo motor I'm running now, they don't have mounting holes. I'm thinking I'll solder some brass M2 nuts right onto the motor can to hold the motor to the gearbox. BTW, with the Hitec servo motor I have now I ran a Zippy 350 2s for an hour and 24 minutes today. It's just so damn slow and it gets pretty warm (not at as hot as the stocker though).

[Gamyrc]

Hey bro, just wondering if you had a chance to check out my video 22 in it I show all the bearings you need and a shim idea I had a while back to either decrease dramatically the slop in the driveline or to loosen it up for high speed low drag application.
Heres a link so you don't have to look around, hope it helps you out.

22 Redcat Racing 1/24 Sumo Crawler Micro RC with mods / upgrades Ball Bearing 22 - YouTube

[89redranger]

Originally Posted by Gamyrc

Hey bro, just wondering if you had a chance to check out my video 22 in it I show all the bearings you need and a shim idea I had a while back to either decrease dramatically the slop in the driveline or to loosen it up for high speed low drag application.
Heres a link so you don't have to look around, hope it helps you out.

22 Redcat Racing 1/24 Sumo Crawler Micro RC with mods / upgrades Ball Bearing 22 - YouTube

I actually did see that video, and thanks for the input. I actually don't think there's much room to shim this little guy. The looseness I'm getting is actually from the fact that the ring gear fits loosely on the center spool, and the pinion fits loosely on the pinion shaft. I'm honestly thinking either a dab of loctite or glue on both before reassembly will eliminate the slop. I just know I don't care for it. This rig has actually been shelved till I can get bearings and fix this problem. Like I said, of all problems, this one about drives me insane...

[89redranger]

Finally got a little more time with this rig last night and got to do another mod that is free and made a huge difference. Originally, the steering would bounce at full lock because the dog bone pin hits the bottom it's slot in the outer cup. Since I've got the rig I've wandered what could fix it, and just dialed back my end points to keep the servo from throwing that far. I knew there had to be a fix...

Upon searching "Redcat Sumo Micro Crawler Steering Angle," I was once again greeted with one of gamyrc's youtube videos at the top of the search. Basically, his video goes over the process of filing out the bottom of the dog bone cup deep enough that the steering will actually pull full lock through the axle's entire rotation. Damn, this guy's done it all!

Long story short, I sat down with my jeweler's file set and let fly on what was a brand new set of axles. Gamy used a fairly large file set, and got the results he was after. I just knew that I didn't want to take any more material away than necessary. This really is a tedious procedure, but can be done in about 20 minutes/corner. I'm a little more on the anal retentive side and seek the finest results from mediocre tools. Mine took about 45 minutes to an hour/corner! Just remember, this is one of those mods that it really pays to take your sweet time and do it right, you're chopping away at your axles...

53 Redcat Racing 1/24 Sumo Crawler Micro RC with mods / upgrades Steering Fix - YouTube

[DANALLY]

That's some sweet info! I have been watching Gamy's video's and info posts. He really has done it all with those.

I just got my Sumo torn apart and will be mating the axles to my new project soon. Glad you posted this so I can do the mod first!

[89redranger]

Originally Posted by DANALLY

That's some sweet info! I have been watching Gamy's video's and info posts. He really has done it all with those.

I just got my Sumo torn apart and will be mating the axles to my new project soon. Glad you posted this so I can do the mod first!

If you're shooting for something with some wheel speed you really ought to roll the knuckles back for some caster. With the knuckles rolled back you can have caster and get that front pinion up out of the rocks. It's literally as simple as shaving off the 2 nubs that keep the c hubs from turning, turning them back, drilling new screw holes, and building some steering to fit. Not only does the rig turn MUCH better, it actually FORCES the tires into rocks without rolling the tread over. The caster mod is probably still the single best mod I've done yet, and I can't wait to see the results on a faster rig. As you can see, 90% of the parts needed to make the steering work in this new manner are on the rig. They just need modded and you need some 2-56 fully threaded rod to build a drag-link.

Today I ought to have updated pics of the steering and covered links. My camera will not focus on the small dog bones, or I'd get some pics for you guys.

[89redranger]

For what it's worth, I just got an email back from Redcat saying they were going to replace my ESC/RX after I discovered that the antenna wasn't even soldered to the board. The guy tried to tell me that all trucks in their warehouse were the same way in the first emails, and I asked him "shouldn't they ALL be fixed then, does that sound right to you???" The next email was from another fellow in the warranty department that was happy to replace my parts. Apparently the first guy didn't like my questions and the second was quick to shut me up...

First lesson when dealing with warranty people- Know your stuff before you contact them or they'll do their best to weasel out of it.

We'll see what the mail brings me. A proper ESC/RX that stays bound, or another un-soldered pile? Good news is, even if I have 2 crap boards, they look easy enough to fix.