fyrstormer
RCC Addict
(I originally posted this in the Losi MRC forum, but things are pretty slow since the Losi MRC is discontinued, and this isn't really a Losi MRC anyway.)
I liked the way the Slickrock looked since the first time I saw it, but I ended up buying a Wraith instead. That was a good idea, because the Wraith is such a capable vehicle once suitably upgraded, and I never would've been satisfied with the Slickrock if it had been my first crawler. However, with a year of Wraith ownership under my belt, I circled back around to the Slickrock and decided to see if I could make it a worthy crawler.
The first upgrades I did you can see clearly in the picture above: I installed the factory-option stick-on light bar, zip-tying the cord to the frame to keep it safe, I added 2oz of lead weight to the front axle to improve front-wheel traction, and I replaced the stock wheels and tires with Pro-Line Chisel 1.9" tires mounted on Pro-Line FaultLine 1.9" wheels. The Chisels are unfortunately discontinued (I swear there's a UN Special Committee for discontinuing products I like), but I managed to pick up two full sets of tires, so I'll have spares when (if?) these wear out. (after several runs they still look brand-new, which is kind of amazing, I think.) I assume the tire upgrade is a big improvement over the stock tires, but I don't actually know firsthand, because I sold the stock tires as new before I ever ran the vehicle. Based on other people's comments about the traction and the rate-of-wear, I'm confident the Chisels are a solid upgrade. Certainly the foam is much softer, which would help a lot regardless of any other factors.
The second upgrade took a lot longer than just bolting on some new tires -- and I don't say that lightly, because a complete set of FaultLine 1.9" wheels involves tightening 128 tiny little screws -- a good way to pass the time at work while waiting for a database backup to complete. The second upgrade was replacing the awful 3-link suspension with 4-link suspension. (I still don't understand the math that causes 4-link suspension to resist torque-twist, but it works, and that's good enough for me.) First I did the rear suspension, which was much easier, and it was a good opportunity to experiment with the threading and bending tools I'd picked up from the hobby shop.
Finding places to anchor linkages on a frame that doesn't have dozens of little optional-placement holes is never fun, but once I got the ESC off the rear axle and removed the mini-servo plate that the ESC was attached to, I realized I could just use the studs where the mini-servo plate had previously attached. There were originally three studs, one in the front and two in the back, so I cut the front one off and attached the links to the two studs in the back. The rear axle barely rotates when the suspension compresses now, whereas before it rotated away from the frame noticeably. This is definitely a good setup for the rear suspension links.
Building the front upper links was much more frustrating. There's a servo plate in the way, which can't be removed because the servo obviously needs to have a place to sit, and that forces some compromises on the positioning of the front upper links. On the bright side, the links can be attached directly to the back edge of the servo plate, spacing their connection points wider-apart and giving them more ability to resist torque-twist.
I managed to break two of them in the course of figuring out where and how sharply to bend the aluminum rods, and then I broke another one when testing the vehicle, so by the time I was done I'd built 5 front upper links just to have two that worked. (if I break another one when driving, I'm just going to make the next set out of stainless steel, now that I know my hobby shop stocks stainless steel rods in the proper diameter.)
Meanwhile, I had also 180-ed the transmission plate and replaced the stock motor with a Losi Insane 370 motor for extra power. (I may have to get a different motor eventually; I know from past experience that the Insane 370's replaceable brushes handle water spectacularly badly -- but I'll deal with that later.) The spur gear cover is now facing the rear of the vehicle, which freed up a bunch of space to put the battery in the front. It required removing the stock battery box, but that was long-gone anyway, and I was left with a frame full of empty space and no good attachment points for the ESC and receiver. Some people have built replacement plates and stuck the electronics to it using foam tape, but I decided to take a different approach: I cut channels into the outside surface of the frame, ran zip-ties through the channels, and zip-tied the ESC and receiver to the frame so they can't possibly come loose. The ESC was attached to the side of the "passenger compartment" opposite the transmission, and the receiver was attached in the same place as it is on my Wraith -- between the front shocks, a convenient empty space that wasn't being used for anything in the stock setup.
Having removed the stock battery box, I also had to come up with a good way to secure the battery. I had discovered that the 2000mAh 2S LiPo packs that I use with my MERV are *just* the right size to fit in the "passenger compartment" sideways, and after a couple weeks of trying to ignore the problem, I finally sucked it up and spent all night cutting, tweaking, and painting a Lexan plate for the battery to sit on up-front. I also took a spare Velcro battery strap from my Wraith (I only needed one of the two straps that came with the Wraith, because the front of the battery is retained by the vehicle frame), cut it shorter, and sewed it back together in the right configuration to hold a smaller battery. The strap passes through two cutouts in the battery plate and also helps retain some of the electronics wiring as it passes under the battery plate.
While all this was going on, I started to realize that despite my best attempts to make upper suspension links that cleared the other parts effectively, they were still rubbing against the shocks when the axles tilted. I'd already had one of the stock plastic shocks fall apart twice (I *hate* plastic shocks, they're never strong enough!), so I'd ordered a set of the factory-option aluminum shocks and some Mini-T rear springs to go with them. When I started to assemble the aluminum shocks, a solution suddenly hit me: I could space the lower shock mounts further outboard on the axles by bracing the shock mounting points with spare pivot-balls from the original shocks, and then using extra-long screws to secure the shocks out beyond the shock mounting points. This gave just enough extra clearance that the upper links no longer impacted the shocks (especially in the front), and also improved torque-twist a little bit.
There were still more issues to sort-out, though. The stock center driveshafts were plastic slider-type axles, and the sliding parts fit pretty loosely too. That was no good. After some searching and an accidental order of the wrong part, I eventually figured out that eRacingPro makes (or at least sells) steel center driveshafts for the Losi MRC, and they fit on the Slickrock just fine too.
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I also found 3Racing steel CVDs to put on the front axle, to get rid of the uneven wear inherent in the dogbone-style joints the front axles originally used. (the rear axles also use dogbones, but since they don't steer, there was no need to upgrade them -- the rear dogbones are enclosed in the axle housing, greased thoroughly, and will probably never wear out.)
Oh, and I managed to scrape together a set of factory-option steering knuckles, the inner parts intended for the Slickrock and the outer parts intended for the Losi MRC. The anodizing isn't an exact match between the inner and outer parts, but it's close enough that I don't care. The rear axles still have the stock plastic lockouts, but they don't have to do any of the hard work, so that's fine.
There's something I can't show you, because it's buried inside the front axle, but it's really cool that someone figured out this would work: I replaced the front diff pinion with one from a MERV, which has 15 teeth instead of 14, so it gives about a 7% overdrive to the front axle -- not a huge amount, but every little bit helps. I installed the MERV diff pinion with a 1mm-thick spacer behind it to achieve the correct positioning, and the set-screw on the center driveshaft tightened right up against the thru-hole in the back end of the MERV pinion shaft. I instantly noticed an improvement in steering, because the front wheels are able to rotate faster, which is necessary when turning corners. I suppose it also helps a bit with climbing, but frankly just improving the turning radius is a good enough reason for this mod.
At this point I was getting close to finishing the build, but I still had to do something about that stock servo. There wasn't anything *wrong* with it, per se, but stock servos are never very good, and plastic-geared servos on rock crawlers (even small ones) are just failures waiting to happen. Conveniently, Hitec has a new low-profile servo available that fits perfectly, with even more clearance behind it than the stock servo had, *and* Hitec appears to be admitting that the Futaba-style 25-spline design has won the battle -- this servo comes with a 25-spline arm-mount, so I didn't have to figure out how to replace the stock servo horn.
...except I did replace the stock servo horn, anyway. The original one steered fine, but it stuck way out in front of the servo, and often caught on rocks. That was no good. So I replaced it with an OFNA low-profile servo horn, and then while I was at it, I decided to try making new steering linkages as well. The stock plastic steering linkages were also pretty bulky and tended to hang-up on obstacles, so replacing them would improve overall clearance. I knew the aluminum rods I had used to make the upper links wouldn't be strong enough to withstand getting smacked into rocks, so I decided to go with steel instead. Not trusting my bending and threading tools to handle steel rods without breaking, I opted for pre-threaded rods -- and then I carefully ground-off the threads from the exposed parts of the steering linkages, then chucked the linkages into my Dremel so I could smooth them out with emery paper. Let me tell you how much fun THAT was. Yeesh. It came out well, though.
I liked the way the Slickrock looked since the first time I saw it, but I ended up buying a Wraith instead. That was a good idea, because the Wraith is such a capable vehicle once suitably upgraded, and I never would've been satisfied with the Slickrock if it had been my first crawler. However, with a year of Wraith ownership under my belt, I circled back around to the Slickrock and decided to see if I could make it a worthy crawler.
The first upgrades I did you can see clearly in the picture above: I installed the factory-option stick-on light bar, zip-tying the cord to the frame to keep it safe, I added 2oz of lead weight to the front axle to improve front-wheel traction, and I replaced the stock wheels and tires with Pro-Line Chisel 1.9" tires mounted on Pro-Line FaultLine 1.9" wheels. The Chisels are unfortunately discontinued (I swear there's a UN Special Committee for discontinuing products I like), but I managed to pick up two full sets of tires, so I'll have spares when (if?) these wear out. (after several runs they still look brand-new, which is kind of amazing, I think.) I assume the tire upgrade is a big improvement over the stock tires, but I don't actually know firsthand, because I sold the stock tires as new before I ever ran the vehicle. Based on other people's comments about the traction and the rate-of-wear, I'm confident the Chisels are a solid upgrade. Certainly the foam is much softer, which would help a lot regardless of any other factors.
The second upgrade took a lot longer than just bolting on some new tires -- and I don't say that lightly, because a complete set of FaultLine 1.9" wheels involves tightening 128 tiny little screws -- a good way to pass the time at work while waiting for a database backup to complete. The second upgrade was replacing the awful 3-link suspension with 4-link suspension. (I still don't understand the math that causes 4-link suspension to resist torque-twist, but it works, and that's good enough for me.) First I did the rear suspension, which was much easier, and it was a good opportunity to experiment with the threading and bending tools I'd picked up from the hobby shop.
Finding places to anchor linkages on a frame that doesn't have dozens of little optional-placement holes is never fun, but once I got the ESC off the rear axle and removed the mini-servo plate that the ESC was attached to, I realized I could just use the studs where the mini-servo plate had previously attached. There were originally three studs, one in the front and two in the back, so I cut the front one off and attached the links to the two studs in the back. The rear axle barely rotates when the suspension compresses now, whereas before it rotated away from the frame noticeably. This is definitely a good setup for the rear suspension links.
Building the front upper links was much more frustrating. There's a servo plate in the way, which can't be removed because the servo obviously needs to have a place to sit, and that forces some compromises on the positioning of the front upper links. On the bright side, the links can be attached directly to the back edge of the servo plate, spacing their connection points wider-apart and giving them more ability to resist torque-twist.
I managed to break two of them in the course of figuring out where and how sharply to bend the aluminum rods, and then I broke another one when testing the vehicle, so by the time I was done I'd built 5 front upper links just to have two that worked. (if I break another one when driving, I'm just going to make the next set out of stainless steel, now that I know my hobby shop stocks stainless steel rods in the proper diameter.)
Meanwhile, I had also 180-ed the transmission plate and replaced the stock motor with a Losi Insane 370 motor for extra power. (I may have to get a different motor eventually; I know from past experience that the Insane 370's replaceable brushes handle water spectacularly badly -- but I'll deal with that later.) The spur gear cover is now facing the rear of the vehicle, which freed up a bunch of space to put the battery in the front. It required removing the stock battery box, but that was long-gone anyway, and I was left with a frame full of empty space and no good attachment points for the ESC and receiver. Some people have built replacement plates and stuck the electronics to it using foam tape, but I decided to take a different approach: I cut channels into the outside surface of the frame, ran zip-ties through the channels, and zip-tied the ESC and receiver to the frame so they can't possibly come loose. The ESC was attached to the side of the "passenger compartment" opposite the transmission, and the receiver was attached in the same place as it is on my Wraith -- between the front shocks, a convenient empty space that wasn't being used for anything in the stock setup.
Having removed the stock battery box, I also had to come up with a good way to secure the battery. I had discovered that the 2000mAh 2S LiPo packs that I use with my MERV are *just* the right size to fit in the "passenger compartment" sideways, and after a couple weeks of trying to ignore the problem, I finally sucked it up and spent all night cutting, tweaking, and painting a Lexan plate for the battery to sit on up-front. I also took a spare Velcro battery strap from my Wraith (I only needed one of the two straps that came with the Wraith, because the front of the battery is retained by the vehicle frame), cut it shorter, and sewed it back together in the right configuration to hold a smaller battery. The strap passes through two cutouts in the battery plate and also helps retain some of the electronics wiring as it passes under the battery plate.
While all this was going on, I started to realize that despite my best attempts to make upper suspension links that cleared the other parts effectively, they were still rubbing against the shocks when the axles tilted. I'd already had one of the stock plastic shocks fall apart twice (I *hate* plastic shocks, they're never strong enough!), so I'd ordered a set of the factory-option aluminum shocks and some Mini-T rear springs to go with them. When I started to assemble the aluminum shocks, a solution suddenly hit me: I could space the lower shock mounts further outboard on the axles by bracing the shock mounting points with spare pivot-balls from the original shocks, and then using extra-long screws to secure the shocks out beyond the shock mounting points. This gave just enough extra clearance that the upper links no longer impacted the shocks (especially in the front), and also improved torque-twist a little bit.
There were still more issues to sort-out, though. The stock center driveshafts were plastic slider-type axles, and the sliding parts fit pretty loosely too. That was no good. After some searching and an accidental order of the wrong part, I eventually figured out that eRacingPro makes (or at least sells) steel center driveshafts for the Losi MRC, and they fit on the Slickrock just fine too.
I also found 3Racing steel CVDs to put on the front axle, to get rid of the uneven wear inherent in the dogbone-style joints the front axles originally used. (the rear axles also use dogbones, but since they don't steer, there was no need to upgrade them -- the rear dogbones are enclosed in the axle housing, greased thoroughly, and will probably never wear out.)
Oh, and I managed to scrape together a set of factory-option steering knuckles, the inner parts intended for the Slickrock and the outer parts intended for the Losi MRC. The anodizing isn't an exact match between the inner and outer parts, but it's close enough that I don't care. The rear axles still have the stock plastic lockouts, but they don't have to do any of the hard work, so that's fine.
There's something I can't show you, because it's buried inside the front axle, but it's really cool that someone figured out this would work: I replaced the front diff pinion with one from a MERV, which has 15 teeth instead of 14, so it gives about a 7% overdrive to the front axle -- not a huge amount, but every little bit helps. I installed the MERV diff pinion with a 1mm-thick spacer behind it to achieve the correct positioning, and the set-screw on the center driveshaft tightened right up against the thru-hole in the back end of the MERV pinion shaft. I instantly noticed an improvement in steering, because the front wheels are able to rotate faster, which is necessary when turning corners. I suppose it also helps a bit with climbing, but frankly just improving the turning radius is a good enough reason for this mod.
At this point I was getting close to finishing the build, but I still had to do something about that stock servo. There wasn't anything *wrong* with it, per se, but stock servos are never very good, and plastic-geared servos on rock crawlers (even small ones) are just failures waiting to happen. Conveniently, Hitec has a new low-profile servo available that fits perfectly, with even more clearance behind it than the stock servo had, *and* Hitec appears to be admitting that the Futaba-style 25-spline design has won the battle -- this servo comes with a 25-spline arm-mount, so I didn't have to figure out how to replace the stock servo horn.
...except I did replace the stock servo horn, anyway. The original one steered fine, but it stuck way out in front of the servo, and often caught on rocks. That was no good. So I replaced it with an OFNA low-profile servo horn, and then while I was at it, I decided to try making new steering linkages as well. The stock plastic steering linkages were also pretty bulky and tended to hang-up on obstacles, so replacing them would improve overall clearance. I knew the aluminum rods I had used to make the upper links wouldn't be strong enough to withstand getting smacked into rocks, so I decided to go with steel instead. Not trusting my bending and threading tools to handle steel rods without breaking, I opted for pre-threaded rods -- and then I carefully ground-off the threads from the exposed parts of the steering linkages, then chucked the linkages into my Dremel so I could smooth them out with emery paper. Let me tell you how much fun THAT was. Yeesh. It came out well, though.
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