1LikesBuild Complete: Traxxas Mini E-Revo
11-23-2014, 07:53 PM
#1
Build Complete: Traxxas Mini E-Revo
This one's been a long time coming.
When I first got into RC and I was researching my first vehicle purchase, the Mini E-Revo was one of the vehicles that appealed most to me. In retrospect, years before when I was just reading RC magazines but wasn't rich enough to buy anything, the full-size E-Revo looked cool to me back then too. There's something about the "monster-truggy" layout that looks perfectly optimized for hard corners at high speeds, while still having enough suspension clearance to avoid smashing to bits when it runs over a crack in the pavement.
However, after reading horror story after horror story about the MERV, I decided to get something else -- a Losi Mini Desert Truck -- instead. A year and a half later, and after lots of evenings spent reading, I finally felt ready to take on the challenge of building a MERV that wouldn't suck. This is what I came up with.
Most of the horror stories I read centered around the drivetrain, so straightaway I replaced almost all the drivetrain parts -- out came all of the stock gears and driveshafts, and in went Hot Racing hardened-steel transmission gears, Hot Racing hardened-steel diffs, and Traxxas axle and center-driveshaft CVDs. Oh, and I installed bearings in the rocker-arms for the shocks and the center pivot of the steering assembly before the vehicle ever moved under its own power, because it was such a simple mod there was no reason to postpone it.
Because I wasn't looking for a vehicle that can do backflips all day long (for that I have a HPI Savage XS), I also replaced the transmission output gear with a center diff filled with 100,000wt oil, and I installed a 540 brushed mod motor with 12x2 windings. The stock copper brushes in the motor were replaced with LRP silver brushes, soldered directly to the tabs on the endbell for maximum efficiency. The Team Orion brushed motor makes such a cool sound, I love it.
There was one snag when installing my Spektrum radio, though; it absolutely refused to communicate with the Traxxas brushed ESC. A quick trip to my local hobby shop netted a Dynamite brushed ESC originally intended for the 1/10 ECX Ruckus, and conveniently the color of the heatsink matched other parts on the vehicle. It was $50 I would've rather not spent, but oh well, at least it works well.
I also read horror stories about the chassis breaking where the differential cases attach, and as complex as this vehicle is, I didn't want to have to take absolutely everything apart so I could replace the chassis. TheToyz was selling reinforcing beams that bolt to the upper shock mounts, so I decided to install a couple of those as an insurance policy.
The shocks were a problem, as everyone knows, so I rebuilt those too as soon as I decided on suitable parts. The shocks were rebuilt with Hot Racing aluminum bodies, which have screw-on lower caps so I could really cinch-down the O-rings to prevent leaks, Traxxas stanchions coated with TiN to reduce wear (the stock stanchions were already showing some polishing by the time I got around to rebuilding the shocks), blue-stripe springs and 2000wt oil in the front, and pink-stripe springs and 3000wt oil in the rear.
Somewhere around the same time, I got sick of the stock tires. I spent about 5 minutes selecting the tires (Pro-Line Trenchers) and about a week selecting the wheels, because I didn't want the Desperado or Titus wheels most people use, but other options were really hard to find. Eventually I stumbled on a version of DE Racing's Trinidad wheels which were purpose-made for the MERV, so I went with those. I think they have a nice combination of sleek and strong appearance.
Having nailed-down the drivetrain and shocks, I set about improving the durability of the suspension and steering. When I turned the stock servo back and forth, I could hear one of the gears rubbing against the inside of the case, and I knew that wouldn't last very long. I replaced the servo with a Hitec HS-5085MG, which wasn't quite a perfect fit, but the bash-guard around the servo horn is made of soft plastic, so when I tightened-down the mounting screws, the bottom of the bash-guard just conformed to the shape of the little reinforcing bits that stick up off the front surface of the servo's mounting tabs. The new servo needed a new servo horn, and Hot Racing provided yet another part I needed.
I also swapped in a set of RPM A-arms, front and rear; no idea if they're really better than the stock A-arms, but enough people complained about the stock A-arms that I decided to do it anyway. (really, most of the mods I made to this vehicle were preventative in nature.)
In stock form, the handling was very twitchy. I know the toe-alignment can be changed by adjusting both the upper and lower pillow-ball in or out at the same time, but I wanted to be able to adjust toe independent of camber, so I went ahead and bought the adjustable toe-links anyway. (I also bought the metal shock pushrods so everything would match.) After adding a bit of camber-in and toe-out to the front wheels, the handling got a lot more stable, without losing its sharpness, because the camber-in means the outside front tire will bite harder in corners.
After driving the vehicle around a bit more, I realized it was much more likely to roll-over when I turned one direction than when I turned in the other direction. After puzzling about this for a while, I realized it was probably because the chassis was unbalanced, with only a single battery on the left side. So, I weighed the battery, cut off a suitable number of chunks of lead ballast, and stuck them inside the right-side battery compartment. Between the alignment adjustments and the addition of ballast in the empty battery compartment, the vehicle suddenly felt a lot more planted.
The last upgrade the vehicle needed was new steering knuckles. The stock knuckles had varying amounts of slop, with one of them actually binding a bit, so I knew I needed something adjustable. I was originally going to get aluminum knuckles, but then I thought the better of it, because I couldn't see a way that the aluminum knuckles and the steel pillow-balls wouldn't end up grinding against each other when the knuckles were adjusted for zero slop. So instead, I got the RPM knuckles, in blue, because I figured why not show off a little bit? Now that the RPM knuckles are installed and adjusted, there is no slop anywhere in the suspension, and the vehicle handles like it's on rails.
The MERV needs a lot of work, like pretty much everyone says, but when suitably upgraded it's a great vehicle. I think this one will stay in my collection for a long time.
When I first got into RC and I was researching my first vehicle purchase, the Mini E-Revo was one of the vehicles that appealed most to me. In retrospect, years before when I was just reading RC magazines but wasn't rich enough to buy anything, the full-size E-Revo looked cool to me back then too. There's something about the "monster-truggy" layout that looks perfectly optimized for hard corners at high speeds, while still having enough suspension clearance to avoid smashing to bits when it runs over a crack in the pavement.
However, after reading horror story after horror story about the MERV, I decided to get something else -- a Losi Mini Desert Truck -- instead. A year and a half later, and after lots of evenings spent reading, I finally felt ready to take on the challenge of building a MERV that wouldn't suck. This is what I came up with.
Most of the horror stories I read centered around the drivetrain, so straightaway I replaced almost all the drivetrain parts -- out came all of the stock gears and driveshafts, and in went Hot Racing hardened-steel transmission gears, Hot Racing hardened-steel diffs, and Traxxas axle and center-driveshaft CVDs. Oh, and I installed bearings in the rocker-arms for the shocks and the center pivot of the steering assembly before the vehicle ever moved under its own power, because it was such a simple mod there was no reason to postpone it.
Because I wasn't looking for a vehicle that can do backflips all day long (for that I have a HPI Savage XS), I also replaced the transmission output gear with a center diff filled with 100,000wt oil, and I installed a 540 brushed mod motor with 12x2 windings. The stock copper brushes in the motor were replaced with LRP silver brushes, soldered directly to the tabs on the endbell for maximum efficiency. The Team Orion brushed motor makes such a cool sound, I love it.
There was one snag when installing my Spektrum radio, though; it absolutely refused to communicate with the Traxxas brushed ESC. A quick trip to my local hobby shop netted a Dynamite brushed ESC originally intended for the 1/10 ECX Ruckus, and conveniently the color of the heatsink matched other parts on the vehicle. It was $50 I would've rather not spent, but oh well, at least it works well.
I also read horror stories about the chassis breaking where the differential cases attach, and as complex as this vehicle is, I didn't want to have to take absolutely everything apart so I could replace the chassis. TheToyz was selling reinforcing beams that bolt to the upper shock mounts, so I decided to install a couple of those as an insurance policy.
The shocks were a problem, as everyone knows, so I rebuilt those too as soon as I decided on suitable parts. The shocks were rebuilt with Hot Racing aluminum bodies, which have screw-on lower caps so I could really cinch-down the O-rings to prevent leaks, Traxxas stanchions coated with TiN to reduce wear (the stock stanchions were already showing some polishing by the time I got around to rebuilding the shocks), blue-stripe springs and 2000wt oil in the front, and pink-stripe springs and 3000wt oil in the rear.
Somewhere around the same time, I got sick of the stock tires. I spent about 5 minutes selecting the tires (Pro-Line Trenchers) and about a week selecting the wheels, because I didn't want the Desperado or Titus wheels most people use, but other options were really hard to find. Eventually I stumbled on a version of DE Racing's Trinidad wheels which were purpose-made for the MERV, so I went with those. I think they have a nice combination of sleek and strong appearance.
Having nailed-down the drivetrain and shocks, I set about improving the durability of the suspension and steering. When I turned the stock servo back and forth, I could hear one of the gears rubbing against the inside of the case, and I knew that wouldn't last very long. I replaced the servo with a Hitec HS-5085MG, which wasn't quite a perfect fit, but the bash-guard around the servo horn is made of soft plastic, so when I tightened-down the mounting screws, the bottom of the bash-guard just conformed to the shape of the little reinforcing bits that stick up off the front surface of the servo's mounting tabs. The new servo needed a new servo horn, and Hot Racing provided yet another part I needed.
I also swapped in a set of RPM A-arms, front and rear; no idea if they're really better than the stock A-arms, but enough people complained about the stock A-arms that I decided to do it anyway. (really, most of the mods I made to this vehicle were preventative in nature.)
In stock form, the handling was very twitchy. I know the toe-alignment can be changed by adjusting both the upper and lower pillow-ball in or out at the same time, but I wanted to be able to adjust toe independent of camber, so I went ahead and bought the adjustable toe-links anyway. (I also bought the metal shock pushrods so everything would match.) After adding a bit of camber-in and toe-out to the front wheels, the handling got a lot more stable, without losing its sharpness, because the camber-in means the outside front tire will bite harder in corners.
After driving the vehicle around a bit more, I realized it was much more likely to roll-over when I turned one direction than when I turned in the other direction. After puzzling about this for a while, I realized it was probably because the chassis was unbalanced, with only a single battery on the left side. So, I weighed the battery, cut off a suitable number of chunks of lead ballast, and stuck them inside the right-side battery compartment. Between the alignment adjustments and the addition of ballast in the empty battery compartment, the vehicle suddenly felt a lot more planted.
The last upgrade the vehicle needed was new steering knuckles. The stock knuckles had varying amounts of slop, with one of them actually binding a bit, so I knew I needed something adjustable. I was originally going to get aluminum knuckles, but then I thought the better of it, because I couldn't see a way that the aluminum knuckles and the steel pillow-balls wouldn't end up grinding against each other when the knuckles were adjusted for zero slop. So instead, I got the RPM knuckles, in blue, because I figured why not show off a little bit? Now that the RPM knuckles are installed and adjusted, there is no slop anywhere in the suspension, and the vehicle handles like it's on rails.
The MERV needs a lot of work, like pretty much everyone says, but when suitably upgraded it's a great vehicle. I think this one will stay in my collection for a long time.
Last edited by fyrstormer; 11-23-2017 at 01:32 AM.
11-26-2014, 08:06 PM
#2
After driving this vehicle a bit more, I've decided that as well-tuned as the suspension is, it still needs a front swaybar. So I bought the Hot Racing kit (I ended up with a lot of Hot Racing parts on this vehicle), and bolted it up.
There was only one small snag (there's always one), which was figuring out how to properly retain the swaybar since I'm not using the stock plastic reinforcing braces to support the top eyelets on the shocks. (I have chassis braces instead, but they're not the same shape.) That problem was solved by putting two small washers under the swaybar, to keep it in the little channel it's supposed to stay in. After some quick tweaking of the leverage on the swaybar, it now works very well, and it no longer lifts the inside rear tire in sharp corners.
There was only one small snag (there's always one), which was figuring out how to properly retain the swaybar since I'm not using the stock plastic reinforcing braces to support the top eyelets on the shocks. (I have chassis braces instead, but they're not the same shape.) That problem was solved by putting two small washers under the swaybar, to keep it in the little channel it's supposed to stay in. After some quick tweaking of the leverage on the swaybar, it now works very well, and it no longer lifts the inside rear tire in sharp corners.
Last edited by fyrstormer; 11-23-2017 at 01:33 AM.
11-27-2014, 02:13 AM
#3
Nice. What batteryes will you run/can you run with that motor? And is the ESC Li-Po compatible?
11-28-2014, 01:18 PM
#4
Yes, the ESC is LiPo compatible. It's a very simple ESC from Dynamite, with a jumper to specify NiMH or LiPo, and another jumper to specify forward/brake/reverse or forward/brake or crawler mode.
Still trying to get the swaybar tuned. It seems even a moderate amount of sway-resistance causes the vehicle to understeer a fair amount, so I'm trying to tune it for the least amount of sway-resistance I can get. I thought the Hot Racing swaybar kit came with swaybars of three different stiffnesses, but instead it appears they're just different colors.
Also, I reinstalled the stock diffs, shimming them as necessary, because the stock diffs have proper O-ring seals to keep silicone diff oil inside the diffs where it belongs. Since I'm not running massive power, I might not have needed the Hot Racing hardened-steel diffs after all. However, I will keep them handy, and sand-down the mating surfaces to make them as smooth and flat as possible, so they will seal better in the future. I may also cut some paper gaskets to help ensure proper seals if I ever use them again.
...aaaand I rebuilt the center diff again, this time filling it with fluorocarbon-gelled silicone grease instead of silicone oil. I went up to 100,000wt silicone oil in the center diff, but it eventually sheared down to a much thinner viscosity that wasn't useful for providing any limited-slip action. From what I've read, this is a fundamental problem with all thick silicone oils. Hopefully the fluorocarbon additives in the silicone grease I used will help it resist shearing better, and provide more consistent performance over the life of the center diff. If that doesn't work either, then I'll just go back to having no center diff at all, and let the slipper-clutch protect the drivetrain all by itself.
Last edited by fyrstormer; 11-28-2014 at 02:20 PM.
11-30-2014, 03:57 PM
#5
I got the swaybar tuned just-right. The bottoms of the linkage ball-studs are mounted 9mm above the bends in the swaybar. That seems to give the linkage just enough leverage to twist the swaybar and keep the front wheels both on the ground through corners, thus preventing massive understeer, while still allowing the swaybar to keep the vehicle from leaning too much and lifting the inside rear wheel off the ground, thus preventing massive oversteer.
11-30-2014, 04:19 PM
#7
It's a fantastic vehicle if you can just be reasonable with it. It handles the busted-up pavement in my apartment parking lot without so much as a butt-wiggle, it can jump speedbumps at full speed and land on its wheels, and it can drive on grass without being totally hopeless -- that's about the best possible performance you can expect from a 1:14-scale vehicle. (It's called 1:16, but I have other 1:16s and this is larger; Traxxas always underestimates the scale of their vehicles.)
People do all kinds of horrific stuff to their MERVs and then complain that they break too easily. Any time you pull a stunt involving 4S battery power and a skateboard ramp, and something *doesn't* break, you should feel lucky.
People do all kinds of horrific stuff to their MERVs and then complain that they break too easily. Any time you pull a stunt involving 4S battery power and a skateboard ramp, and something *doesn't* break, you should feel lucky.
12-02-2014, 07:53 AM
#8
Looks fun, nice pics too
12-20-2014, 07:21 AM
#9
Tech Addict
It's a fantastic vehicle if you can just be reasonable with it. It handles the busted-up pavement in my apartment parking lot without so much as a butt-wiggle, it can jump speedbumps at full speed and land on its wheels, and it can drive on grass without being totally hopeless -- that's about the best possible performance you can expect from a 1:14-scale vehicle. (It's called 1:16, but I have other 1:16s and this is larger; Traxxas always underestimates the scale of their vehicles.)
People do all kinds of horrific stuff to their MERVs and then complain that they break too easily. Any time you pull a stunt involving 4S battery power and a skateboard ramp, and something *doesn't* break, you should feel lucky.
People do all kinds of horrific stuff to their MERVs and then complain that they break too easily. Any time you pull a stunt involving 4S battery power and a skateboard ramp, and something *doesn't* break, you should feel lucky.
03-12-2016, 10:21 PM
#10
Nothing new to show on this truck, but I did just finish replacing all the ball bearings with Boca Yellow Seal ceramic bearings. The stock bearings were 2 years old and it was time to bite the bullet and upgrade them. The new bearings will last a very long time.
Also, as long as I had the gearbox open, I briefly tried running the MERV without a center diff, and the handling sucked. It understeered too much when accelerating and oversteered too much when braking, and cornering wasn't nearly as smooth as before. So I quickly put the center diff back in, and it's much better again.
Also, as long as I had the gearbox open, I briefly tried running the MERV without a center diff, and the handling sucked. It understeered too much when accelerating and oversteered too much when braking, and cornering wasn't nearly as smooth as before. So I quickly put the center diff back in, and it's much better again.
03-15-2016, 11:51 PM
#11
I too purchased a brushed edition Merv about 3 years ago.
Immediately ditched the stock motor and esc and went with a 1/10 BL combo from Hobbywing. More specifically a 35A ESC with the 9T 4300kv motor.
I run two 1800mah packs in parallel and get around 40 minutes of runtime. A 1/10 system in this small of a truck is INCREDIBLY efficient. Thanks to the big - block motor mount from Traxxas being a factory option in the brushed models, this was a painless transition.
Only recently did I start having range issues with the factory am TQ radio from TRX. 3 days ago I ordered the new TRX 2.4 TX/RX combo with the "link" compatability. Pretty excited to get that installed and get it back operational again.
I have the factory merv wheels and tires, a PL road rage premounted combo, and I recently snatched up some factory mini-summit factory premounted wheels/tires from Tower Hobbies. Use the summit combo for offroad bashing sessions and I've been pleased with their application on my merv. Also gave me a touch more ground clearance. Which is handy while bashing.
When properly geared, I've topped the merv out at 56mph. This is while following it down a nice smooth highway in my truck while the wife drives. Even then, the electronics were cool to the touch. Remember, it's a 1/10 system I'm using. Unfortunately, I've run out of room to run a bigger pinion without making some serious modifications to the chassis or motor plate. Which I'm not interested in doing.
I do agree with you though. The merv needs a fair amount of attention out of the box to make it a worthwhile vehicle. At least for the seasoned hobbyist.
I also have a Losi Mini 8ight T that I'm in the process of modifying. It's much more "track oriented" than the Merv. So I anticipate I'll have much more top speed out of it than I can currently attain with my merv.
Immediately ditched the stock motor and esc and went with a 1/10 BL combo from Hobbywing. More specifically a 35A ESC with the 9T 4300kv motor.
I run two 1800mah packs in parallel and get around 40 minutes of runtime. A 1/10 system in this small of a truck is INCREDIBLY efficient. Thanks to the big - block motor mount from Traxxas being a factory option in the brushed models, this was a painless transition.
Only recently did I start having range issues with the factory am TQ radio from TRX. 3 days ago I ordered the new TRX 2.4 TX/RX combo with the "link" compatability. Pretty excited to get that installed and get it back operational again.
I have the factory merv wheels and tires, a PL road rage premounted combo, and I recently snatched up some factory mini-summit factory premounted wheels/tires from Tower Hobbies. Use the summit combo for offroad bashing sessions and I've been pleased with their application on my merv. Also gave me a touch more ground clearance. Which is handy while bashing.
When properly geared, I've topped the merv out at 56mph. This is while following it down a nice smooth highway in my truck while the wife drives. Even then, the electronics were cool to the touch. Remember, it's a 1/10 system I'm using. Unfortunately, I've run out of room to run a bigger pinion without making some serious modifications to the chassis or motor plate. Which I'm not interested in doing.
I do agree with you though. The merv needs a fair amount of attention out of the box to make it a worthwhile vehicle. At least for the seasoned hobbyist.
I also have a Losi Mini 8ight T that I'm in the process of modifying. It's much more "track oriented" than the Merv. So I anticipate I'll have much more top speed out of it than I can currently attain with my merv.
03-16-2016, 03:59 AM
#12
One of the best RC in small scales.
An item for sure to anyone interested in RC's. Beginners,Trackers,Speeders,Bashers,Weekend racers...whatever...
It needs a love to be on top condition like an High End 1/8 buggy...but after that is solved... they ROCK!
Here is mine:
An item for sure to anyone interested in RC's. Beginners,Trackers,Speeders,Bashers,Weekend racers...whatever...
It needs a love to be on top condition like an High End 1/8 buggy...but after that is solved... they ROCK!
Here is mine:
03-16-2016, 08:03 AM
#13
Tech Rookie
Really awesome builds guys! I have recently bought a Merv and plan on beefing it up in a similar fashion. I'm considering upgrading to 1/10 scale motor. Which plate are you all running?
03-16-2016, 01:29 PM
#14
The factory "big block" plate supplied by Traxxas on the brushed models has been more than adequate for me.
04-22-2017, 12:34 PM
#15
I did some work on my MERV yesterday, for the first time in a long time. First of all, I replaced the tires because the old ones weren't gripping very well anymore.
I actually bought these tires by mistake, thinking they were normal stadium-truck-sized tires, and while they are the correct width they're definitely not as tall as normal stadium-truck tires. I was going to send them back, but I noticed they were the same height as 1:10 buggy tires, and then I got curious. I got a set of HPI wheels and test-fit them on my MERV, and they looked great. They're made of HPI's "pro" compound, so they stick well too.
Also, since this vehicle has slowly gotten faster and heavier over the years, I decided it was time to bite the bullet and wire it for two batteries, because the single battery I was using before was getting uncomfortably hot. This rats-nest of wiring is the best I was able to do to keep the 2x2S parallel wiring under control.
Lastly, since being heavier and going faster means the *motor* has to work harder also, I decided it was time to see if I could shoehorn an endbell fan under the MERV body. I figured out I could do it if I cut off one of the corners, which was no big deal since I didn't need that corner for mounting purposes anyway.
As you can see, like everything else on this car, it just barely fits. I'll need to replace the piece of foil tape I added, which is supposed to protect the body from rubbing by the battery plug, with a piece of felt to protect it from the sharp edge of the fan instead. That's how hobbies work, right? The rabbit hole goes as deep as you want it to go.
I actually bought these tires by mistake, thinking they were normal stadium-truck-sized tires, and while they are the correct width they're definitely not as tall as normal stadium-truck tires. I was going to send them back, but I noticed they were the same height as 1:10 buggy tires, and then I got curious. I got a set of HPI wheels and test-fit them on my MERV, and they looked great. They're made of HPI's "pro" compound, so they stick well too.
Also, since this vehicle has slowly gotten faster and heavier over the years, I decided it was time to bite the bullet and wire it for two batteries, because the single battery I was using before was getting uncomfortably hot. This rats-nest of wiring is the best I was able to do to keep the 2x2S parallel wiring under control.
Lastly, since being heavier and going faster means the *motor* has to work harder also, I decided it was time to see if I could shoehorn an endbell fan under the MERV body. I figured out I could do it if I cut off one of the corners, which was no big deal since I didn't need that corner for mounting purposes anyway.
As you can see, like everything else on this car, it just barely fits. I'll need to replace the piece of foil tape I added, which is supposed to protect the body from rubbing by the battery plug, with a piece of felt to protect it from the sharp edge of the fan instead. That's how hobbies work, right? The rabbit hole goes as deep as you want it to go.
Last edited by fyrstormer; 11-23-2017 at 01:34 AM.