Mojave Learning with the Mojave EXB

[Knightfall]

Last year I got back into RCs after over a decade. Prior, I owned an HPI Savage with a nitro engine. I found nitro engines to be a PITA to run and sold the RC. I bought an Arrma Typhon MEGA and got the bug after seeing how fast and fun electric RCs are, albeit rather quiet compared to the nitro RCs. I picked up a Big Rock and a Vorteks over time, and now I've made the step into the larger 1/7th scale with the very hyped-up Arrma Mojave. With thanks to the community here and a few groups on Facebook, I made the choice to get the EXB and buy my own electronics.

From owning the Vorteks, I really liked the ecosystem from Spektrum. Yes, I had trouble with my Firma 100a ESC and an LVC issue which I blame for causing one of my Spektrum 3s batteries to have a bad cell. (11 ohms on one cell after 4 months of owning it.) However, I learned how to fix that problem and potentially avoid the issue with other products. I'll explain that later.

I learned that getting better gear and not pushing it to the limit can help with longevity. And so, I went with the Spektrum Firma 160a ESC and 1250 kV motor to run on 6s, even though it's 8s capable.

The servo is a Savox SW-1210SG, chosen as a suggestion by my local hobby shop. I later learned the Firma 160a does not have BEC for 7.4v. Only 6.0 and 8.4, even after a firmware update. So my Savox isn't at its full potential, but I'm having zero issues with it after 5 runs. In fact, I found it to be far faster and stronger than the Amazon 25kg deal I have for my Vorteks.

I went with a 23t pinion to run with. My LHS didn't have a 22t in stock which seemed to be a popular choice, but the 23t is doing well for me. No heat issues. Certainly enough torque, and fast. See the one issue in the picture? This is when I put the pinion on thinking it was aimed the same way as my Vorteks and Big Rock. Oops. Thankfully the dab of Blue Locktite didn't set yet and was easy enough to remove and swap around properly.

The Firma 160a ESC took me a bit to figure out how to mount in my Mojave. This thing is huge compared to the 100a ESCs in my 3s Arrmas! I've seen people online would cut off the side tabs to make it fit, or put a huge zip tie right over the whole thing. What I did was put the double-sided tape onto the mounting plate that comes with the Mojave EXB and squished in the ESC slowly and let it sit where it wanted to sit. Then I unscrewed the mounting plate and removed the ESC and plate together. Once I had it in hand, I could see two of the mounting tabs on the ESC were rather close to holes in the mounting plate. So I just took two zip ties and tied two points together. I never took pics while I was doing this, sorry, but here are pics once it's all in place.

As you can see from the dirt, this has been bashed about 5 times, 25-30 minutes per time, over very rough terrain, and that ESC has not budged. The double-sided tape and those zip ties are holding it very well. Plus it's really snug in there, so little room to wiggle.

From owning the Vorteks and having issues with my Firma 100 ESC, I've learned the importance to pick up the Spektrum Program card and update the firmware.

Just like my Firma 100a, 130a, and now my 160a, there was an update waiting to be loaded. I, unfortunately, cannot tell you the difference between before and after this update on my 160a because I did it before I even ran the RC. But with my 100a and 130a, new features such as BEC settings did appear that weren't there, as well as different defaults, such as timing.

I encourage all to look into updating the firmware on their electronics. I believe you can do with this Hobby Wing and maybe Castle as well.

To protect what I can, I've added foam to the bumpers and mounting points which have been suggested by nearly everyone I see with a Mojave and added Gorilla Tape to the inside of the Mojave body. (I've done the drywall tape and Shoo Goo on my Vorteks. That is far too tedious and no one seems to talk about the lingering smell!)

I ordered Scorched fenders last night and looking forward to putting those on and hopefully reducing the amount of debris I find in my Mojave after every run. The thing is a lawnmower in the grass and a Hoover on gravel.

 

[Knightfall]

I forgot to mention my radio/receiver!

Because my Typhon MEGA became a parts car for my Big Rock and Vorteks, I had an extra radio and receiver. But I really love the Spektrum DX3 with the telemetry and AVC. So I pulled those electronics from my Vorteks and put them in my Mojave EXB. Then I put the Typhon's electronics in my Vorteks.

Now my Mojave EXB has telemetry and AVC.

Also, the EXB comes with a 23t servo horn, not a 25t. So I picked up a Power Hobby Aluminum Fixed Link. It replaced not just the servo horn, but the other segment between the horn and the steering. (Again, please pardon the dirt. I've already had a lot of fun with this.)

 

[KnowAir]

Nice build! Nice write up too. Must be an animal with that combo in it?
I run mine on a cheapo rtr 150a esc with a 10 year old tenshock 4274 (2200kv) and it's a blast for me. I've found 5s to be perfect for what I do.
Enjoy that awesome rig!!

Edit: I love it! Just to show how different we can be, here you (and many others) are enjoying the modern luxuries of telemetry and AVC.. meanwhile, the caveman that is I, am using 15 year old tech and disabling LVC so I can run 5s!!
What a great and diverse community we have here at AF!

 

[Knightfall]

Nice build! Nice write up too. Must be an animal with that combo in it?
I run mine on a cheapo rtr 150a esc with a 10 year old tenshock 4274 (2200kv) and it's a blast for me. I've found 5s to be perfect for what I do.
Enjoy that awesome rig!!

5s? That's a rare one from what I've seen. I don't have any other 4, 5, or 6s RCs, so I'm sure even an RTR Mojave would have blown me away!

This thing isn't pulling wheelies or anything which I have seen Mojaves do online. It's probably due to the 23t pinion and 6s, while others have 8s and maybe even geared down. I might pick up a 19t or 20t to see how it acts and if I'm still happy with its top speed.

 

[KnowAir]

Yes, 5s is not really a thing TBH. I have this distorted perception that 4s isn't enough(true), and 6s is too much (likely untrue).. For whatever reason, I just like the way it drives on 5s, also worth mentioning that I have a crap load of 3s and 2s packs, which makes 5s an attractive option..
The wheelie'n mojave seems to be mainly on 8s from what I've seen.

 

[Knightfall]

Yes, 5s is not really a thing TBH. I have this distorted perception that 4s isn't enough(true), and 6s is too much (likely untrue).. For whatever reason, I just like the way it drives on 5s, also worth mentioning that I have a crap load of 3s and 2s packs, which makes 5s an attractive option..
The wheelie'n mojave seems to be mainly on 8s from what I've seen.

Good info about 5s. Cool to know.

So you can combine a 2s and 3s pack? I thought packs always had to be the same. Or maybe just the mAh and discharge rates?

 

[KnowAir]

just the mAh and discharge rates?

These are the important specs that need to match

 

[KnowAir]

I should ad that it's probably a good idea to use batteries from the same manufacturer as well. There is no standardized protocol that the manufacturers adhere to, well are held to, I should say. They can pretty much rate them however they want. Of course they're all "the best"..self proclaimed, that is!

 

[Hector_Fisher]

I should ad that it's probably a good idea to use batteries from the same manufacturer as well. There is no standardized protocol that the manufacturers adhere to, well are held to, I should say. They can pretty much rate them however they want. Of course they're all "the best"..self proclaimed, that is!

LOL, apparently @KnowAir is all over this forum lately answering all kinds of questions about 5s!

 

[KnowAir]

LOL, apparently @KnowAir is all over this forum lately answering all kinds of questions about 5s!

Yes, and sorry? This is what happens when I'm bored at work I guess..
If one wants to run 5s properly, I believe Castle esc's support it, however I've never owned any Castle stuff cuz I'm cheap or poor. Or both.
Hobbywing has the Xerun esc's that has settings for it as well. Don't quote me, but I think even the lowly HW Quicrun WP-8BL150 supports it, which sells for about $100. Only the Hobbywing version tho, not an rtr version.
Or, disable LVC and run a lipo alarm.

 

[Knightfall]

Update: Not quite optimal.​

After noting my MEXB is running a bit slower than my Vorteks, I created another thread asking if my setup is optimal. It turns out through discussion that because of my 1250kv motor on 6s, I have the torque, but not the top speed, and I'm running roughly 8-10 MPH slower than the RTR Mojave. So I need to gear up from my 23t pinion to around 27t.

Well, ironically, I cannot go higher than 23t because the EXB has a different centre diff, and a 26t spur won't fit properly. My options are:

1. downgrade to a diff from something like the Infraction ($70 CAD)
2. Await and see if someone makes a 46t spur that fits the EXB diff
3. Get a new motor mount that would allow more space for a larger pinion ($70-100 CAD)
4. Do what I saw TomleyRC do on YouTube and lengthen the hole in the EXB mount a few millimetres to buy myself more room

At this time, my LHS thinks they found me an option or two and said they'll be here around Friday this week. No charge if it doesn't fit, but if it does, great!

Update: PowerHobby fans​

In anticipation of gearing up to add some top-end speed, and with Scorched Fenders on the way, I know heat could be an issue. So I picked up a PowerHobby heatsink and dual fan set. The heatsink isn't meant for a 1/5 scale motor like mine, but because of its clamp style and flexes easily, it fits very well and doesn't budge.

The Firma 160a comes with a lead off of it for fans, and with a y-adapter, I connected it all together. I've run it twice now and it ran well. Temps never went over 110 F, during 26 C (78.8 F) weather.

 

[KnowAir]

Or..you could run it on 8s. That will bring the speed up. I'm not familiar with fitting 8s into a mojave, but there's plenty here that have.

 

[Sandracer_NL]

Option 1 and 3 are pretty expensive for what you get IMO, especially since option 1 is a downgrade.
Option 2 is available by Vitavon.
Option 4 if you think you can pull it off.
Option 5 is run 8s like @KnowAir mentioned above, but it will make the Mojave considerable heavier.
Option 6 is sell the Spektrum motor or combo and get the 4985 Hobbywing motor or Max6 combo.

 

[Hector_Fisher]

Or..you could run it on 8s. That will bring the speed up. I'm not familiar with fitting 8s into a mojave, but there's plenty here that have.

Agreed, that is a motor intended for running 8s, not 6s. So something is going to have a change on your rig to run at "regular" speeds. Either choose one of the methods you listed above to swap to a bigger pinion, or run 8s. That's the only thing I can think of.

Option 1 and 3 are pretty expensive for what you get IMO, especially since option 1 is a downgrade.
Option 2 is available by Vitavon.
Option 4 if you think you can pull it off.
Option 5 is run 8s like @KnowAir mentioned above, but it will make the Mojave considerable heavier.
Option 6 is sell the Spektrum motor or combo and get the 4985 Hobbywing motor or Max6 combo.

^^^ yeah this too

 

[KnowAir]

Not saying the 1250kv is a bad choice, but not ideal for 6s..motor kv is chosen by the manufacturer or builder based on input voltage amongst other things.. 1800-2000kv would be a more suitable rpm for a 6s rig with a diff ratio like Arrmas. I wouldn't go below say 1600kv for a 6s rig as it creates gearing limits as you've already discovered. 2200kv would be max for 6s, as a suggestion at least.

 

[KnowAir]

My suggestion is either run it on 8, or get the HW 4985. Depending on your finances, maybe keep the 1250kv for a future rig.

 

[Knightfall]

Or..you could run it on 8s. That will bring the speed up. I'm not familiar with fitting 8s into a mojave, but there's plenty here that have.

I suppose I didn't mention the intent was to stick with 6s for longevity and avoid spending money on new 4s batteries. But you're absolutely right, 8s would wake up this setup without a doubt. I've seen Mojaves wheelie on 8s.

My suggestion is either run it on 8, or get the HW 4985. Depending on your finances, maybe keep the 1250kv for a future rig.

Well, I just got everything recently, so purchasing another motor isn't in the cards right now. I do agree what would work.

See my prior reply about 8s. Maybe one day, but I don't have any 4s batteries, just 3s.

 

[rcaddic88]

I run that motor in my Kraton xl, essentially the mohave with krytron arms and larger tires, its been awesome. Doesn't run hot on the lighter 7th scale rigs and the power is sublime! I run the 4985 same max 6 on my mohave Exa and the 1250 on 8s is much more powerful then the 4985 on 6s based on my experience.
I'm sure theres others, but RC power makes an excellent 5000 MAH 4 cell that a pair of fit perfectly in the 6s battery box, its usually hard to fit most 4s brick pairs in them. I circled them in red in my 4s battery draw, I have 4 of them because they work in a few harder to fit rigs liek the max and max as well as the 6s Arrma.

 

[Knightfall]

Update: StupidRC motor mount​

Someone locally was selling this motor mount for cheap. It fits the EXB LSD perfectly but I was surprised to learn the Spektrum 1250 kV doesn't quite fit it without modification. I ended up having to drill out the holes a little with a cobalt drill bit and use my Dremel to smooth it out. Apparently, the holes need to be 30mm apart, it looks like the 1250's holes are around 28-29mm. But it's in now! Therefore I could gear up from the 23t pinion and put in a 27t pinion.

After a 20-minute session of some high-speed passes, zipping through gravel and dirt, I can safely say I'm very happy with the performance. It's certainly faster (as it should be) and still has loads of torque available. Reminder: I run 6s, not 8s.

I checked the temperature too of the motor frequently and it never went over 120F during the 22C (72 F) weather.

Update: ...Deadpool?​

I'm a Deadpool fan and do some graphic design in my career. I had some fun one lunch hour and made these for my MEXB.

These won't last with how hard I drive my RC, but it's just for fun.

 

[KnowAir]

Update: StupidRC motor mount​

View attachment 229439

Someone locally was selling this motor mount for cheap. It fits the EXB LSD perfectly but I was surprised to learn the Spektrum 1250 kV doesn't quite fit it without modification. I ended up having to drill out the holes a little with a cobalt drill bit and use my Dremel to smooth it out. Apparently, the holes need to be 30mm apart, it looks like the 1250's holes are around 28-29mm. But it's in now! Therefore I could gear up from the 23t pinion and put in a 27t pinion.

After a 20-minute session of some high-speed passes, zipping through gravel and dirt, I can safely say I'm very happy with the performance. It's certainly faster (as it should be) and still has loads of torque available. Reminder: I run 6s, not 8s.

I checked the temperature too of the motor frequently and it never went over 120F during the 22C (72 F) weather.

Update: ...Deadpool?​

I'm a Deadpool fan and do some graphic design in my career. I had some fun one lunch hour and made these for my MEXB.

View attachment 229440

View attachment 229441

View attachment 229442

These won't last with how hard I drive my RC, but it's just for fun.

Sweeet! Glad you got it sorted out! Nice, thinking outside the box too