Power recommendation for SMT10?

[Mad Ax]

I'm lining up my next big build - an SMT10 with RH Designs 12.5" wheelbase kit and sway bars, Clod-size wheels and JConcepts body.  I'm going to build in a racing configuration as per a Trigger Kings video I've seen, but as there's no solid axle racing around these parts it will only be run around fields and gravel roads and the odd shale beach trip.

I'd rather reliability over all-out speed.  I don't want to be replacing axles every other week.  I'm not looking to spend big bucks on an all-singing system, just something I can throw in a battery and go play.

I run my TXT-1 on 3S with Etronix 19T Sport Tuned motors, I'd really like something that's a little bit faster (there's got to be a hierarchy in my fleet  ) but not crazy fast.

I'm guessing a brushless combo is the way to go here, I can run on 2S or 3S, whatever is going to give the best results for the money.  I know there's loads of cheaper Chinese systems these days but I have no idea what brand is what, what's worth buying and what's worthless junk.  I've used Hobbywing systems and I rate them, I've had various Turnigy combos over the years and although I've had one or two ESC failures they seem good value.

I don't really know what KV rating I should be looking at and if I should choose a KV rating with 2S or 3S in mind, and if I should be looking at a 540 size or if I need to go bigger for a truck of this size.

I'm thinking @87lc2 is probably the expert here

[MadInventor]

My 2 cents, I've  fitted a hobbywing 1/8 2000KV combo (4274 sized motor) in my TXT-1, and it's pedestrian on 2S (Probably a little bit better than silver cans), is about right on 3S, but here's the thing, you can also run it on 4S if you're feeling adventurous.

I tried it by simply stacking 2 x 2 Cell lipo in it with and appropriate wiring adapter and it was ferociously torquey.

I think these are great motors for 1/10 monster trucks, as they have bags of torque being a larger motor (4274 as supposed to 3650), still have the same bolt pattern as a 540, and when you run them they're quiet and don't get hot at all as they are so under stressed. (Ideal if you're going to be braking and accelerating a lot if you can find someone to race against) You can also gear them up without having to worry about overheating like you would with a 3650 (I was running mine on 15T pinions, and I think the TXT box will take 20T pinions).

Yes the hobbywing systems are pricey, but as you say, they're reliable, and I rate them as well. You can always go for a Hobbywing ESC and a turnigy motor to bring the price down a bit. I used hobbywing ESCs and turnigy motors in my Skidder and the War Rig and they seem to work well together with no issues.

When I bought my system, 2000KV was the only available option, but now the 4274 motor seem to be available in 2000 > 2400 KV. If you think you might want to use 4S then I definitely wouldn't get anything more than 2000KV.

[Mad Ax]

Interesting point.  2000KV instinctively feels very low for someone accustomed to 1:10 on 2S, but I guess that's the equivalent of 4000KV on 2S if I run it on 4S, and as you say, very understressed.  I don't have any 4S packs but I could chain two 2S packs.  The bonus there is my 2S packs are hardcase and my 3S are softies, so I can't run 3S and most UK tracks.  On the flipside I'd need to mount 2 packs in the chassis, and I'm not sure what mounting options are like under the SMT10.

I might consider the higher KV system and run on 3S, but in the tradition of Stack Overflow, I will wait for more answers before marking one as correct

[Bash]

I'd go with a 550 size brushless motor since it is a good balance of weight and power. These are available in nearly any KV rating that you want, but for 2s I'd say around 4600-4000 kv is perfect, 3300-3000 on 3s and 2400-1800 for 4s. Personally, I'd go for a 3s setup as it is more efficient than a 2s setup and not as pricy as 4s. I'm not too certain that a 1/8 size motor is the right choice for an SMT10, since they are fairly lightweight, and those motors weigh a lot more than a normal 1/10 motor.

[OldSchoolRC1]

If you don't want to be replacing axles, I'd avoid 4S. The internals are just not up to it unless you want to spend a fortune on hard gears, VP CVD's and axles, and aluminum axle housings. Their origins date back to HPI's nitro 1/10 days. Clod tires and locked diffs are especially hard on the axles. 

I run mine on a 3200kv 550 (Orion motor, HW ESC) and 2S. It's not super fast, though I'm sure it would be with more volts, but it's very torquey.  Very monster truck-ish and so far I'm happy with it. I started with a Holmes Revolver which had gobs of torque, but not a lot of speed. Regardless of volts, a 550 can is the way to go imo, the truck is somewhat heavy. 

I also use open diffs front and rear and 2.2 Destroyers to minimize the breakage. So far, no issues! I have clod tires on standby, just haven't installed them yet.   

[87lc2]

Nice to see you're finally getting the SMT10 together, they're fun trucks, but fragile at times.  As long as you drive them sensibly (not 100% throttle all the time) they hold up pretty well.  Like MadInventor I have run 1/8 scale brushless systems on my TXT based trucks and they are really nice.  On 2S they are quite slow, but the motor never gets warm and there's tons of torque.  On 3S they are a lot better and still stay nice and cool.  However, I don't think I'd personally recommend a 1/8 scale brushless system on the SMT10.  I don't think the axles (especially the differential gears) would handle that type of torque.  Not to mention the stock driveshafts, which I really like, but they would probably get twisted pretty quick with that much torque.  I wouldn't even think of running a 1/8 system on 4S, you;re just asking to twist the truck up going that route.

I have a few SMT10s and am currently running the following setups:

1) Castle 4600kv brushless system; I run stock 14/56 gearing on this truck and on 2s it's pretty quick, on 3s it flies.  I have driven it carefully and it's held up well so far.  Motor stays pretty cool, so may go to a 15 or 16 tooth pinion and see if I can get the speed I'm looking for on 2S.  This truck runs on Clod-sized tires (Proline Decimator)

2) HW 1080 ESC with 17t 3-slot Reedy Radon 2;  Running 16/56 gearing on this truck and I really like it, basically a Sport Mod setup.  Probably not as quick as the brushless truck, but it feels like a good combo.  The Radon does get a bit hot on 3S so I mostly just run this on 2S as a more realistic truck.  Since I mostly use senorless brushless system s in trucks like these, the brushed combo does feel a lot smoother.  This truck runs on Clod sized tires (JConcepts Renegade)

3) HS 1080 ESC with 12t 500 brushed motor;   Running 17/56 gearing on this truck.  This is pretty much what the stock SMT10 comes with, with another couple teeth on the pinion.  This is my "basher" setup as the 550 motor provides some more torque and takes to 3S power very nicely, motor barely gets warm.  This truck runs on larger 2.2 tires (Duratrax Munition).

 

I have tried other combos but that's what I'm running at this time.  Brushless is nice, but I would honestly recommend a 550 brushed motor and if you need more power up the gearing or voltage.  Its great having all of the choices we have these days as far as electronics.  The longer can motors are nice because you usually have more leeway as far as gearing/voltage before they start getting hot.  

If you really want to stay with 2S then a higher kv brushless system is the way to go, but I would really recommend trying to set the truck up for 3S as it will give you some more options.  3S hard packs are pretty cheap these days, I've recenty starting running a lot of my vehicles on 3S and as long as you drive them sensibly it works out well.

[Mad Ax]

Awesome, I knew I'd get some great answers here  

I love the 1080 ESCs and I think I might even have a spare one somewhere, and I might even have a Traxxas 550 lying around.  Failing that I'm sure I've got an older HPI 550.  That means I can get the truck up and running with parts I already have, or parts that won't cost a lot to buy, and that's great because I can hopefully enjoy a nice build over the Christmas holidays instead of having to wait until next year

I've got some great ideas for the body too but I'll keep those quiet until I start a build thread

[87lc2]

Cant wait to see what you do with it.  The SMT10 is such a good looking scale truck I love seeing what others do with them.  Definitley get it up and running with what you have.  Start with the stock 14/56 gearing and go from there.  Even small pinion gearing changes make a big difference on this truck, so if the motor is running cool at whatever voltage you want to run go up a tooth at a time until you find where you want to be.  The HW 1080 is a gerat ESC for this truck as well when using brushed motors, can't go wrong there.

The biggest thing with the SMT10 (and solid axle trucks in general) that people dont realize is that you can't drive them like an Emaxx.  I know you're well versed in solid axle so it's not news to you, but if you drive it like a solid axle truck is meant to be driven they are a lot of fun and can be durable at reasonabl power levels. Even in my higher powered trucks I drive them like real monsters; set up a few ramps and make sure the truck is lined up straight and go for it.  One-wheel landings under power are a sure-fire way to hurt the truck, just like a real one...

[Mad Ax]

Yes, I'm really excited about getting it built.  I've got a couple of solid axle monsters but I'm not really well-versed in how to drive them as we don't do racing over here and I haven't really got a good place to bash them.  I had some fun trying to get Durandal to jump straight but it was before I'd sorted the spring rate and caster angle issue and it took more than a few attempts to get it to go off the end of the ramp and not off the side.  I'd spend more time in the garden playing around but realistically the only free daylight I have this time of year is a Sunday when I'm either taking the opportunity to be somewhere other than home (lockdowns and weather allowing) or I'm in the workshop making the most of a long day to get some stuff built.  Sometimes I take my daughter out on a Saturday and sometimes she enjoys sitting and watching as I race around, but as more public entertainments get closed down and bouts of good weather get less frequent, there's more demand on the space I use for bashing and ultimately a solid axle monster is too big and clumsy to be using where people are parking and trying to enjoy the countryside.

A local friend was considering getting an MTX-1 or the new LMT, if he goes that route we might be able to set up a small course in the fields, I could even bring my TXT-1 and mod clod (if I ever get it rebuilt) and invite a few other non-RC mates along (assuming the Rule of 6 doesn't become a Rule of 2) for a spot of light-hearted competition.  It doesn't seem worth dragging the ramps and cones all the way to the fields just for one.

[87lc2]

I definitely unerstand the free time thing this time of year.  Any free time I get I'd rather finish up some projects rather than running trucks, but I do miss running them more often.  They are definitely more fun with others, but I enjoy them on my own as well.  I like to set up mock courses similar to what the 1:1 courses looked like in the late 80s/early 90s and just do quick heats to improve my driving.  It does help that I have a massive backyard with plenty of room. 

Driving solid axle trucks is definitely a challenge and very different than an independent supsension rigs, I really enjoy them.  I have always had a passion for 1:1 monsters (grew up going to a lot of shows with my father), and I can appreciate the RC versions acting like the real thing.  Other people, even RC friends, don't get them and think they're too slow or break too often.  They're not wrong, I often break parts even when running by myself and being careful but that's just how it is.  I think you really need to appreciate these trucks for what they are rather than trying to make them "bulletproof" or into a Traxxas type rig as far as performance/durability, that's just not going to happen.  I am excited to get the LMT (preordered the roller last week), but I'll still treat it as any other solid axle truck even though from the videos I've seen online it looks like they can take a lot of abuse.  

[Mad Ax]

By British standards my garden is fairly big - 5m by 15m - and it's an even mix of patio and turf, fine for 2.2 buggy wheels and up.  The downside is that it's dotted with climbing frames and heavy garden furniture, which are all really bad for bashing near.  The main straight on my rallycross layout is patio surface, 10 metres long, 1 metre wide and is bordered with solid upright fence posts every 2 metres, which are just guaranteed to take the corner off anything that hits them at full chat.  This year my garden breakages have been nil but that's because I've been driving small cars carefully.  The 2.2 TLT-based rig is about right (I still need to finish the battery mount) but the TXT can be a handful.

I love 1:1 monsters too, and always have, even though they're rare over here.  A few years back I saw two full-size trucks doing a demo at a local Truckfest.  The noise was incredible and it was fun to see them racing around the arena, but all they did was crush a few old cars - there were no wheelies or jumps or anything like that, I suppose there wasn't enough space or crash protection as it was taking place in an agricultural showground, not a super-size sports arena.  I love the idea of being able to drive my rigs in the same way - I guess I'll have to dig out those broken touring car bodies and line them up on the lawn

Earlier this year I did a promo vid of the TLT rig jumping off a ramp for a works thing, I lined up some of my favourite vintage runners under the ramp - once I'd worked out just how far the truck would reliably jump, of course  

[Saito2]

Glad to see the SMT10 getting some love here. I'm just finishing up the chassis on my kit. It went together pretty nice overall. The reinforced plastics were a nice break form the shiny Tamiya stuff. I have a Castle Sidewinder 4600 V2 that been on my bench for years but I think I'll start with a Traxxas 12T 550 Titan I've also got laying around. Current plans are to run Jconcepts Rangers on Midwest rims, but those Duratrax Munition tires look cool. I don't think I'll step away from 2.2s though. Looking at how compact the transmission is compared to a TXT makes me think twice about huge tires even though the axles appear to be the weal link now. I built it stock, looked at it for 30 seconds, decided it was too long, and ordered 12.5" wb CPE  links this morning.

[87lc2]

The truck is very long stock..13.9" I think.  With the right body it can look OK though and is nice and stable.  My only stock length truck is the Thunder Chicken using the JConcepts 88 Chevy Snoop Nose body and it looks pretty good.  All of my others are around 13", I think that's the perfet wheelbase for these.  The 12.5" works great too, very popular upgrde for these trucks. 

You're correct on the TXT transmission being able to handle a lot more power, it's not even close even with plastic gears in the TXT trans.  I run the Castle (V3 I think?) SW with 4600kv motor in the Chicken and it goes pretty good.  However @Bash & @OldSchoolRC1 are spot on when saying a 550 motor works best in these trucks.  I only run the 540 size in race trucks as they tend to get hot when bashing for more than 5 minutes or so.  The 12T Titan will be nice, just gear her up if you want more speed   

[87lc2]

Also - if you're putting an aftermarket body on the SMT, make sure to install the exhaust headers on the opposite side of the chassis so they face down.  The really only work facing up with the Digger body.  Telling you this because they're a pain to get to once the chassis is fully assembled...

[Saito2]

1 hour ago, 87lc2 said:

My only stock length truck is the Thunder Chicken using the JConcepts 88 Chevy Snoop Nose body and it looks pretty good. 

And that Thunder Chicken of yours looks great. I was even considering the Snoop Nose body too with the stock wheelbase but I gave up on account of the 2.2 tires I'll be sticking with. I felt the larger tires were the key to getting the stock wheelbase to look right.

1 hour ago, 87lc2 said:

Telling you this because they're a pain to get to once the chassis is fully assembled...

Yeah, I just looked at those and that looks like no fun. Hopefully when I tear the suspension apart after Christmas to put the new links in, they will be easier to access. I still haven't decided on a body or scheme yet. I have some Taurus decals but they might go on my tuned up TXT2. I dunno. If I do a Taurus, do I have to crush King Yellows? (One of the 1:1 Taurus's claim to fame was crushing school buses).

[Dakratfink]

I have an Onyx 70A 2-3S 3000kv setup in mine. On 2s I’m wanting a little more. I’m gonna put axle tubes in and try it on 3s in the  The spring

[87lc2]

2 hours ago, Saito2 said:

And that Thunder Chicken of yours looks great. I was even considering the Snoop Nose body too with the stock wheelbase but I gave up on account of the 2.2 tires I'll be sticking with. I felt the larger tires were the key to getting the stock wheelbase to look right.

Yeah, I just looked at those and that looks like no fun. Hopefully when I tear the suspension apart after Christmas to put the new links in, they will be easier to access. I still haven't decided on a body or scheme yet. I have some Taurus decals but they might go on my tuned up TXT2. I dunno. If I do a Taurus, do I have to crush King Yellows? (One of the 1:1 Taurus's claim to fame was crushing school buses).

You're absolutely right, if sticking with 2.2 wheel/tires the stock wheelbase is waaay too long no matter which body you fit.  12.5" will be perfect.  On my 2.2 SMT10 I'm using the JConcepts 79 Ford crawler body (12.3" wheelbase).  I like that their crawler bodies are a bit wider too, 8" as opposed to 7" for the monster truck bodies.  Maybe look into some of them, there are some nice ones.  They have a 70 C10, 82 GMC, and a few others.

Good call on crushing King Yellows with Taurus, I remember seeing that on TV (or a video, cant remember) when I was a younger.  I was positive he was going off the right side of that bus, good thing he kept it on there.  If I remember correctly that truck was destroyed after that appearance being in an accident on the highway.  Taurus was always a great looking truck, love that scarlet red/yellow color scheme.