Motor selection help for big, heavy, slow 6x6

[Itali83]

I'm going to be building a scratch built big rig at some point. Going to be making everything I can from scratch so I'll have room within reason to put a big motor in this. I'd like to keep the motor able to bolt up to my vaterra ascender transmission but may look into a forward motor mount and run the transmission as just a transfer case which will give me more options on motors I think.

I'm newish but have a handle on 540 motor terminology and what turns means etc. I'm staying brushed. No brushless systems in this truck. I just want a big motor with tons of power for the truck. Truck is going to be 20lbs or more and hauling around my 8-12lbs scalers. I like how Rc4wd has the sealed can 540's in just about every turn you'd want. I don't see 550's like that. Maybe because I'm still a newb?

So I'm looking for advice basically on bigger more powerful motors than the typical 540. Want to be budget minded. Dreaded words I know but I want to keep the cost down on things. Let me know what you guys know and have used. Thanks!
Ben

 

[JatoTheRipper]

RC4WD motors work fine in light rigs. I have used them. For a heavy rig I would suggest investing in a good motor like Brood or Holmes. They are both vendors on here. Brood (EddieO) is very responsive to PMs.

 

[mikemcE]

Holmes Puller Pro XL
No not brushed, you really want a brushless motor the weight will help accelerate brush and comm wear


Hang up and Drive

 

[Jeepy84]

Holmes Trailmaster Sport 550s make more power and bolt up just like a 540. Traxxas Titans also. I do believe however I haven't seen any with more or less than 21 turns.

Sent from my XT1585 using Tapatalk

 

[svt923]

The biggest brushed motor I have used is a 550 which would bolt up to the Ascender transmission no problem. Not sure if that would live a long life in a 20 lb truck without a lot of gear reduction. The largest brushed motor that fits a 540 sized mounting plate is a 650 sized can if my memory serves correctly (the info on this stuff is mostly from the early 2000's in the Traxxas monster truck heyday). Larger motors like the 700 cans start having different mounting bolt spacings. Kershaw Designs sells a 650 motor but you can likely source a generic Mabuchi version for much less (like this 1Pcs MABUCHI RS-650S DC20.4V High-speed Motor Car Model Aircraft Motor | eBay). Whatever motor you go with, volt up and gear down.

Here is a old pic for a visual reference on brushed motor sizes

 

[Rjohn929]

6s on a roc 412hd 500kv.

 

[Itali83]

I still want to stay away from brushless for cost reasons. I've been looking at some eBay motors but am worried because they all say high speed motors. Don't give turn count. I'd like to get a high turn count motor and put the volts to it. I'm really leaning towards remote motor mount so fitting where a 540 can would isn't a problem.

I've seen the Holmes hobbies trailmaster 550's but the turn count seems low compared to what I run with my 540's. I like motor sport in the 55turn area. But I'm going to gear this down even more than just the single transmission so it may work out fine with a faster motor. Thanks again guys!
Ben

 

[svt923]

I've seen the Holmes hobbies trailmaster 550's but the turn count seems low compared to what I run with my 540's. I like motor sport in the 55turn area. But I'm going to gear this down even more than just the single transmission so it may work out fine with a faster motor. Thanks again guys!
Ben

The bigger the motor, the less turns it takes to get similar RPMs. A 21T 550 motor is roughly equivalent to a 27T 540. From my best understanding it has to do with the longer armature makes each wind longer so you get the same amount of copper fill from less turns. I'm sure JRH or EddieO could explain it in an amount of detail that will be lost on 90% of us.

 

[Rjohn929]

You talking a full custom build moving 30-40lbs of weight. Your going to need a quality motor. Sealed can cheap motors or eBay crap is not going to help you. Reference Szczerba's build #58. You get what you pay for, especially for electronics. Will the other motors work, sure.... for about 3 minutes.

 

[magic_yeti]

30 lbs is the rating of the castle 2028 extreme which is meant for 1/5 Scale:shock:.
I think every 540 550 Motor is to weak for such an heavy rig. :twisted:

My solution would be make the rig lighter or maybe plan it with more than one motor.

Hope to see the build thread if u start."thumbsup"

 

[Itali83]

Thanks guys. Kinda had my Hearn up my butt on this one. I followed szerzba's build and never paid attention to his power plant. Off to the multi axle forum I go. Thanks guys!
Ben

 

[Natedog]

The biggest brushed motor I have used is a 550 which would bolt up to the Ascender transmission no problem. Not sure if that would live a long life in a 20 lb truck without a lot of gear reduction. The largest brushed motor that fits a 540 sized mounting plate is a 650 sized can if my memory serves correctly (the info on this stuff is mostly from the early 2000's in the Traxxas monster truck heyday). Larger motors like the 700 cans start having different mounting bolt spacings. Kershaw Designs sells a 650 motor but you can likely source a generic Mabuchi version for much less (like this 1Pcs MABUCHI RS-650S DC20.4V High-speed Motor Car Model Aircraft Motor | eBay). Whatever motor you go with, volt up and gear down.

Great advice/info! Kyosho Magnetic Mayhem, awesome motors but not enough for this project. "thumbsup"

Your going to need a quality motor. Sealed can cheap motors or eBay crap is not going to help you. Reference Szczerba's build #58. You get what you pay for, especially for electronics. Will the other motors work, sure.... for about 3 minutes.

"thumbsup"

 

[Jeepy84]

I too was thinking you will spend more in motor replacement than just going brushless out the gate after everyone else reminded me of the kind of weight you're looking to move.

Sent from my XT1585 using Tapatalk

 

[durok]

Kershaw is definitely a blast from the past, but they are still around - with some options for heavy rigs:

Kershaw Designs - Home

 

[snapon boy]

As a 6x6 builder/owner,i use a brushless 13.5t Holmes hobbies trail master and I have pulled my kid in the wagon more than ones or pushed my kids Trycycle up the hill and it dose fine on 3s. However mine is probably 10 lbs at most

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[E. Bryant]

The bigger the motor, the less turns it takes to get similar RPMs. A 21T 550 motor is roughly equivalent to a 27T 540. From my best understanding it has to do with the longer armature makes each wind longer so you get the same amount of copper fill from less turns. I'm sure JRH or EddieO could explain it in an amount of detail that will be lost on 90% of us.

It's a matter of total magnetic flux in the motor assembly; as the motor gets longer, there is a greater surface area of armature exposed to flux, and thus one needs fewer turns to generate the same back EMF. And since you have fewer turns, you potentially have less resistance, so you can pass the same current with less heat. Combine this with the fact that the motor exterior surface area is greater, and you've got a motor that can generate the same power with less temperature rise, which is generally a good thing.

I'm a big fan of putting bigger motors into bigger models if space allows. I'd think that a 550 can would be a good starting point, but I might explore one of the Mabuchi 775 options. Depending upon the model's weight, desired performance, and battery voltage, there might be a good cheap option from the power-tool world.