540 vs 380 in RM-01

[Kingfisher]

Currently building my RM-01. I've opted to not use the 380 motor that came with it and installed a 540 silver can instead. I've never ran a 380 motor, so I am wondering what the power difference will be if I were to use the little 380. The kit comes with a 14T pinion. Will this cause excessive wheel spin with the 540, or should I go with a bigger pinion for more top speed?

[Yalson]

Not sure what cars the RM-01 chassis relates to, but BiTD when I first got my Grasshopper 1 – complete with 380 and non-removable brass pinion – one charge of a 7.2v 1200mah humpback battery pack used to last around half an hour, depending on terrain. By contrast, when I installed a 540 and the slightly larger pinion which went with it (the only one which would fit, due to the fixed motor mounting points), it lasted for slightly less than ten minutes. Not a scientific experiment, I know, but hopefully indicative of relative performance.

My suggestion would be that unless you have to have absolute authenticity (or are building it for a small child), I would dump the 380 straight away and replace it with something a little more spritely, because they really are weak as water.

[Kingfisher]

Thanks. I am building this one.

 

[Yalson]

Yeah, you'll probably want to upgrade to a 540-size motor on that, because unless you're building a shelf queen the performance from the 380 is going to be hugely underwhelming.

[speedy_w_beans]

You might try the 380 first to see if you like it.  The RM01 is a very light car, and the last time I looked at the Mabuchi spec sheets I think the 380 actually achieved a higher RPM.  It just has less torque, which would make a difference in heavier models.  The name of the game is minimum weight for pan cars.  It's included in the kit and therefore free, so trying both doesn't hurt.

[qatmix]

If you are not racing then the 380 is fun enough. I have a RM01X that I run with 13.5 brushless and 1S lipo and it’s good fun but still quite smooth and slow for racing.

[nowinaminute]

I would generally go with a 540 given the choice, more powerful and under-stressed in comparison.

The 380 Tamiya supply usually has a similar no load RPM to the 540 but you are supposed to use a smaller pinion to make up for the lack of torque. For example, with a Grasshopper, the initial acceleration isn't that much different between the 380 and a silver can but because of the gearing the car will very quickly hit a brick wall when it comes to max speed. If it was geared faster the motor would just burn out, it already gets pretty toasty with the stock gearing.

The positives of using the 380 in the hopper is that it's one of the few powerplants that the chassis can comfortably handle no matter how relentlessly you drive it and you get great battery life too.

With a chassis like the RM-01 which actually likes going around corners quickly, I'd definitely go for the 540 unless you wanted the extra run time.

[Kingfisher]

Thanks. I have a few batteries, so run time isn't that big of a deal. I'll try @speedy_w_beans ' suggestion and try both. I like a faster car, so the 540 with a bigger pinion may be the way to go. Only one way to truly find out and that's to finish building it. 

[nowinaminute]

22 minutes ago, Kingfisher said:

Thanks. I have a few batteries, so run time isn't that big of a deal. I'll try @speedy_w_beans ' suggestion and try both. I like a faster car, so the 540 with a bigger pinion may be the way to go. Only one way to truly find out and that's to finish building it. 

See how you get on, yeah!

You never know, you might like the novelty of having a smaller motor and how it might effect your driving style. I suppose you could gear it up to a degree as long as you were careful not to accelerate too hard, try and go fast by conserving speed like some of those races you get with vehicles designed to be as fuel efficient as possible.

With the recommended gearing it will probably accelerate fine, it will just lack top end speed. I never had hobby grade as a kid and only got back into RC a few years ago. One of the first kits I built was a rere Grasshopper and when I tried it in my living room I thought "blimey that's faster than I expected" but then when you take it outside you realise that if your living room was about 30cm longer it would have maxed out lol

I haven't honestly got any direct experience with your chassis, only a Grasshopper and DT-02 so I can't make a true comparison but those two platforms are still perfectly fun to drive with a 380, they have plenty of low end grunt for rooster tails etc and sometimes it's nice to have a setup where the chassis is so underutilised that you can pretty much drive as recklessly as you like and it won't flip over, very handy for younger drivers too!

I think Kumamon breathes a sigh of relief about his 380 under the hood every time my daughter picks up the controller.

[wolfdogstinkus]

Can I have a look at your pinion?, 

Too late now as I mashed the gearbox but for future reference, it might be helpful. I wonder if it's interchangeable with a different model?

I had a 380 in the Sand Rover, it's nippy but gets boring quick, try it first, then go brushless.  

[nowinaminute]

 

2 minutes ago, wolfdogstinkus said:

I had a 380 in the Sand Rover, it's nippy but gets boring quick, try it first, then go brushless.  

Same with my Kumamon Sand Rover, I keep the 380 in because it's my daughters. It's great off the mark but the more open the space you use it in the slower it seems lol. Get it in a car park and it feels like you're waiting 5 minutes for it to get from one side to the other.