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Old 11-03-2019, 04:51 PM   #1
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Default 4S and low gearing to get good crawling and speed?

I know there's a ton of info here and elsewhere and i've spent quite a bit of time searching and reading but still haven't been able to piece together a clear answer to this question.

Is 4S and low gearing with a brushed motor a good way to get slow speed crawling torque and smoothness and still have a pretty quick top end?

I recently picked up a used wraith with a 550 traxxas titan 21T motor (I was told it's 21T anyway, it doesn't seem to indicate that on the motor anywhere). I read on traxxas forums that these motors can be used on 4S.

The motor is getting SUPER hot when crawling right now on 3S (and it's also not very strong, "stalls" a lot) in my wraith with 80/20 gearing, 87 tooth spur is in the mail and then i'll be trying 87/16. That should help cool things down and help with crawling, but I'll be sad to give up the speed. It's not really very fast as is on 3S lipo. It's slow/weak as hell on 6S nimh.

I hear gear down and volt up, that sounds like a great idea, but then i hear that 4S tends to cook commutators and brushes on some motors (not others?). What makes a motor able to take higher voltage, and what are the drawbacks to that motor?
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Old 11-03-2019, 10:10 PM   #2
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Default Re: 4S and low gearing to get good crawling and speed?

Sounds like the motor is shot....

3s on a 21 turn motor will be very fast for a crawler. not a bad thing imo.... 4s is usually reserved for brushless motors.
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Old 11-03-2019, 10:34 PM   #3
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Default Re: 4S and low gearing to get good crawling and speed?

I run 4s brushed on my moa, sporty and class 2. You'll want to go a lot lower than 87/16 with that motor.
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Old 11-04-2019, 03:11 AM   #4
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Default Re: 4S and low gearing to get good crawling and speed?

It's hard to get decent speed for bashing and jumps, while still being able to crawl well on a brushed motor. That's a big reason why people go brushless.

Your heat is probably due to trying to crawl with those high gears. Even 86/16 is high for crawling. 86/10 or 11 maybee. But then you're not going to be jumping much.

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Old 11-04-2019, 03:13 AM   #5
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Default Re: 4S and low gearing to get good crawling and speed?

When your motor stalls out you're basically turning all the power you're throwing at the motor into heat.

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Old 11-04-2019, 09:29 AM   #6
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Default Re: 4S and low gearing to get good crawling and speed?

Quote:
Originally Posted by Voodoobrew View Post
86/10 or 11 maybee. But then you're not going to be jumping much.
Ok, that makes sense. That's why i'm asking about 4S. If i went to 87/11 i'd have good crawling but low top speed. Would 4S bring back the top speed while retaining the crawling?


Quote:
Originally Posted by Voodoobrew View Post
When your motor stalls out you're basically turning all the power you're throwing at the motor into heat.

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That's what i suspected, thanks for confirming.
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Old 11-04-2019, 09:33 AM   #7
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Default Re: 4S and low gearing to get good crawling and speed?

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Originally Posted by lonleycreeper View Post
Sounds like the motor is shot....

3s on a 21 turn motor will be very fast for a crawler. not a bad thing imo.... 4s is usually reserved for brushless motors.
21T in a 550 is different (slower but stronger) than in a 540 right? It is faster than my old honcho SCX10 all stock, although it stalls out a lot easier.


I wonder about the motor being shot/worn out. It still works, just seems slower than I might have expected. How can I tell if it's not performing as well as it should, is there something to visually inspect? I don't have similar rigs to compare to. I suppose i could swap the motor from my TRX4, i think it's the same thing, a 550 can 21T Titan.
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Old 11-04-2019, 11:16 AM   #8
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Default Re: 4S and low gearing to get good crawling and speed?

80/20 on 3s will be faster then 87/11 on 4s. If you used 80/15 on 4s it should be the same speed.

Basically just keep lowering gears till the motor runs cool enough to not burn up.


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Old 11-04-2019, 10:26 PM   #9
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Default Re: 4S and low gearing to get good crawling and speed?

Sorry, but i feel like i'm not getting a clear answer, or not understanding.

If i go 4S with low gears, will that give me a wider useable range of speeds?

Or, put differently: If i gear for crawling on 3S, then run 4S, will i have the same crawling ability but with improved top speed? Enough faster to bother with? Any drawbacks?

Thanks
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Old 11-05-2019, 05:18 PM   #10
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Default Re: 4S and low gearing to get good crawling and speed?

Higher voltage gives the motor the same low end, plus more max rmp.

Reducing gearing will increase the torque to the wheels, increasing low end drivability. This also reduces motor heat by reducing physical resistance to the rotation of the motor.

Reguardless of this if your motor gets hot from crawling you need to reduce the gear ratio or check that the drive train turns freely and fix issues there if it dosent or risk burning up the motor.


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Old 11-06-2019, 07:43 AM   #11
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Default Re: 4S and low gearing to get good crawling and speed?

Cool, thanks. So why doesn't everyone run 4s, or 5s for that matter? Why does anyone run 2s?
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Old 11-06-2019, 08:31 AM   #12
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Default Re: 4S and low gearing to get good crawling and speed?

Quote:
Originally Posted by TroySmith80 View Post
Cool, thanks. So why doesn't everyone run 4s, or 5s for that matter? Why does anyone run 2s?
Most run 2s because they just don't know any better. I didn't own any 2s until this last year, I started on 3s and moved to 4s. I was given 2s packs so I use them in my rental truck or wire them in series to make 4s.
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Old 11-06-2019, 07:14 PM   #13
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Default Re: 4S and low gearing to get good crawling and speed?

5 is a bit much for brushed motors. The brushes wear out too fast. The electrical arc explodes little bits of the brush material away.

6s on a brushless motor is a diffrent story though. It can explode your drive train...

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Old 11-08-2019, 04:05 AM   #14
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Default Re: 4S and low gearing to get good crawling and speed?

2s packs have worked fine for my needs. They are cheaper, still give me faster then I can walk while trailing speed, and my motors stay cool. I have played around with 3 and 4 cell and have worked fine, but it didn't change where I could go with my rig. If I made it on a 3s then I could make the same route on a 2s.
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Old 11-08-2019, 06:51 PM   #15
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Default Re: 4S and low gearing to get good crawling and speed?

yeah, i had an scx10 honcho and i have a trx4, with either of those, i have no desire to go faster than 6 cell nimh will take me. The wraith does considerably better at speed though so it's a little different story. If i gear it low enough to be a great crawler, it doesn't go as fast as i'd like it to, even on 3S.
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Old 11-09-2019, 03:52 AM   #16
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Default Re: 4S and low gearing to get good crawling and speed?

You make it sound like if the voltage gets higher I must be going faster. Voltage is only one part of a milti-part equation. My scx10 2 is geared down to 100:1 with a crawlmaster 550 10t. On 4s it's slower then a stock rig on 2s. But it will creep through anything at a snails pace without hesitating or lurching when it encounters obsticles because of the massive torque it produces.

This is why so many people love the revolver motors. The massive torque they put out. Gearing down so low and increasing the voltage means I don't need to listen to the high pitched wine of the revolver to get similar torque.

No disrespect but unless you have driven a rig like it, it may be hard to understand. But 2s is incredibly unlikely to match the feel. When the stock gearing and motor would bind up in jagged terrain it would drive me nuts. Volt up and gear down is the way past that issue.

There is a trade off though. You may get better battery life with 2s.

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Old 11-09-2019, 03:49 PM   #17
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Default Re: 4S and low gearing to get good crawling and speed?

@Voodoo and Whiskey-Tango...
Would you point me to a thrifty-ish brushed ESC that’ll handle 4S? After a thousand threads read, I’m seeing a cheaper option looking like Holmes’s BRXL? This for a Capra or light Element Enduro and Expert 35T or 13T five slot motors...
I have to buy another ESC anyway and I keep thinking about what you guys have to say about 4S all through the forum.
Peace, Linc.
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Old 11-09-2019, 07:13 PM   #18
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Default Re: 4S and low gearing to get good crawling and speed?

The hobbywing 880 can do it. But it's designed for 2 motors and dosent include the programmer.

I haven't tried it yet but I'm pretty sure it's the same as the 1080 on 4s if you only attach 1 motor. If it works cut off the extra leads, if not return it. I think it only costs $33.

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Old 11-09-2019, 07:24 PM   #19
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Default Re: 4S and low gearing to get good crawling and speed?

I've ran brxl, br-mini, fxr (with 4s capacitor) etc on 4s. For a wraith I'd say a brxl older mamba max pro if you can find it would be the better option. Smaller escs don't like heavier rigs for long before popping.
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Old 11-10-2019, 12:02 AM   #20
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Default Re: 4S and low gearing to get good crawling and speed?

I'm going 4s in my 1.9 Class 3ish custom build. I'll be using a BR-XL and a CM Pro 550 12T. Geared for crawling...probably around 8-10 mph top speed.
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