General kV and gearing question

[oldnick]

I’m planning on building a 1.9” Ali Express cheapo cheater over the winter.

No trailing, just crawling. 3s, ESCape32 esc, stubby out runner, trans to be decided, Capra axles, tyre size to be decided.

Given I crawl slowly and try to avoid rock bouncing what sort of kV and gearing should I be looking at?

1800kV seems middle of the road - any perks to going lower or higher?

Once that is decided how do you decide on gearing? I’ll be under driving the rear as much as possible, then adding overdrive to the front until it drives to my liking.

Ideally there would be a kV and gearing spreadsheet with target numbers for the style of driving, but if there is I’ve not found it!

Thanks in advance

 

[Col_Sanders]

On 3s I'd probably go for a 2200kv. That would also be good for 4s if you decide to do that later. There are final gear ratio calculators out there but I dont know if any are tailored to a driving style. Knowing what transmission you want to run would be helpful. Some offer more gearing options than others.

 

[svt923]

My general plan is to run as much gear reduction as practically possible and choose the motor with the KV to get to my desired wheelspeed at that gearing. When I plug my gearing info into a speed calculator, I like to see a top speed somewhere in the 6 MPH range for mixed use on my chosen voltage.

 

[ferp420]

in my opinion with outrunners you really want them geared low i like the 2200kv range with a 10t-12t pinion gear
i have a 1400kv with i think a 16t pinion and it works good too

the over/under is kinda funny for pure crawling you might be ok if your making alot of really tight turns or crawling small rocks like in a comp but for me the one rig i have set up like that i dont drive it since going over/under it hurts more than it helps and lesser rigs are walking circles around it and the motor gets crazy hot alittle over drive i think helps in some situations but not crawling in my opinion
i like the front and rear to have the same ratios for crawling it makes sence to have the front and rear working together instead of against each other

some people build rigs that work with heavy over/under they dial the suspension geometry in so the rig sucks down on to the rock but personaly ive never found that sweet spot

my advice would be start stock and try it then try under and then if ya like it and want more than do the front or go with a over/under drive transmission that lets you adjust the overdrive

 

[diezel666]

Ideally there would be a kV and gearing spreadsheet with target numbers for the style of driving, but if there is I’ve not found it!

And there-in lies the issue. Not only does Gearing and Driving style change a lot of things. So does the surface, and tires you run. The chart would be a mind numbing array and much of it may not matter to 75%+ of people.

Generally for crawling, depending on gearing and weight. 1800-2200kv is about what most people run.

On my rigs, I'm running the (sadly no longer available it looks like) Holmes Hobbies Revolver 540 SS 2023 Team Spec 2250KV.

 

[Col_Sanders]

And there-in lies the issue. Not only does Gearing and Driving style change a lot of things. So does the surface, and tires you run. The chart would be a mind numbing array and much of it may not matter to 75%+ of people.

Generally for crawling, depending on gearing and weight. 1800-2200kv is about what most people run.

On my rigs, I'm running the (sadly no longer available it looks like) Holmes Hobbies Revolver 540 SS 2023 Team Spec 2250KV.

I started the season with an 1800kv version of that motor in both of my trucks. Managed to snag one of the 2250s a few months ago and I'm glad I did. That extra bit of wheel speed is nice to have sometimes.

 

[89Industries]

Tire size also plays into this.

I make spreadsheets that calculate gear ratio then predicted top speed.

I just put together a new truck and it seemed slower than expected while testing it out. Realized I never changed the tire size from 4.75" to 4" in the spreadsheet. So now it makes more sense.