Typical Crawler top speed

[Jmsideshow]

I'm in the process of building my first crawler and I'm having a little trouble deciding on a motor. Everyone here seems to be running super high turn motors on 3S to 6S packs. The problem I'm encountering is none of these motors have a kva spec listed anywhere in the known universe. Just how fast will one of these infinite turn motors spin when you juice them with 1vdc and just how fast will the average crawler top out at?

My current plan is a 40:1 custom tranny with a 725kva motor and a 6S lipo. When I set it up with a set of ROK LOK 4.0 tires I get a top speed of about 11mph. Is this in the ballpark or am I playing the wrong sport?

Any help or ideas anyone an offer will be greatly appreciated.

 

[chase1deer]

question

good ?? wondering the same thing,,put the same motor in 2 identical creepers, and the speeds were totally different,,

 

[Charlie-III]

Brushed motors do NOT have KV ratings, but:

27turn ~= to 17.5 (or 2200KV)

Brushless (BR or BRL) motors DO have KV ratings.

A 13.5 BR ~= 3300KV

Most Crawlers use low KV/high turns motors so you get the torque within gearing limitations and desired wheelspeed. This is a lot different than a road course/dirt course RC car or truck which are looking for higher wheel/vehicle speed.

Hope this helps some.8)

 

[Charlie-III]

good ?? wondering the same thing,,put the same motor in 2 identical creepers, and the speeds were totally different,,

If the motors, batteries & ESC's are the same, then either the pinion gearing is different, or there is more binding in the slower one (trans, gear mesh, bearing condition, etc.)
Maybe the transmitter setups were different??

 

[Jmsideshow]

Brushed motors do NOT have KV ratings, but:

27turn ~= to 17.5 (or 2200KV)

Brushless (BR or BRL) motors DO have KV ratings.

A 13.5 BR ~= 3300KV

Most Crawlers use low KV/high turns motors so you get the torque within gearing limitations and desired wheelspeed. This is a lot different than a road course/dirt course RC car or truck which are looking for higher wheel/vehicle speed.

Hope this helps some.8)

Well that sure explains the lack of kva ratings I guess :lmao:. Now, how about top speed? Can you out run your crawler or do you just have to power walk to get ahead of it? 10 mph sound too fast with a 6s pack?

 

[Charlie-III]

I'm running 35turn brushed (x2) on my Bully rig geared middle of the road. I would guess it tops out around 7MPH on a 3S LiPO pack?
It will go up a ~60* sandpaper covered board at a crawl, so it still has decent torque for climbing.

The sandpaper covered board thing is from the Venom Creeper forum, my son has one so we compared vertical crawling angles.:ror:

 

[08sv]

this may come in handy for you in the future, or i hope
FOR BRUSHLESS: This number is the motor voltage constant expressed in RPM/Volt. This indicates how fast the motor will turn for a given voltage (given there is no internal resistance). As an example, the SS5800's Kv rating is 5,800 RPM/Volt. Therefore, if a 6.0-volt battery pack is used, the SS5800's RPM would be 34,800 (6.0 x 5,800).
and here's a lil calculator if it helps out.
http://www.4lo.com/calc/gearratio.htm

 

[Jmsideshow]

this may come in handy for you in the future, or i hope
FOR BRUSHLESS: This number is the motor voltage constant expressed in RPM/Volt. This indicates how fast the motor will turn for a given voltage (given there is no internal resistance). As an example, the SS5800's Kv rating is 5,800 RPM/Volt. Therefore, if a 6.0-volt battery pack is used, the SS5800's RPM would be 34,800 (6.0 x 5,800).
and here's a lil calculator if it helps out.
http://www.4lo.com/calc/gearratio.htm

I understand the idea behind the kva rating, what I'm ultimate trying to figure out is how fast do most crawlers go flat out, fresh batteries, etc. I am just worried my rig will be too fast to be controllable in the rocks. The wrong set of motors will be an expensive mistake to make, and since I already bought them, I'm hoping I won't have to build a rock racer instead of a crawler.

 

[entropy]

The speed of a crawler, in my case, which has a gear reduction box, is faster than the speed of smell - well unless theres a good breeze:lmao:

 

[TrailDawg362]

My rig is running a 55 on 3S, reasonably geared and scoots along at a brisk walking/jogging pace when wide open.

 

[WIDELOAD]

im running i 1200kv brushless outrunner in my scale rigs geared 14/87 on 3s and its a brisk jog pace...

 

[Charlie-III]

I understand the idea behind the kva rating, what I'm ultimate trying to figure out is how fast do most crawlers go flat out, fresh batteries, etc. I am just worried my rig will be too fast to be controllable in the rocks. The wrong set of motors will be an expensive mistake to make, and since I already bought them, I'm hoping I won't have to build a rock racer instead of a crawler.

Since you're in NNJ (like me) all the rocks have 1'+ of snow on them.:evil:
You should have an idea on "dry land flat out speed" now, but on the rocks is the only way to know for sure.
If it's too fast, going smaller on the pinion gear and/or up on the spur gear can slow the rig down."thumbsup"

 

[Jmsideshow]

Yeah, at least a foot, though I've got closer to 5 feet in the front yard. The spur/pinion change is unfortunately irrelevant to my design since it is a worm drive gear and the motor drives the worm directly. If I want to change the ratio I have to redesign the entire transmission.... Again. I guess I'll take my chances with what ive got in the works, Ill just put on smaller tires if it's too fast. "thumbsup"

 

[Charlie-III]

Yeah, at least a foot, though I've got closer to 5 feet in the front yard. The spur/pinion change is unfortunately irrelevant to my design since it is a worm drive gear and the motor drives the worm directly. If I want to change the ratio I have to redesign the entire transmission.... Again. I guess I'll take my chances with what ive got in the works, Ill just put on smaller tires if it's too fast. "thumbsup"

OK, I understand the worm gear drive issue.

Join (or at least sign in) www.GSRCRC.com, some of us are "local" to you. We run events (mostly central NJ & eastern PA) but we're trying to get some NNJ peeps together for fun & tuning."thumbsup""thumbsup"

Tell them, "Charlie sent you!"......hahahahaha

 

[Charlie-III]

Stupid (but rather late....) question.....is this for fun, scale comps or 1.9/2.2 comps????:roll:

Regardless, this site, as well as GSRCRC, can help you out."thumbsup""thumbsup"

 

[Jmsideshow]

Stupid (but rather late....) question.....is this for fun, scale comps or 1.9/2.2 comps????:roll:

Regardless, this site, as well as GSRCRC, can help you out."thumbsup""thumbsup"

Fun/Super competition from time to time if I can keep it shiny side up during the fun time anyway.

I gave up and did a redesign of the transmission anyway. It incorporates a Robinson racing spur/pinion combo now for a ratio range of 20:1 to 80-ish:1. Hope that's enough spread to get the speed I need. :lmao:

I'll defiantly check the site out I'll need all the help I can get when the time comes to get her on the rocks.