When you can no longer gear down, when you hit the voltage limits of the hardware, or when you hit the rpm limits of the motor.
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Hobbywing Xerun AXE
- Thread starter Jboucher
- Start date
When you can no longer gear down, when you hit the voltage limits of the hardware, or when you hit the rpm limits of the motor.
robert@castle
Quarry Creeper
Brushless motors have a minimum RPM that they will spin smoothly. We tested some 2 pole motors and most of them were 600-800RPM depending on the brand and the wind. On our slates we were able to get to spin smoothly at around 100-150RPM on V2.02. Minimum RPM doesn't change much with voltage as long as the ESC has enough PWM range and throttle resolution to handle the higher voltage.
Even with a slower spinning motor, the more you gear down the slower the truck will run with that minimum RPM. So really following Holmes' advice could actually make your truck run slower, but then give your more power when you want/need wheel speed. There really is no downsides to Volt up Gear down besides having to buy higher voltage batteries.
Good stuff! "thumbsup"
So typically I run a 35T brushed motor. Would I have to choose a different turn motor on 4S?
Same goes for brushless. My Bomber has a 3500kv Puller Pro. It's already too fast for my liking, but I have yet to change gearing. Would I have to go with a lower kv on 4S to maintain the same speed? Eventually you'll run out of gearing choices.
3500kv on 3s with stock 12T is about 21.51mph
3500kv on 3s with a 10T is about 17.92mph
2700kv on 4s with a 10T is about 17.94mph
I think the bomber is able to go down to 9T and you can up the spur to 68T.
Plus all the EXPO from rhe radio and throttle curves from the ESC...
But we are getting off-topic from the Xerun AXE...
3500kv on 3s with a 10T is about 17.92mph
2700kv on 4s with a 10T is about 17.94mph
I think the bomber is able to go down to 9T and you can up the spur to 68T.
Plus all the EXPO from rhe radio and throttle curves from the ESC...
But we are getting off-topic from the Xerun AXE...
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Robert hits a great point in great terms. The startup speed of a motor does not change when voltage changes, so by gearing down a truck and using higher voltage you can gain slower startups as long as the controller has the PWM range and throttle resolution.
35t will run 4s no problem. At least mine do.
In regards to the 3500 Puller, there really isn't a need to run 4s. But 3s is certainly better than 2s. As you say, there is a point where you can't gear down any more. Run 3s, gear that sucker down since you have more than needed wheelspeed, and go from there. If you geared down and then needed more wheelspeed back, it's a perfect time to add more voltage.
35t will run 4s no problem. At least mine do.
In regards to the 3500 Puller, there really isn't a need to run 4s. But 3s is certainly better than 2s. As you say, there is a point where you can't gear down any more. Run 3s, gear that sucker down since you have more than needed wheelspeed, and go from there. If you geared down and then needed more wheelspeed back, it's a perfect time to add more voltage.
So 2700kv 4s geared down to 10/68 would make more sense in a crawl / trail rig and the 3500kv 3s on stock ratio is for rock racing / U4 right?
Sent from my Nexus 6 using Tapatalk
Sent from my Nexus 6 using Tapatalk
more or less. It's always a balance of needs though. A 3500 on 3s geared down would probably have a lower center of gravity due to battery height. A 2700 on 4s geared down would have a cooler running ESC and battery, if it was being pushed hard enough. Performance wise (assuming the ESC and battery can handle the amp draw without issue), the two systems would be nearly identical in performance since the motor spins about the same speed.
A lot of U4 racers are even running the 3500 on 4s now. Then we would be comparing to a 2700 on 5s, which would present a problem of battery fitment in the rig. Hence why many U4 racers stop at 4s and then choose the KV based on that voltage.
A lot of U4 racers are even running the 3500 on 4s now. Then we would be comparing to a 2700 on 5s, which would present a problem of battery fitment in the rig. Hence why many U4 racers stop at 4s and then choose the KV based on that voltage.
I picked up a couple 4S packs to use in my HH Revolver 1800kv build, and the 4100kv HH Puller Pro 540-L "R" motor will get 3S power, with under-driven axles front and rear.
The 4100kv is rated at a higher RPM level than the lower-kv Puller Pros, 60,000 instead of 50,000.
Should be fun!
The 4100kv is rated at a higher RPM level than the lower-kv Puller Pros, 60,000 instead of 50,000.
Should be fun!
It's about time someone brought out a new sensor wire standard. Never understood how a fragile plug from an early 80s computers became tolerated or worse, accepted. I hope HW put this on a public license, free to use so it can become the new standard.
magic_yeti
RCC Addict
The HH Puller Pro 540-L "R" motor is definatly fun "thumbsup", i use it in my little monster:mrgreen: on 3s with a mmx. But be aware of breakages
First Test Drive ended after 30min with a 2WD yeti8)
but back to topic ;-)
i think hw gives us a new option with some good ideas. especially the sensor wire"thumbsup"
And they rate esc and motor ip67:mrgreen: i may give it a try for my trex, but i would like a 2800kv - 3000kv option hopefully they will release this option in the near future.
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I don't think this plug will become standard, but I do agree we need a new standard. The current sensor cable is, to put it bluntly, fragile and unreliable garbage.
I certainly agree with sensor ports being terrible. I'm not a fan of hard wires coming out of the case with a plug in the middle, but at least they are trying something different. I've also been working on a new standard. The last decision is between a 6x1 or 3x2 plug body.
MasteroFlego
Rock Crawler
I'd also go with 3x2. What would make you consider the 6x1 instead?
More polarized options, easier to fit on the back of a motor without interfering with bearing or edge of the case.
Ah makes sense.
Is that with a motor included?
At that price, why not just get a Mamba X with a crawler motor?
