Limitless Speed Runners Motor KV selection

[Doom!]

While interesting, this stuff goes right over my head. I'm grateful for those of you that can make sense of it.

 

[LibertyMKiii]

@rotauq I have been anxious to see a back to back comparison with a Lehner motor vs a TP Power motor. The theory behind their motors sounds good, but I suspect they lack total power when the rubber/foam meets the road.

There has to be a reason besides price that no one is running those motors.

 

[rotauq]

@rotauq I have been anxious to see a back to back comparison with a Lehner motor vs a TP Power motor. The theory behind their motors sounds good, but I suspect they lack total power when the rubber/foam meets the road.

There has to be a reason besides price that no one is running those motors.

The idea of running without magnets gives this them a smaller form factor as a benefit. But the base principle of a brushless motor remains the same and doesn't make it behave any different then any other brushless motor.
I think it really is all about the price. Nothing else.

Then again, allied with MGM bounds them to the rare MGM customer. And those often are the ones that do a fantastic unboxing video, but never follow it up by impressive speedruns (at least not on surface)
I found one doing ~150mph:

In RC boats they do hold a 195mph record.

MGM/Lehner RTR limitless and limitless 8S ESC/Motor combo are still in preorder phase (says: preorder - available november 2020) so they are delayed. Maybe when these hit the market, we'll see more of them in action.

I like some of their Operating instructions though:

All motors are equipped with rotors optimized for partial power. This yields an efficiency loss of no more than 7% (typically 4 - 5%) at half power. If the operating parameters are outside the approved max. efficiency range (full power current too high), there is the risk of thermal destruction of the magnetic rotor through excessive eddy currents. You need to have allways an optimal adaptation.

There are many different motor controllers made by various manufacturers. Depending on design and software version they can behave differently (e.g. start, start protection, timing etc.). 7. Our rpm / power data have been determined by using 15° timing.

You could read it like, we don't perform very well on non-MGM controllers and currents go wild easily.

 

[LibertyMKiii]

The idea of running without magnets gives this them a smaller form factor as a benefit. But the base principle of a brushless motor remains the same and doesn't make it behave any different then any other brushless motor.
I think it really is all about the price. Nothing else.

Then again, allied with MGM bounds them to the rare MGM customer. And those often are the ones that do a fantastic unboxing video, but never follow it up by impressive speedruns (at least not on surface)
I found one doing ~150mph:

In RC boats they do hold a 195mph record.

MGM/Lehner RTR limitless and limitless 8S ESC/Motor combo are still in preorder phase (says: preorder - available november 2020) so they are delayed. Maybe when these hit the market, we'll see more of them in action.

I like some of their Operating instructions though:

All motors are equipped with rotors optimized for partial power. This yields an efficiency loss of no more than 7% (typically 4 - 5%) at half power. If the operating parameters are outside the approved max. efficiency range (full power current too high), there is the risk of thermal destruction of the magnetic rotor through excessive eddy currents. You need to have allways an optimal adaptation.

There are many different motor controllers made by various manufacturers. Depending on design and software version they can behave differently (e.g. start, start protection, timing etc.). 7. Our rpm / power data have been determined by using 15° timing.

You could read it like, we don't perform very well on non-MGM controllers and currents go wild easily.

I have seen a few Limitless with that MGM combo. None have ever posted videos or results...
A friend of mine runs FE boats says they work fine with other ESCs. Might be worth a try.

 

[rotauq]

Might be worth a try.

Maybe some day, right now i can't justify the high price

 

[LibertyMKiii]

The 1/5 scale motors are still a bit of a mystery for some of us related to results and what to expect. 40mm motors have been around for a long time so we have lots of data/results to look at.

A close friend has been developing his Infraction V2 for speed use and I thought I'd share some 1/5 scale motor results.
Motor - TP5680 1440kv D-wind.
LiPo - 6400mAh 6s SMV extreme V2
Speed: 127 mph on 6s

Amps were still under 400 (around 375 from memory) and the ESC only reached 90F. Motor was cool to the touch.
Voltage at the peak RPM was around 3.4v per cell (20.4v).

This was only his second run with the car. It appears this car could go into the 140s no problem on its current 6s setup and 150s on 8s!

 

[Fallguy]

New to speed runs. So a motor like the castle 2028 combined with a mmx8 would not be the best choice for 8s speed runs in a Limitless because of the low kv on the motor?

 

[rotauq]

New to speed runs. So a motor like the castle 2028 combined with a mmx8 would not be the best choice for 8s speed runs in a Limitless because of the low kv on the motor?

So you didn't read anything mentioned above?

2028 can give impressive speeds, you just need a huge pinion gear.

 

[LibertyMKiii]

New to speed runs. So a motor like the castle 2028 combined with a mmx8 would not be the best choice for 8s speed runs in a Limitless because of the low kv on the motor?

Read through the thread again as there is lots of good info here.
Innovation RC recently showed a Infraction/Limitless with GT body running 158 and 159mph using the XLX2 and 2028 (1100kv model)

 

[Fallguy]

So you didn't read anything mentioned above?

2028 can give impressive speeds, you just need a huge pinion gear.

I read everything. It's my first introduction to it. It's not the easiest stuff to understand. I have an opportunity to buy a combo with that motor so I thought I'd ask a question.

 

[LibertyMKiii]

I read everything. It's my first introduction to it. It's not the easiest stuff to understand. I have an opportunity to buy a combo with that motor so I thought I'd ask a question.

No worries, we all have to start somewhere. If you have the budget for it... that setup is killer with the 1100KV.
Ideally you will want the 2.8 diffs, which will help the lower RPMs of that motor. The sensored part is what allows it to take off so smoothly.

As a heads up you will need to beef up the drivetrain to handle that power. It would bend the stock dog bones like wet noodles!!!!

If I could afford the scorched titanium axles and spool setup along with this motor and ESC combo I'd probably keep my Limitless and speed run it more. As of right now that car is likely going to be sold soon.

 

[Fallguy]

No worries, we all have to start somewhere. If you have the budget for it... that setup is killer with the 1100KV.
Ideally you will want the 2.8 diffs, which will help the lower RPMs of that motor. The sensored part is what allows it to take off so smoothly.

As a heads up you will need to beef up the drivetrain to handle that power. It would bend the stock dog bones like wet noodles!!!!

If I could afford the scorched titanium axles and spool setup along with this motor and ESC combo I'd probably keep my Limitless and speed run it more. As of right now that car is likely going to be sold soon.

Thank you. I will definitely do all of that. The motor in the combo says it's 800kv

And btw, I can get the combo for $300

 

[LibertyMKiii]

Thank you. I will definitely do all of that. The motor is the combo says it's 800kv

Id recommend trying to get the 1100kv. I read on FB last night that it is out of stock currently.
Also from experience it tends to be best to order direct from Castle incase you need anything for warranty reasons.

https://www.castlecreations.com/en/...c-with-2028-1100kv-sensored-motor-010-0167-02

 

[rotauq]

I read everything. It's my first introduction to it. It's not the easiest stuff to understand. I have an opportunity to buy a combo with that motor so I thought I'd ask a question.

Sorry, no personal attack, no hard feelings. You are welcome to ask questions. And LibertyMKiii is definitely one of the best to answer any. I was just a shocked you made the conclusion that low kv would be a bad choice.

 

[bkhlouf]

No worries, we all have to start somewhere. If you have the budget for it... that setup is killer with the 1100KV.
Ideally you will want the 2.8 diffs, which will help the lower RPMs of that motor. The sensored part is what allows it to take off so smoothly.

As a heads up you will need to beef up the drivetrain to handle that power. It would bend the stock dog bones like wet noodles!!!!

If I could afford the scorched titanium axles and spool setup along with this motor and ESC combo I'd probably keep my Limitless and speed run it more. As of right now that car is likely going to be sold soon.

No doubt about the 2080 1100kv motor to handle extensive speeds! A couple of questions:
What gear should I target? What do you mean by 2.8 diffs?

 

[Fallguy]

Sorry, no personal attack, no hard feelings. You are welcome to ask questions. And LibertyMKiii is definitely one of the best to answer any. I was just a shocked you made the conclusion that low kv would be a bad choice.

No need to apologize, I didn't take it as an attack at all. I'm a gas airplane guy, this electrical stuff is new!

 

[LibertyMKiii]

No doubt about the 2080 1100kv motor to handle extensive speeds! A couple of questions:
What gear should I target? What do you mean by 2.8 diffs?

Depending on what vehicle you start out with for the build they have different ratios in the differentials.
The Limitless and V1 Infraction have 3.3 differential ratios. (Same for Typhon)
The Infraction V2 and Felony's front diff are 2.8 ratio.

For a low KV motor this 2.8 ratio diff helps a lot as visualized here. (8s setup with voltage drop guessing around 25v and BSR foams)

Original Limitless 3.3 diff

Same exact setup running the 2.8 ratio diffs:

This scenario netted around 17mph more with the same pinion and spur used. This will help you get to higher speeds due to gearing limitations.
The 29T optional Arrma Spur gear would also further help this.

 

[bkhlouf]

Depending on what vehicle you start out with for the build they have different ratios in the differentials.
The Limitless and V1 Infraction have 3.3 differential ratios. (Same for Typhon)
The Infraction V2 and Felony's front diff are 2.8 ratio.

For a low KV motor this 2.8 ratio diff helps a lot as visualized here. (8s setup with voltage drop guessing around 25v and BSR foams)

Original Limitless 3.3 diff
View attachment 128852

Same exact setup running the 2.8 ratio diffs:
View attachment 128853

This scenario netted around 17mph more with the same pinion and spur used. This will help you get to higher speeds due to gearing limitations.
The 29T optional Arrma Spur gear would also further help this.

Thank you so much. In fact, I recently witched my both diffs to GP5 as part of my ongoing limitless upgrade. So this a good news for me.
In fact, after I posted my question I realized the 2.8 was the diff ratio. That I already took in consideration during my research for my upgrade.

Thank you so much. In fact, I recently witched my both diffs to GP5 as part of my ongoing limitless upgrade. So this a good news for me.
In fact, after I posted my question I realized the 2.8 was the diff ratio. That I already took in consideration during my research for my upgrade.

One more thing, I term of gearing i elected to start with S/P 39/34 on 8s what do you think ?

 

[Fallguy]

No worries, we all have to start somewhere. If you have the budget for it... that setup is killer with the 1100KV.
Ideally you will want the 2.8 diffs, which will help the lower RPMs of that motor. The sensored part is what allows it to take off so smoothly.

As a heads up you will need to beef up the drivetrain to handle that power. It would bend the stock dog bones like wet noodles!!!!

If I could afford the scorched titanium axles and spool setup along with this motor and ESC combo I'd probably keep my Limitless and speed run it more. As of right now that car is likely going to be sold soon.

NM answered it myself

 

[Fallguy]

Depending on what vehicle you start out with for the build they have different ratios in the differentials.
The Limitless and V1 Infraction have 3.3 differential ratios. (Same for Typhon)
The Infraction V2 and Felony's front diff are 2.8 ratio.

For a low KV motor this 2.8 ratio diff helps a lot as visualized here. (8s setup with voltage drop guessing around 25v and BSR foams)

Original Limitless 3.3 diff
View attachment 128852

Same exact setup running the 2.8 ratio diffs:
View attachment 128853

This scenario netted around 17mph more with the same pinion and spur used. This will help you get to higher speeds due to gearing limitations.
The 29T optional Arrma Spur gear would also further help this.

I have been reading through this thread several times. Was able to get the castle 2028-1100KV motor. I downloaded that app and was going to figure out what size pinion etc. Please correct me if I'm wrong but doesn't the limitless roller come with a 2.8 ratio?