Medusa Afterburner V2 BL motors

Originally Posted by Unsullied_Spy

I like longer motors because they generate more torque, the more torque you have the less work the motor has to do. The problem is that they also draw more amps so you have to balance the length, KV, your batteries voltage, the weight of the vehicle, etc. It drives me nuts trying to decide which motor I want.

This is exactly my feeling too. Although the speedcalculator and these forums are a great help, it seems impossible to chose 1 motor and getting it right from the start, especially if your setup is different than common setups.

If I understand correctly:
- larger can motors with the same kv rating produce more torque than smaller can motors.
- lower kv motors produce more torque than higher kv motors with the same can length?

So if a have a setup geared for 40mph and I need more torque (and don't want to sacrifice speed) I could:
- get a larger can motor with the same kv rating;
- or go for a higher voltage setup with a lower kv rating/ same can length...

[Unsullied_Spy]

Originally Posted by drkdgglr

This is exactly my feeling too. Although the speedcalculator and these forums are a great help, it seems impossible to chose 1 motor and getting it right from the start, especially if your setup is different than common setups.

If I understand correctly:
- larger can motors with the same kv rating produce more torque than smaller can motors.
- lower kv motors produce more torque than higher kv motors with the same can length?

So if a have a setup geared for 40mph and I need more torque (and don't want to sacrifice speed) I could:
- get a larger can motor with the same kv rating;
- or go for a higher voltage setup with a lower kv rating/ same can length...

The larger can will provide more torque because there is essentially just more surface area. You get longer coils and thus a longer magnet (rotor) so even though it may be spinning at the same RPM, it will be able to provide more torque. Hopefully someone else can clear this up a little better.

A brushless motor's torque is largely dependant on amps. The KV rating tells you how many RPMs it will spin per volt applied, but the faster it spins per volt the more amps it needs to maintain that RPM. Theoretically, these Medusa motors are all capable of the same output (wattage) as long as they're the same size. A higher KV motor will require more amps and will drain the batteries faster while a lower KV motor will require fewer amps but more voltage.

If you're aiming for 40 MPH (very reasonable goal, according to BrianG's calculator my Muggy was doing around 45 on 5s with 40 series tires and a 2700KV Neu) and you already have your motor, it is cheaper to just get a smaller pinion gear. The smaller pinion gear will reduce the load you put on the motor, ESC, and batteries (reduce amp draw) which gives you more torque in 2 ways. The first way is you now have a shorter overall gear ratio, which is easier for the motor to turn, and the second is you are requiring fewer amps out of your batteries so if you really get it bogged down you have those extra amps to pull. If you aren't happy about the drop in speed, add more voltage. It's a good idea to aim your KV/voltage around 30-40k RPM though these motors can do 50k without coming apart (the bearings are rated to 60k, but you shouldn't need to push it that far).

This is where I get all confused. I spend a lot of time before buying a motor trying to balance out the weight of higher voltage packs with the amp output of the batteries I'll be using while trying to keep temps down. Technically the lower KV you run the better as long as you can feed it enough volts, but adding cells for voltage gets heavy and takes a lot of room. For a 1/8th Buggy or Truggy anything between 1500 and 2300 KV and 4-6s lipo (5-7s A123) should be fine though.

Sorry if I completely lost you, I just spent almost 8.5 hours at work so I'm a little out of it. Hopefully someone else can jump in and correct errors I've probably made

Originally Posted by Unsullied_Spy

but adding cells for voltage gets heavy and takes a lot of room.

As I understand, if you go for higher voltage and lower kv, you can get lower capacity amp packs. With 5s5000mah packs you should get about the same runtime as with 10s2500mah packs (both setups geared for the same speed). So the weight of the batterys should be about the same.

[Unsullied_Spy]

Originally Posted by drkdgglr

As I understand, if you go for higher voltage and lower kv, you can get lower capacity amp packs. With 5s5000mah packs you should get about the same runtime as with 10s2500mah packs (both setups geared for the same speed). So the weight of the batterys should be about the same.

In theory that sounds about right, but I think the 10s 2500 mAH pack would still be bigger. The weight should be really close though. The problem with running 10s is there aren't a whole lot of ESCs on the market to run that unless you get an air ESC and go through the trouble to make it work. MGM has some ESCs that'll handle it but you're looking at $500+ to get one. Lutach has a 10s ESC though, it seems to be pretty good so far. Not sure what price but they seem to be great ESCs for the price.

[rchippie]

Im looking for a few opinions, i just want to make sure i dont get the wrong motor. As some of you may or may not know i pre ordered a MEDUSA 70mm 2300kv motor to run on 4s in my GTP . Is this the right choice or should i get the 2000kv motor instead ?. I have recived a few opinions via pm's, & im looking for a few more . Thank's

[lutach]

Originally Posted by rchippie

Im looking for a few opinions, i just want to make sure i dont get the wrong motor. As some of you may or may not know i pre ordered a MEDUSA 70mm 2300kv motor to run on 4s in my GTP . Is this the right choice or should i get the 2000kv motor instead ?. I have recived a few opinions via pm's, & im looking for a few more . Thank's

The 2300Kv is good for 4S lipos as 300Kv isn't much when using such low voltage . I would have gone higher voltage, but if you insist on 4S then it's a good motor. It'll be spinning at around 34000rpm so it won't be running too hot, but that will also depend on your gearing.

Ahh the long awaited 70 mm motors are finally almost here! The 80s are a surprise tho, I had no idea they were doing them. Also, the 2 new 60mm ones are a nice addition too.

Wasn't sure if I should make a new thread or in here. Its a motor question, so I opted to put it in here, so I apologize in advance if it should have gone in a new thread.

Anyway, I have a question for you gents. I have the following packs and run this setup:

2 x 4s1p A123 packs, and 2 x 3s1p A123 packs

Kyosho Inferno ST-RR
MMM v1 - still going, fingers crossed
15/50 gearing with a Feigao 8XL 2084kv
4s2p A123

This setup currently lasts about 13min of race style driving. This was excellent when my club was running 6min heats and a 10min main. Having now switched to 10min heats, and 20 or 25min finals, its now a pain in the ass.

With only 2 4s packs, I can only do about half the final and then run out of packs. I was thinking that if I can run 7s1p packs and get 13-15 min out of them, then I can have a pack to change for the 2nd half of a 20min race. A 7s1p 2300mah A123 pack is equivalent to a 6s LiPo (same charged voltage, slightly higher nominal voltage).

Which 70 (or 80)mm Medusa should I be looking at to achieve my goal of getting 12-15min (or higher) run times from a 7s1p pack. Also, what gearing should I be looking at? I've got pinions from 12t - 17t.

I was thinking the 1600kv or the 2000kv 70mm.
Any thoughts would be greatly appreciated, thanks guys.

Oh yea, does anyone have an idea of when they'll be shipping the pre-orders?