Buying an Astro motor

[waxman123]

Ok going to buy an astro motor for my mountain bike build. Questions:

1. what is the number of turns mean? How does this affect performance?
2. will the 3220 handle more heat than the 3120?
3. does the 3220 have alot more torque than the 3120?

Thanks

Erik

 

[johnrobholmes]

Ok going to buy an astro motor for my mountain bike build. Questions:

1. what is the number of turns mean? How does this affect performance?
2. will the 3220 handle more heat than the 3120?
3. does the 3220 have alot more torque than the 3120?

Thanks

Erik

More turns = slower and more torque per amp. Less turns = more power and faster speed. All else held equal.

The 3220 has about 50% more can area than the 3210, if my memory serves me right. It will not handle more heat, and it has less area for dissipation per volume of stator. For a particular power level, it will run cooler however.

A 3220 will be able to produce twice the torque of a 3210, with unlimited amperage and all else equal. Torque has a 1:1 positive linear relationship with stator and magnet length.

 

[recumpence]

John is correct.

I can help you decide on the correct KV (RPM per volt), motor size, and other bits for your application. Astro motors are great in that they are custom made for each application.

Matt

 

[waxman123]

Wow thanks for the quick response John and Matt!

Ok MAtt here is what I want to do. I have finished a build (see pic) after burning up 3 V3 1000 BMC hub motors (they did take care of me on warranty) I went to a cyclone motor build. I will probably never do a hub motor again until they fix the heat and torque issues! Build is:

29 Intense (5 inch suspension)
cyclone 48 V 1000 watt custom welded to frame, chain driven to front cranks (freewheel) to the rear Rohloff rear 14 speed hub. 48 V 15ah Lithium battery in backpack

This set up has been very durable and if you keep the watts around 1500 average overheat is to a minimum. It does have a heat cut off. Torgue is great for climbing hills and top speed on flat is 28 no pedal, and 35 plus if you pedal.

What I want to do on this next build is incorporate and make everything more compact. Plan is to put the batteries and the motor is a box like set up on the down tube like the like the Norco build. The great build the guy did on the Norco MTB bike from Australia.

This build is going on a Yeti ASR 7. I have or will be ordering the following:
1.ASR 7
2. 6 Thunder power 22.2V 5000mah to run in series and parallel to get 48V and 15 ah. Thanks matt this works really well!!!
3. Rohloff rear hub
4. A 25:1 side drive reducer from anaheim automation. These very small and can handle up to 18,000 rpm input and 10,000 out put are maintenance free and on the expensive side but I have a in with my company.
5. Castle HV 160 ESC plus a throttleizer from EV logics. Thanks Andrew
6. Either a 3220 or 3210 from astro flight. Turns?

What I want is compact, lightweight, very few wires. Everything is going to be on the bottom tube in a box type set up. top speed 35mph no pedal and plenty of torque for hills (Rohloff seems to help with torque thru the gears)

Questions remaining.
1. should I stay with 48V or go to 36V.
2. Motor size and turns.
3. is my 25: 1 reducer enough? ( they have 1 to 100 reduction) I know I am going to loose efficiency but hoping the power of the Astro will conquer this.


Thanks

Erik

 

[recumpence]

OK, a few things jump out at me.

#1 I would go with Flightmax cells from Hobby City. They are about 1/3 the price of Thunderpower. I am a fan of Thunderpower stuff. But, for the quantity of cells we need, the Flightmax cells save a fortune.

#2 The Rohloff hub may not take the power of the Astro. They are rated for 1,500 watts. I know they will take more. But, a $1,400 rear hub is an expensive item to risk. That being said, we are all very interested to see someone use one in this application. So, in to that end I say, go for it! But, do so at your own risk.

#3 As for motor RPM, the Astros run most efficiently (for the most part) at about 7,500 RPM and really like to run 10,000 RPM. So, with a 48 volt pack, that puts you at about 200 to 230 rpm per volt to get you in the sweet spot.

Next you have to consider the ratio. At 25 to 1, a 10,000 RPM motor would be reduced down to around 300 RPM (shooting form the hip, here). Then you will be running an additional reduction from the output to the cranks. That output would be something like 3 to 1. This gives you a max crank RPM of 100. THat is a little high, but doable. So, maybe a KV of about 170 or so. That will get you closer to the output RPM you will need.

Beyond that, the sky is the limit!

I can tell you the HV160 is a great little controller. I have been messing around with them for a while now and the only issues I have had are related to innitial arming. So, I would recommend using a 10 watt 1 ohm precharge resistor and 2,000mf additional capacitence at the input of the controller. You will, also, want to set the PWM rate at 24khz for these motors. This is an easy program setting within the controller. You also will definately need the USB programming cable for the controller. When you get to that point, we can go over the specific settings to get it running for your application.

Matt

 

[waxman123]

MAtt
I have read about the Optibike using the rohloff with 0 problems. I think their setup up is 36V 1000 watts with a BB motor with a ton of torque. I talked with the Rohloff people and they were excited about me trying this for EB. They are thinking this could be a new untapped market and they think their hub is up to the task. As far as offering me a replacement at cost if it all goes south!

Ok I am down to this with the battery and motors:

Astro 3120 at 48V. Now how many turns 7 = 194 or 8 = 169. I would like more top end speed as the rohloff has a ton of torque for the steepest of hills so far! What does the "best amp" mean on their PDF description?

I will go with the Flightmaxx batteries thanks for that tip!

Matt I look forward to having a conversation with you when I get further along on this project. I have changed the type of bike I am going to use. I will not be using a Yeti as I found out they are Manfactured in Taiwan. I will be using an Intense, Ventana or Ellsworth. Going to get as many things made in the USA as possible!!!!!!!

Thanks
Erik

 

[Ypedal]

Get the 3220 !! for the power you want to pull.. :wink: .. i have the 3210 and am pushing it hard, it does good but the 3220 would do more ! hehe

 

[waxman123]

Ypedal
watched your 10 minute video racing around town man I can not what to get mine going!!!

How manny turns was your motor on your 3210!!! I think I am going to go with the 3220 now! Just how many turns in the questions!!!

 

[etard]

Erik,
Good on you for supporting the local economy!! Speaking of Intense, I googled bike shops while in Temecula, CA and up popped Intense, so I hopped over and just wandered into the frame shop. It is really cool to have a company so successful and still made in the good ol US of A. Can't go wrong with an Intense. Maybe you can have them weld on mounting tabs before they heat treat your frame so that nothing is weakened by the motor mounting process? Please start a build log as you get closer to assembly.

 

[GGoodrum]

Just a couple of points. A 12s LiPo setup is actually 44V nominal, not 48V. A 48V 16s LiFePO4 setup actually has a nominal voltage of around 52V. Under load, the LiPo-based 44V pack will not sag much at all, while a "Ping"-type LiFePO4 will have a bit of voltage sag, under load. Not nears as much as with SLAs, but they will sag, when pushed. The point being that the performance under load will be similar. The LiFePO4-based setup will have a higher top speed, though, when there's not much load. Anyway, when figuring out which kV/wind you get, you should use 44V to figure out top speeds and gearing.

On 12s, a 3220-4T, which has a kV of 169, will run around 6500-6600 rpm, when you factor in efficiencies, etc., so with your 25:1 reduction, that will be down around 265. All you'd need to get this down to a cadence of, say, 90, would be a reduction of around 2.9:1. Using a 16T freewheel off the output of the reduction unit, to 46t chainring would come pretty close, at around 2.875:1. That would be a cadence of 92. If you used a 48t/16t combo, the reduction is 3:1, so the cadence would be around 88.

-- Gary

 

[MitchJi]

Hi Erik,

Maybe this will help you decide on the kv:
http://endless-sphere.com/forums/viewtopic.php?f=30&t=16728&start=240#p263843

Winding it to have a lower KV means less power. The copper fill dictates the torque ability, and the RPM range enables that torque quantity to become power.

This is why anything that gives it a higher speed range by XX% will give a higher power output ability by XX% as well. This is why right now, the limiting factor in the power output is the skirt bearing speed rating. The bell itself and the shaft bearings should all be fine well past 10,000rpm, which means having a 5,000rpm limit on the skirt cuts the power potential of the motor roughly in half. If it's a 12kw motor at 5,000rpm (entirely possible for it's stator size), with adquate voltage, it would be a 24kw motor at 10,000rpm.

I have read about the Optibike using the rohloff with 0 problems. I think their setup up is 36V 1000 watts with a BB motor with a ton of torque. I talked with the Rohloff people and they were excited about me trying this for EB. They are thinking this could be a new untapped market and they think their hub is up to the task. As far as offering me a replacement at cost if it all goes south!

1kw is totally different than 3kw-5kw.

I have changed the type of bike I am going to use. I will not be using a Yeti as I found out they are Manfactured in Taiwan. I will be using an Intense, Ventana or Ellsworth. Going to get as many things made in the USA as possible!!!!!!!

How about a Brooklyn Machine Works SR6, SR8 or Racelink? Chrome-moly frame and you could run the motor through the jackshaft:
http://www.brooklynmachineworks.com/
SR6:

Racelink:

 

[PowerPedro]

Nice project!! I wonder how is your progress? I would consider using a sensored motor which gives you better controll when starting up. I think it is possible to modify Astromotors in that way. Good thing would als be to measure the motor temperature to prevent overheating with an intelligent controller!! The only question is what controller could do this and handle a sensored Astroflight?