# First Post :) Let me know what you think



## 3dplane (Feb 27, 2008)

Hey Zozie!
First welcome to the forum! 
Wow that is some serious equippment. Knowing my self,my first test run would be one of those motors mounted on the back with whatever prop it can swing and a cage around the prop....no loose clothing.
If you really gonna go that rout I would like to hear from you how is take off from a dead stop,due to the nature of the motor and speed controller.
When they are used as they were originally intended there is virtually no load untill the prop hits certain rpm therefore starting is not an issue, but since I'm toying with the same idea (big BLDC) I often think about how to solve the startup issue when used in an EV. I've ran large (homemade) BLDC on a bycicle before but power was applied after takeoff. That is the only thing making me curious but considering the available power you gonna have it will probably not be an issue. 
How are you going to gang the two motors together? Any plans yet?
Barna


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## zozie (Sep 11, 2008)

I already have some sprockets made for that motor. The'll be sitting beside each other and one of them will have a one way bearing so it can be switched off when not in use. That motor has enought power to turn a 40X22 prop so power should be ok but I'm just worried about the starting toque as well considering the small diameter. Anyways I'll have the motors next week along with the controllers so I can do some tests with lead acid batteries. I'm fairly hopefull about starting power as those batteries have huge discharge and I hear rumors of a new LIPO from Thunder power with 40C continous discharge and 65 burst
I'll post some videos when I fire up the motor.
Zoltan


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## zozie (Sep 11, 2008)

Well I got the motors and controllers, I'll be doing some power testing with lead acid batteries tonight. I'll post pix as as well. Got the whole bike stripped down. No more engine


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## frodus (Apr 12, 2008)

good luck on the project.... I always wondered about RC stuff and EV's (I used to have tons of RC stuff, but downsized).

I wouldn't think those motors are going to have much low end torque, even geared the way you want. Are you using the original transmission? or just direct drive like the rest of us? If you do direct drive, it won't use the original ratio, transmissions have a primary gear reduction, a 1/2/3/4/5th gear reduction and the final drive ratio of the sprockets. In 1st gear, my VFR originally had a 19:1 ratio or somewhere near that. The sprockets only gave it a 2.8 ratio. You WILL have to replace the front/rear sprockets.

8000RPM, and a stock gear ratio isn't going to want to move that bike very well... those motors are wound for high speed, not high low end torque. Even with my motorcycle, and a 30Hp motor made for low end torque (50ftlbs), it had problems accelerating from a stop with a 4:1 ratio.... stock was ~2.8.

Another thing that'd help, is a torque curve of those motors. If you can get that, I can help you figure out if they're going to work out the way you want. I've done all the calcs with my motor.

I'm just curious what kind of torque you get out of these. It'd be interesting to gear these up to a smaller wheel and see what kind of pushing power... maybe on a scooter... just for a trial.


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## zozie (Sep 11, 2008)

I know I'm worried about starting torque as well. I'm using right now a smaller motor form the same mfg. in one of my BIG helis, but there it's running at a constant RPM. I'm beginning to think of a scooter now as well. Maybe one motor in the front wheel and one in the back?
Anyway joking aside I'll get the power curve. Can't wait to try them. I'm actually thinking of just buying an electric scooter and tearing it down to put my motors in it with the LIPO batteries. I can see some problems tho with the discharge of the packs below 10 degree C tho. we'll see. I'll try the motors today, try to load them up somehow. We'll see what kind of power I'll get.


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## 3dplane (Feb 27, 2008)

Zoltan!
I just thought of something while yapping on the other thread.
It is very important that when you get the bike all hooked up and ready to go, something has to be done to avoid blowing up the controller(s) on deceleration from higher speeds. I've done it my self (blew a cc 25) on decel with my bycicle. And I've heard someone blew a cc HV 110 with a motorcycle on decel. It is never an issue when using these controllers the way they were meant to be used, so we don't think about it but they do not take power generation from the motor very well,regardless whether you program brakes on or off. I would just hate to see that kind of distruction over something so easy to forget about. 
By the way I have no doubt once you are in motion that sucker will pull even from low rpm. Unfortunately it's a sensorless setup if I'm not mistaken so it needs to be spinning for the controller to...take control after the initial bump over. Well keep us updated 
Thanks Barna


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## zozie (Sep 11, 2008)

I'm surprised you even used a CC25
Why on deceleration??


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## 3dplane (Feb 27, 2008)

zozie said:


> I'm surprised you even used a CC25
> Why on deceleration??


Thats what I had laying around and I was ready to go...kind of like you are now that you have the stuff. Sooo.. how big a prop you got for that first quick test run I was talking about?.

Back to the controller blowing: Why on decel? Simply these controllers are made to push power towards the motor and are not setup to handle current coming back towards them. The brake feature is just to stop a prop not an EV with rider/driver. Some of the "controller guys" could probably give a little more scientific answer than mine however I'm not sure who's familiar with the rc type brushless sensorless setup.
For my future ones I was thinking maybe a disconnect(between motor and esc) of some kind but then reconnecting while coasting will shock the crap out of the controller. Actually it would be nice if some of the "chip heads" (please dont be offended,you know who you are ) would chime in on this issue. Thanks Barna


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## zozie (Sep 11, 2008)

*Re: First Post  Let me know what you think - Power will be OK for sure.*

Well I can verify that it spins a 32X12 prop at 8200 RPM at 48 volts with 90% throttle curve. I didn't do any higher cause Mejzlik says it will snap at around 8K
Man you should feel the wind comin' off it
I made a video as well I'll put it on youtube tomorrow at work. I am now confident that 2 of these beasts will pull my virago 250 with ease. Somehow I gotta try what kind of torque I can really get off the line before I go thru the headache of installing it and killing my credit on Lipo batteries. I did contact Hacker Deutschland about the power curve but I haven't heard back as of yet.
Just to give you guys a hint about what revving a 32X12 R/C prop at 8200 RPM, 100 - 150CC 2 cylinder engines can barely do that at 15-18 HP

Pix are coming tomorow

PS. I guess I won't really find out about low end torque until I get the LIPO batteries as their discharge is insane compared to ready to go batteries you buy for electric scooters. Just a few more weeks and there will be FlightPower Evo packs with 40C continous and 60C burst discharge....


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## 3dplane (Feb 27, 2008)

That's awesome!
Something about batteries my friend recently discovered: the little 7AH field battery( sealed ) cranks the snot out of his 7500w generator! And they can be had for somewhere around $14 wholesale. To top it off the little battery was sitting on his shelf for four years with no charging!
This one is a hangar 9. Don't know if they still make them with that kind of C- capability but it's something to consider. Barna


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## 3dplane (Feb 27, 2008)

Ok I'm worried now!
I hope you didn't throw a blade at 9000 rpm or something and got hurt.
Hope you're just busy. Post something!
Barna


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## zozie (Sep 11, 2008)

NONONO I'm good I've been just really busy this week and I haven't touched anything in a few days. This weekend I'll start putting the motors on the bike's frame and start a real build thread.


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