Wheel Hub Motors: Are they viable yet? - DIY Electric Car Forums
Go Back  

DIY Electric Car Forums > EV Conversions and Builds > All EV Conversions and Builds

Register Blogs FAQ Members List Social Groups Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
  #1  
Old 05-16-2017, 12:59 PM
USAVeteranRealtor USAVeteranRealtor is offline
Junior Member
 
Join Date: May 2017
Posts: 4
USAVeteranRealtor is on a distinguished road
Default Wheel Hub Motors: Are they viable yet?

I am doing the research side of things for a possible electric motorcycle build i would like to perform in the near future. I have a friend that i ride on a regular basis here in South FLorida that owns a Scorpion P6 motorcycle. I have gotten the chance to ride in it a handful of times and absolutely LOVE the bike, but the bike has 2 major flaws that i think can be fixed with an EV version of the motorcycle.

Issue 1) The single rear wheel drive setup works flawless if you drive the motorcycle under the limits of the rear wheel traction. The 600cc engine has little to no issues with breaking the rear wheel loose when you give it more than 1/2 throttle in the first few gears, so acceleration is vastly limited due to that, and it gets scary in the corners if you give it any acceleration coming out of a corner, the rear wheel just wants to spin.... So going to a FWD setup would fix this issue easly.

Issue 2) The cooling system is very tiny on the bike, it is perfectly capable of maintaining engine temps when driving in a normal manner, but if you accelerate hard or do any type of spirited driving, unless your doing 45+mph the engine gets extremely warm and has boiled over a handful of times while riding it spirited through the city. The owner is on his 2nd engine due to the first one overheating on a track day he did and warping and cracked the head...

My question is this... Have any wheel hub motors become viable yet in regards to reliability. I looked into this a few years back when i converted my catrike expedition to electric with a hub motor and nearly everyone told me that they were junk, that the wires would overheat at the center with any type of spirited driving.

Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old 05-16-2017, 02:35 PM
major's Avatar
major major is offline
Senior Member
 
Join Date: Apr 2008
Location: Ohio, USA
Posts: 7,308
major is a jewel in the roughmajor is a jewel in the roughmajor is a jewel in the rough
Default Re: Wheel Hub Motors: Are they viable yet?

Yup. Wheelmotors still suck for anything larger than a bicycle or small scooter.

edit: here's one of my favorite threads on the subject:
http://www.diyelectriccar.com/forums...ble-20591.html

Last edited by major; 05-16-2017 at 02:58 PM.
Reply With Quote
  #3  
Old 05-16-2017, 03:07 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 167
brian_ is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

There are endless announcements of hub motor designs, and they all share the same problems:

Unspung weight is important to ride and handling. An electric motor of sufficient power (even for one wheel worth of propulsion) is heavy. The motor's weight can be minimized by operating it at high speed, but that means lots of gear reduction, which means a heavy, bulky, and expensive pile of mechanical hardware riding with the hub... increasing weight and packaging problems.
Electric-assist bikes and similar vehicles routinely don't even have suspension, negating this concern.
High power density leads to the need for cooling, which means hoses carrying liquid coolant between the motor and radiator. While many (probably most) DIY EV conversions make do with no more cooling than a fan on the motor shaft, continuous-duty motors in commercially produced electric vehicles are typically liquid-cooled. With a wheel motor, that means hoses running along the suspension links, flexing with suspension travel, and flexing through even greater angles with steering.
Electric-assist bikes and similar vehicles typically run only a few hundred watts, which is relatively easily dissipated through the surface area. This is a scaling issue - sometimes smaller is easier.
One reason to use a hub motor is to avoid the need for a jointed shaft to connect the hub to a motor or transmission... but those shafts are very effective and reliable, while a hub motor setup requires that the electric power cables flex with suspension and steering movement.
The cables for an electric-assist bike's hub motor are thin, minimizing the problem - this is the scaling issue again. Similarly, electrical cable to a wheel speed sender is not a problem, because the wires are thin.
Although most braking effort for an electrically-driven wheel should be regenerative action by the motor, a mechanical brake is still needed to supplement regenerative braking, as a backup, or for parking. That's difficult to package in the hub assembly with a motor (and likely gearing as well). I noticed that a recent design actually used a drum brake, because it was easier to package than a disk brake, even though drums have long been obsolete for automotive use other than for parking.
Reply With Quote
 
  #4  
Old 05-16-2017, 03:16 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 167
brian_ is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Quote:
Originally Posted by major View Post
... here's one of my favorite threads on the subject:
http://www.diyelectriccar.com/forums...ble-20591.html
Thanks
I'll apologize for having responded (my post above) without looking at this thread. I still haven't read the whole thread yet, but the fact that the person proposing to produce hub motors as a commercial product doesn't understand the meanings of "rotor" and "stator" is not a great start... and another dozen posts in he's talking about 96 volts of lead-acid battery, so it's not about wheel motors for a serious roadgoing car. Into post number twentysomething and we see that he was planning on an open motor, exposing the flux gap to road debris and brake dust!

Last edited by brian_; 05-16-2017 at 03:32 PM.
Reply With Quote
  #5  
Old 05-16-2017, 04:27 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 167
brian_ is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Still reading the old (started in 2008) wheel motor thread...

It seems to me that many people proposing designs (such as the original poster in that thread) don't know much about automotive design. That's okay - I don't know much about inverter design, and we all need to start somewhere - but in many cases it seems like they haven't even taken a wheel off a car and looked at what is there!

At post #80, ten months into the discussion, the original poster finally realizes that inboard brakes exist. That's not surprising since most people - even many auto enthusiasts - are not familiar with inboard brakes, but his reaction is either disturbing or hilarious: he proposes mounting the motors in the hubs and brakes inboard, still requiring the halfshafts and putting the heaviest and most complex parts bouncing around with the hubs! Not a lot of rational thought going on here...
Reply With Quote
  #6  
Old 05-16-2017, 04:33 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 167
brian_ is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

That classic wheel motor thread has a link (at post #165) into the middle of another thread. That one - open source hub motor/wheel motor - runs to 481 posts , apparently with no viable wheel motor appearing.
Reply With Quote
  #7  
Old 05-16-2017, 04:45 PM
USAVeteranRealtor USAVeteranRealtor is offline
Junior Member
 
Join Date: May 2017
Posts: 4
USAVeteranRealtor is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Thanks for the input, i was thinking this was the case still, just wanted to ask to see if something new and amazing had come out that changed the situation...

Another idea that has been bouncing around my head is placing the electric motors in the nose area of the vehicle in front of the passenger area which is typically filled with nothing or just the brake system. I could mount a pair of narrow motors so the shafts face outwards and possibly either gear drive or chain drive them to a centered area on the side of the passenger compartment which allows the ability to run a short axle from the output gear/sprocket to the wheel hub like how FWD cars are connected from the transmission to the front wheel hubs. Even if it was chain, probably be best to enclose it inside of something to prevent road trash on the chain and possibility of filling partially with oil/grease for lubrication.

I still have a lot to learn, but curious if most motors could be wired up to spin opposite at the same rate of increased speed via the motor controller? so the 2 motors in the front would be somewhat equal in acceleration...
Reply With Quote
  #8  
Old 05-16-2017, 04:58 PM
USAVeteranRealtor USAVeteranRealtor is offline
Junior Member
 
Join Date: May 2017
Posts: 4
USAVeteranRealtor is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Another option is the use of hydraulics. You could use 1 single larger motor mounted somewhere, then coupled to a common hydraulic pump which feeds equal pressure to either 2 front wheels or all 3 wheels equally being powered by the electric motor, but i feel like this would be the slowest and heaviest route of going about it.
Reply With Quote
  #9  
Old 05-16-2017, 05:57 PM
Karter2 Karter2 is offline
Senior Member
 
Join Date: Nov 2011
Posts: 1,286
Karter2 is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Quote:
Originally Posted by USAVeteranRealtor View Post
My question is this... Have any wheel hub motors become viable yet in regards to reliability. I looked into this a few years back when i converted my catrike expedition to electric with a hub motor and nearly everyone told me that they were junk, that the wires would overheat at the center with any type of spirited driving.
Reliability of direct drive hub motors is the least of their issues for vehicles above 200kg or so.
Bicycle /trike conversions are viable up to 3-5 kW , beyond that, the weight of motor and battery begins to move things up to a different power league.
Infact any "direct drive" ( motor running at wheel speed) becomes unattractive at those 200kg+ weights where torque becomes a serious requirement, and hence gear reduction between the motor and wheels is beneficial to get useful torque and efficiency.
There are several electric fwd "mototrikes" already available if you are looking for inspiration.
However, if i were building it, i would keep it simple with a geared ( chain) drive to the rear from a single chassis mounted motor, and solve the traction and handling issues with weight distribution and wheel/tire selection.

Last edited by Karter2; 05-16-2017 at 07:32 PM.
Reply With Quote
  #10  
Old 05-16-2017, 07:07 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 167
brian_ is on a distinguished road
Default Re: Wheel Hub Motors: Are they viable yet?

Quote:
Originally Posted by USAVeteranRealtor View Post
Another idea that has been bouncing around my head is placing the electric motors in the nose area of the vehicle in front of the passenger area which is typically filled with nothing or just the brake system. I could mount a pair of narrow motors so the shafts face outwards and possibly either gear drive or chain drive them to a centered area on the side of the passenger compartment which allows the ability to run a short axle from the output gear/sprocket to the wheel hub like how FWD cars are connected from the transmission to the front wheel hubs. Even if it was chain, probably be best to enclose it inside of something to prevent road trash on the chain and possibility of filling partially with oil/grease for lubrication.
After wading through the 39 pages of the other thread, I went for a walk and thought exactly the same thing: presumably the space directly between the front wheels is foot room, and so the interest in wheel motors, but you can still have individual motors without mounting them out at the wheels.

A more fundamental question might be why use this vehicle design, if radically changing the way it works? Three-wheelers have substantial challenges in dynamic behaviour, and the change from driving the rear wheels to driving the fronts has consequences. As Karter2 suggests, a more suitable design makes more sense.

Quote:
Originally Posted by USAVeteranRealtor View Post
I still have a lot to learn, but curious if most motors could be wired up to spin opposite at the same rate of increased speed via the motor controller? so the 2 motors in the front would be somewhat equal in acceleration...
I believe the answer is 'yes' regarding reversing motor rotation direction. Although some in this forum will tell you that individual motors are crazy and unworkable - and I agree that controlling them appropriately would be a challenge for DIY project - they are now done in a few production vehicles, so it is certainly a viable approach. Of course, every wheel motor design requires the same control of independent motors, but none of them have made it to production.

Last edited by brian_; 05-16-2017 at 07:15 PM.
Reply With Quote
Reply

Share or Bookmark this

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

 
Support DIY Electric Car
Sponsors

All times are GMT -6. The time now is 02:53 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Ad Management by RedTyger