[wubbert]

Don't forgot :

http://www.e-traction.nl

http://http://www.e-traction.nl/proj...g-test-vehicle

[DrOof]

Hm. Their 470 mm wheels looks suitable for a sedan size car. But at 70kg of unsprung weight...? Could that be an issue?
Also, any indication of costs?

[iti_uk]

Originally Posted by yosemitesamiam

Spinning creates gravity, it doesn't reduce it.

Spinning creates gravity? Please cite something which supports this, I've never heard that before. If you mean to be talking about centripetal forces, then yes.

Also, what do you envision your 80kW per wheel vehicle capable of doing? That's 320kW total - that's 430hp! And probably more torque than you could use.

Daanii, I'm also planning a similar vehicle to the one you describe. Mine won't be a hypercar, so I'm looking at using four 12kW motors with a 5:1 reduction gearset for each - plenty for a sub-1 tonne commuter, I'd expect...

Chris

[wubbert]

Originally Posted by DrOof

Hm. Their 470 mm wheels looks suitable for a sedan size car. But at 70kg of unsprung weight...? Could that be an issue?
Also, any indication of costs?

They teach u that school, but attach plates of 70KG on youre rear wheel
It feels fine!!

The wheels under the Mercedes G are even 150KG (old prototype wheels)
And it handles great!

The wheels are still prototypes,so now the are too expensive..but give it time!
The 470's wil be pefect under a sedan/saloon/station!

[wubbert]

Originally Posted by iti_uk

so I'm looking at using four 12kW motors with a 5:1 reduction gearset for each - plenty for a sub-1 tonne commuter, I'd expect...

Chris

Please look for direct dive, reduction is noisy and kills youre efficiency

i'm planing a reverse trike with these wheels:
electric_car_hub_motor_7kw

[iti_uk]

Originally Posted by wubbert

Please look for direct dive, reduction is noisy and kills youre efficiency

I'd be using a planetary gearset, the efficiency of which would be up in the 90% range. I'd rather take the slight hit on mechanical efficiency for a torque multiplier than increase the current and copper mass of the motor for acceptable low-speed acceleration.

Originally Posted by wubbert

i'm planing a reverse trike with these wheels:
electric_car_hub_motor_7kw

Interesting motor, but I want to avoid in-wheel motors.

Originally Posted by wubbert

They teach u that school, but attach plates of 70KG on youre rear wheel
It feels fine!!

The wheels under the Mercedes G are even 150KG (old prototype wheels)
And it handles great!

Unsprung mass effects the ride quality, NVH and performance of your vehicle.

A heavier wheel will require a stiffer spring to maintain contact with the road on un-billiard-table-like surfaces, and a stiffer spring will require harder damping to avoid under-damped, "bouncy" suspension. The combination of both will increase the harshness of the ride and will increase stresses on the various suspension mounting points on the vehicle, possibly requiring reinforcement and therefore further vehicle mass increases.

A heavier wheel will also act as a flywheel (multiply by however many wheels you have on your vehicle). 70kg of added rotational mass on each wheel would certainly kill acceleration and will have a negative effect on braking performance.

To say that adding 70kg to each wheel resulted in a vehicle which felt "fine" means that either you were driving on a billiard-table-smooth surface without fast acceleration or deceleration, or you were barely moving at all. Or your judgement of "fine" needs recalibration... I can feel a difference on my current car, between "normal" wheels and "lightweight" wheels, and the difference there is only a few kg per wheel, let alone 70kg!

Not to mention that 70kg on each rear wheel or driven wheel (in my case it would be four wheels) represents a huge chunk of the total vehicle mass. 280kg just for the wheels? I'd expect the entire rolling chassis to weigh less than that!

This is not to say that a car with 70kg wheels would not literally work, but in the same way, using lead-acid cells will work, it's just far from ideal.

This is not just "school textbook" stuff, this is measurable and can be felt in practice too. There is a reason why OEMs spend so much money trying to reduce the unsprung mass on the vehicles they produce.

The only way the 150kg wheels on a Mercedes G would feel "fine" and would handle "great" would be in the same way that running 100m while carrying your partner on your back is "possible" or the way that the food in the canteen at work is "edible". All of these things under normal circumstances are best avoided.

Chris

[MalcolmB]

That's a good summary Chris. Have you already found a source for your planetary gearsets or do you intend to build your own?

[iti_uk]

Originally Posted by MalcolmB

That's a good summary Chris. Have you already found a source for your planetary gearsets or do you intend to build your own?

I'm currently considering Perm-Motor's PMS 120 (water cooled), and their site suggests that gearing is available. I need to contact them to find out the nature of that gearing - if it's not suitable I'll get hunting for off-the-shelf solutions, although having a set of gears manufactured is not impossible, although I'd like to do some level of durability simulation before hand and I don't have direct access to the solvers at work.

Chris

[palmer_md]

First time I saw this thread title, I thought of this vehicle. Then I saw the date and realized the Rimac ConceptOne had not been released yet. I still think this drive-train packaging is absolutely fantastic. Love the 4 motors and gearbox setup as well as the 20aH cell packaging.



http://www.rimac-automobili.com/conc...ntroduction-20

[MalcolmB]

Sounds good. It's been a while since I looked at the Perm motors. 800 Nm at the wheels and sub-1000 kg should be quite nippy. Since you're going for four-wheel drive I'm guessing you have some ideas for playing with traction control?