WhaTT for now

[Samcycles]

I came across this today and couldn't find anything on the forum about it so was wondering if anyone knows a bit more about it.
I've read through their website but can't find any mention of the motor size or if the throttle only works when you are pedaling so difficult to say if it would be road legal.

TT Messenger - The urban bike, lightweight & design

The TT Messenger invites you to change your outlook on the city and its surroundings. Weave through steep streets, extricate yourself from traffic, rethink your daily commute and turn it into a tailor-made suburban route in complete safety with maximum adrenaline.

www.whattfornow.com

 

[mike killay]

Well, they are very good at hype!
24 volt batteries are so out of date. and only 192 watt hours?
Seems to be an ordinary sort of thing, an ebike with an odd drive system (No gears, except for its central location it may as well be hub motor)

 

[vfr400]

There's a recent thread about it. To produce 160Nm torque at say 7.5 mph with a 29" wheel, it would be outputting 1510 watts. Let's say at an efficiency of 70%. That would be 2157 watts from the battery or 90 amps. It's puny 8Ah battery would last 5.3 minutes if it could manage that sort of current, which it almost certainly can't. My calculation using simple physics says somebody is telling porkies!

 

[Woosh]

My calculation using simple physics says somebody is telling porkies!

not necessarily. The torque value for CD motors is measured at the chainring - or motor spindle in this case. The BBSHD for example has the same 160NM max torque.

 

[vfr400]

not necessarily. The torque value for CD motors is measured at the chainring - or motor spindle in this case. The BBSHD for example has the same 160NM max torque.

What are you on about? It's not a crank motor and it has about 10:1 reduction to the wheel, so it would make 1/10th the torque at the motor.

 

[Woosh]

it is arranged in the same way as a crank / middle motor.

 

[vfr400]

it is arranged in the same way as a crank / middle motor.

Open up the link above, study the picture on the right, then come back and tell us how much torque you think the motor makes at 7.5mph hill-climbing speed. I'm going to say about 0.4Nm, which is some way off your 160Nm.

 

[Woosh]

it's a middle motor alright:

about the torque:
the rear belt cog looks like 20cm in diameter, I reckon the front cog may be 5cm, so you have about 4 front to rear ratio.
At max torque, you have at the rear 160NM/4 =40NM
It climbs as well as my Camino.
I said the bike was nice, not that it is cleverly designed.

 

[vfr400]

it's a middle motor alright:



about the torque:
the rear belt cog looks like 20cm in diameter, I reckon the front cog may be 5cm, so you have about 4 front to rear ratio.
At max torque, you have at the rear 160NM/4 =40NM
It climbs as well as my Camino.
I said the bike was nice, not that it is cleverly designed.

The ratio is actually 8:1. You're brain isn't working properly - the wheel rotates at 1.8th of the speed of the motor, so the torque multiplies, not divides. if the motor could produce 160Nm, then there would be 1280Nm at the back wheel and the MTB version claims 190Nm, so that would be 1520Nm according to your reckoning.


With the bike doing 7.5 mph, the motor unit output sprocket would be spinning at 746 rpm. Lets say that the 24v battery can supply 40 amps, which would be 960w input power or about 672w output power. That would be 8.6Nm at the motor unit and 68.8 Nm at the back wheel.

A normal 8Ah ebike battery can't supply 40 amps continuously, though, the best cells could do it for a burst. Lipos could give the 93 amps for 160Nm and 110 amps needed for 190Nm, but that would mean that it would drain the battery theoretically in 5 and 4.4 minutes respectively, but in practice, it would be much quicker, since batteries cannot achieve anything near their specified capacity when used at high currents.

You can't defeat the laws of physics. The battery has a pathetic 192 Wh of energy in it. You can take it out slowly and last longer or quicker, get more power, but not last as long. Lasting out 192wh for one hour would give you an average of 6.9Nm at the back wheel. A Cyclamatic can do that equally well and go for 25% longer.

 

[Woosh]

you are more right than me.
Perhaps they measure torque at the chainring rather than at the belt cog.

 

[vfr400]

you are more right than me.
Perhaps they measure torque at the chainring rather than at the belt cog.

AFAICS, the crank and chainring are conventional bike stuff and completely independent from the drive system.

That brings me to the next problem. Look at the gearing on the road version. They have a 10T top gear and only 32T chainwheel, so 60 rpm on the crank gives 192 rpm on the wheel, which is just about 15 mph. if you get a down-hill, you're going to be air pedalling. why did they fit a crank-set/gearset designed for uphill MTBing on a city bike?

 

[mike killay]

not necessarily. The torque value for CD motors is measured at the chainring - or motor spindle in this case. The BBSHD for example has the same 160NM max torque.

But surely that is only in bottom gear. Let's face it, if you gear the motor down enough you can produce huge torque.
I once got a car which would not start up a short but steep rise by removing the plugs and winding it on the starter motor.
This system does not have gears and so the whole purpose of central drive seems to be wasted.

 

[mike killay]

AFAICS, the crank and chainring are conventional bike stuff and completely independent from the drive system.

That brings me to the next problem. Look at the gearing on the road version. They have a 10T top gear and only 32T chainwheel, so 60 rpm on the crank gives 192 rpm on the wheel, which is just about 15 mph. if you get a down-hill, you're going to be air pedalling. why did they fit a crank-set/gearset designed for uphill MTBing on a city bike?

Once again a triumph of "DESIGN" and feelz over sensible, logical, practical pragmatism.

 

[Woosh]

AFAICS, the crank and chainring are conventional bike stuff and completely independent from the drive system.

yes, I am aware of that aspect. I suppose the 160NM number was given as a way to compare with other crank driven motors.

That brings me to the next problem. Look at the gearing on the road version. They have a 10T top gear and only 32T chainwheel, so 60 rpm on the crank gives 192 rpm on the wheel, which is just about 15 mph. if you get a down-hill, you're going to be air pedalling. why did they fit a crank-set/gearset designed for uphill MTBing on a city bike?

I didn't look beyond the aesthetics but TBH, it's only take minutes to change.