The BPM case:

flat section: 22km, maximum speed: 42.4km/h: 31 minutes 10 seconds, no pedalling.

3.5km 10% hill section: motor running at 700W + cyclist 132W = 832W, climb speed: 13.1km/h * 832/711=14.14km/h: 15 minutes 15 seconds

Total in ideal condition: 46 minutes 25 seconds

To get the best of the BPM, you'll need 48V 20A continuous discharge. For the best result, I reckon the BBS01 at 48V would win the race.

Thanks, but I meant 26.5 km/h - whoops!

22km @ 26.5km/h=49 minutes 48 seconds no pedalling

The hill climb remains as it was (15 minutes 15 seconds)

Total time 1 hour 5 minutes

The flat portion can be done more quickly than that but Iif the motor cuts out, then you are effectively limited by legalisation.

"Or equally I could ease off a bit on the effort I put in, so the ride takes the same amount of time, but I'll be using loads less effort which will mean I'm fresher in the evenings or weekends to go on actual rides."

 

The beauty for me is the flexibility. My commute is 10 miles with big long hills which I was doing on a hybrid (pre conversion) taking about an hour each way. It was OK when I was feeling up for it but 5 days a week, all conditions (weather and personal health) it was a bit gruelling. My fastest time was 50 minutes pre conversion. Now with my little Q75 and 2.3Ah battery I do it in about 50 minutes as a matter of course. I also find that I get still get a seriously good workout as its fun going really fast up steep hills, especially flying past lycra cyclists. And its been a godsend in the recent gales.

Using the numbers to predict savings is great and very interesting, certainly something that I think could be used to generate a nice simple webpage that gives people an indication of the times / effort they could save if they plug in their distance / fitness level / bike details etc etc and then it could work out the numbers.

 

Does this already exist somewhere? Perhaps this site could have a page that does this?

 

However it doesn't really take account of the slow speed sections where most time and effort gains happen. My commute isn't really that typical as there are hardly any corners or lights, its just one straight road - so I don't really stop at all, so didn't benefit from these gains.

 

Most commutes for most people will involve lots of stopping and starting, and its these 0 - 20mph accelerations where most of the time gains happen.

 

The other benefit of eBikes that I think aren't talked about often enough is the fact that you get away from lights really quickly meaning you are much safer and also the support at these low speeds really helps people who arent so confident getting up to speed on a bike.

 

My results really show improvements in time, when I actually wasn't expecting any, due to the nature of my commute and the fact that I thought I'd be able to go above the assist speed for most of it. The fact its a benefit for me, means it should benefit lots of others a LOT more.

 

The second thing about the graphs I've shown so far is that my commute home is more downhill than uphill, so again I didn't expect the impact of the eBike to save as much time.

 

Cheers

Col

With a derestricted 8-Fun BPM and a throttle, you can get home in about 45 minutes without pedalling.

 

That's amazing, I had no idea they were so powerful, you'd need a huge amount of battery power though. I'd still need to see someone do it to believe it.

On an unrestricted bike, you can do the same flat section in half the time, 30 minutes.

You should be home in 1 hour 7 minutes with a legal bike, 45 minutes with a derestricted Bosch bike.

 

There's a proviso, though. The battery consumption when running a derestricted crank drive bike at maximum speeds on the flat is comparable to a very steep climb. A 400W/h battery will exhaust very quickly indeed if run full-tilt throughout.to get theoretical high-Watt performance for 30 minutes straight.

 

Also the bike needs to be one which is racing-friendly design, motor designed for speed rather than climbing torque, and bike set up for speed (low rolling resistance tyres and "aero bod" on it etc.), or the theoretical performance will most likely not actually be seen. In practice, I would bet that few of the regular Bosch bikes (even if derestricted) would be capable of sustaining 28mph on the flat for very long before performance starts sagging .

In practice, I would bet that few of the regular Bosch bikes (even if derestricted) would be capable of sustaining 28mph on the flat for very long before performance starts sagging .

 

The Panasonic S bikes are commonly capable of 25 miles range on the 26 volt 10 Ah (260Wh) battery when fully using their performance (Top speed up to 26 mph depending on the fitted gear system). Even the smaller Bosch battery is 288Wh so should return somewhat similar.

Maybe without a torque sensor fitted ... perhaps it's coupling these claims with the Bosch-style torque sensor systems which doesn't sit right with me. You'd be busting your a**e to get the bikes to deliver that and your consumption measurement would be through the roof.

 

I still don't believe you'd get that time achieved. Someone needs to prove it in practice .

Artstu's derestricted KTM Macina Cross with Nexus 8 seems to be capable of doing this in 45 minutes.

 

It's a good bike, certainly not perfect, but I got it at a very good price. I've done around 1800 miles I think.

 

Here are some issues to take account.

 

The rim brakes aren't that good in the rain, they cover the bike in black stuff, they wear the pads very quickly, and no doubt the rims too.

 

The hub gears and wider chain suit crank drive better than derailleur systems, but the chain still wears quickly with all the power it has to cope with. I've fitted a chain tensioner to mine, it is essential IMO, it makes taking up the play quick and easy. I replaced the first chain at about 1500 miles.

 

With the standard speed restrictor the bike was barely faster than my old training bike on some routes, now it powers to 32 mph that isn't an issue. I had to gear it up a little to take advantage of those speeds. An 11-speed hub would be better in that respect.

 

The hub geared Bosch bikes are power/torque limited to save the hub compared to derailleur ones, I'm perfectly happy with the power it gives though.

 

The small 300 w/h battery can be all used up in just 16 miles in hilly terrain. Once you've got used to full assistance it is very hard to bring yourself to turn the power down. I now have a 400 w/h battery as well to allow me to go a bit further.

 

Before I got the bike I only cycled on the flat due to a long term illness, now I can go anywhere even though I limit the power I put in.

 

The Bosch system with the speed tweak does exactly what I wanted an e-bike to do, for me it really is a joy to ride.

I guess on the right e-bike there's a 20 minute ish gain to be had on your commute each way for the same input from yourself as you'd give on the racer.

 

Artstu's derestricted KTM Macina Cross with Nexus 8 seems to be capable of doing this in 45 minutes.

 

Indeed, just like I said earlier in the thread.

I still don't believe you'd get that time achieved. Someone needs to prove it in practice .

 

I may be tempted to give it a go in the summer

The various calculations on this thread make a diverting read on a rainy Sunday.

 

But has any account been taken of head - or tail - wind?

 

A stiff head wind can increase battery power consumption by 50 per cent or more.

 

Lots of restarts can also have an impact - it's one of the reasons why your car uses loads of juice in city traffic.

 

Predicting a journey time is fairly easy, but all the variables make predicting power consumption very difficult.

I cruise at 26-28 most of the time, on either sport or turbo, and i always get at least 20 miles out of it. Usually that's with lots of stop-starts in the city centre, so i'd expect a touch more on rural roads with similar gradients.

The calculator says that you need approximately 500w to maintain 24 mph on the flat with no headwind. Assuming that an average rider can maintain a comfortable 100w for an hour, the remaining 400w would exhaust the battery in approximately 20 miles. That's without stop-starts, and in ideal conditions.

 

You need about 1000w to maintain 30 mph. If the battery could maintain 900w, range would be down to about 10 to 12 miles.

Maybe the batteries are under rated, this would also help companies live up to their longevity claims.

 

I know in general with my RC batteries, that if i buy a 5000mah pack, it'll usually charge up to 5500-6000mah, at least until it's pretty well used. Due to charging them at very high currents and discharging them very quickly too, RC packs have a fairly short life compared to Ebike batteries, 50 full cycles and they're done.