Trek Cytronex - First Impressions.

[john]

I admit to no longer being a physicist, but it seems to me that when you climb you are also accelerating to defeat gravity (9.8m/s/s downwards).

Chris

It takes force to move the wheel vertically in order to overcome gravity but it takes no more force to keep the wheel spinning (at constant speed) when you are moving vertically (or a slope) than when you are moving horizontally.

BTW, I don't deny that you are noticing something when you use lighter wheels going up hill, I just can't say what the physics is.

 

[flecc]

Big picture though, a bit of weight can make a few seconds difference, which matters a lot to someone in a race, but on my commute to work, a few minutes either way is not significant!

On an e-bike the success/failure hinge point becomes important in a way it isn't so defined on ordinary bikes. Example on my Q bike (Quando) climbing my home 1 in 7 on a one third discharged battery:

With my weight and bike's climbs without pedalling.

With 5 kilos of shopping added it still just makes it.

With 7 kilos it has no chance, reaching stall point.

So there's a make or break single kilo in there. The percentage importance of that depends on the percentage share of rider effort when pedalling, but it's a factor that isn't anything like as identifiable to a precise point on unpowered bikes.
.

 

[coops]

Weight at the wheel rim counts twice as much as weight on the frame, but only for acceleration, not hill climbing.

Apologies for the confusion (& now total derailment of the thread Chris!) arising from my incomplete statement of this 'rule': what John has said is what I meant, Chris, and I was thinking about acceleration (though without saying it explicitly) rather than hill-climbing . Apparently it takes twice the energy to accelerate wheel weight as it does the same weight on the frame, 'as a rule'. Whether the weight distribution also is a factor I don't know but I'd guess that weight on the rim makes more difference like you say Chris, so maybe those high spec wheels help you accelerate into the hill & boost your initial climb speed & confidence with it .

This is because the wheel rim travels at twice the speed of the frame and so must be given twice the acceleration to achieve this. That isn't an issue when traveling uphill where all weight counts the same (including the weight of the rider!)

Another way to say it (if I remember right...) is that that the rotational forces necessarily produced within the wheel when its rotational speed increases (i.e. during acceleration of the bike) are, coincidentally, equal to the force that is required to accelerate just the mass of the wheel (without rotation) to the speed of the bike. Therefore to accelerate and rotate the wheel takes twice the force it would if it wasn't rotating, and since the force required is proportional to the mass and the acceleration, weight on the wheel counts for twice the same, non-rotating, weight elsewhere on the bike when acelerating.

That the wheel is rotating is the reason the wheel speed (at the top of the wheel) is twice the frame speed (since the rotation speed of a point on the
tyre edge must equal the road speed, unless the tyre is slipping), so what I said is equivalent to John's explanation (but just a bit longer!).

As for the implications for hub motors, cytronex (mmmm... lemons!) etc....

Stuart.

 

[Chris_Bike]

In a vain attempt to get this thread back on track

So I've decided to stop worrying why light wheels are better on hills and just enjoy the bike. It's a fabulous evening and I've taken a circuitous route to the pub. Holland are 2 nil up and I'm having a small pint before enjoying a leisurely ride back. Fantastic!

Chris

 

[Cyclezee]

Chris,
I have also made a decision, I will ignore posts from non Cytronex owners, that only leaves you and the lady with a pannier on each hip who has yet to comment, I will just form my own opinions when I get the bike.

What exactly is a small pint? Are you feeling under the weather?

J hn

 

[Chris_Bike]

A small pint

Well, it's actually a pint (as opposed to 2, which you later pretend was only one although nobody believes you). 18.3 miles at any average of 12.5 with power on low pretty much anytime I wasn't actually going downhill. I like this bike more and more.

Hope your's comes soon John.

Chris

 

[flecc]

Well, it's actually a pint (as opposed to 2, which you later pretend was only one although nobody believes you). 18.3 miles at any average of 12.5 with power on low pretty much anytime I wasn't actually going downhill. I like this bike more and more.

Hope your's comes soon John.

Chris

18.3 miles per pint, that's 146.4 mpg. Not bad.
.

 

[Chris_Bike]

18.3 miles per pint, that's 146.4 mpg. Not bad.
.

I guess it would get me into the lowest CO2 emission band for car tax and the congestion charge!

 

[coops]

Personal impressions give a useful idea of the 'feel' of a bike, aswell as its performance with a particular rider, but it is very difficult for others to extrapolate from such personal experiences what performance they may get from the same bike (such as whether it will cope with their terrain or give sufficient range): calculating the power output from just the bike's battery & motor, then combining the rider's pedalpower with that, can give a roughly accurate and useful guide to performance limits for anyone, which can if necessary be fine-tuned with experience rather than innaccurately derived from it in the first place.

Stuart.

 

[Chris_Bike]

Calling John (Aldby)

This is another attempt to get back on track. I'm travelling back to B'ham on Virgin Trains on a lovely sunny evening. I intend to get out on the Trek later. Incedently the lady with the panniers nailed to her hips is very happy with hers too (she just thinks I'm mad talking to myself on this forum!).

Chris

 

[Cyclezee]

Chris
No, your not mad, it is everyone else hope you enjoy your ride this evening, but be wary of those pubs, they can be a real hazard when cycling

J hn

 

[Chris_Bike]

Another 14 miles

I was a bit later out this evening and kept the route minimal. 14 Miles, but still taking in Forhill (the 1 in 7 with bits of 1 in 4/5). Motor on low power all the time (you need to remember to re-activate power after braking, but I'm getting good at that). Average speed 13.2 - significantly, that's only a tad above the speed it wants to go on low power (12.5), suggesting that the battery/motor did a fair bit of work. There seemed to be plenty of life in the battery when I got home, but I didn't want to keep going round the block, so I don't know how much. Now I have established the way I like to ride this bike, I will try a more scientific range test when I can. 136 miles on the odometer now.......

Ps. It was Hereford Pale Ale tonight John - one of my all time favourites!

Chris

 

[flecc]

Is it easy to swap batteries if a spare is carried Chris? Apologies if this has already been covered previously.
.

 

[Chris_Bike]

Yes, very. The battery connector is a multi-pin plug that tightens on the battery via a simple twist fitting, I probably intend to buy a second battery which could be best carried in a second bottle carrier on the seat tube. I am waiting to assess range in Wales when I can get out there. Around Birmingham I seem able to get the claimed 20 miles per charge quite easily.

Chris

 

[flecc]

Thanks Chris. The range in Wales will be interesting when you get a chance to assess that, and a second battery will make that easier to do.
.

 

[john]

I was wondering about the battery. My guess is that it is two strings of AA's in parallel. They must be good quality to withstand the 4C current requirement though.

 

[Chris_Bike]

I did discuss the batteries with Mark when I decided to buy the bike. I know they tried batteries from several suppliers before they settled on the ones they currently use. Their batteries also have a built in voltage regulator providing ~7v for the lights.

I have been working from home today. Started at 7.30 so, at 12.30 when the sun came out, so did I! I'm having a serious attempt to assess range. I'm in the Warwickshire countryside between B'ham and Stratford. The terrain is rolling - not the 1 in 4/5 on the way back from my usual pub, but plenty of hills. Apart from a couple of times when I used high power to get past any ill-mannered bus and safely cross a roundabout that enters the M42, I have had low power on ALL the time. I've just stopped for lunch at Lowsenford (12.5 miles) so I should manage to run the battery down on the way back.

I'll tell you later!

Chris

 

[Chris_Bike]

27.9 miles!

Yes folks, that's the distance I have just ridden before the battery failed.....

To recap, my ride was south of Birmingham in the Warwickshire countryside. Out through Shirley towards Henley before turing for Losensford, Lapwoth and back via Earlswood Lakes. Its constantly rolling. No 20% but plenty of 10% hills and above. I left the power on low ALL the time. If I cut it by applying the brakes, I turned it straight back on, even if I was going down hill. Of course, the motor cuts out at 12.5 mph anyway on low power mode, but riding this way means I get help on all hills and when accelerating away from anything that has slowed me down.

My average speed was 13.6 which is, of course, above the 12.5 mph cutout and I look forward to another flurry of posts teelling me that I can only get this performance out of the bike because I am so fit. Whilst I am enormously flattered (and greatly amused) by the theory that I am some kind of cross betwen Lance Armstrong and Eddy Merckx, this notion is not only wildly inaccurate, it also misses the point. I think the Cytronex performs so well because it is so easy to ride, with or without motor assistance. The drag on the motor hub is negligable and the weight and general standard of equipment just make for a nippy ride. I can ride it at 15mph on the flat with ease and I genuinely believe that most of you could too.

That is the real genius of this bike and why distances like 28 miles are possible. As discussed with Flecc last night, the real test comes with my shopping run in Mid-Wales. That's a round trip of 16 miles, about 7-800 feet downhill then the same back up. We will see, but I am begining to think that it may be possible on a single battery (which I certainly didn't believe when I bought the bike).

BTW for the real cynics out there....... No, I don't work for Cytonnex, I paid the full price for both our bikes and I don't expect any favours from the company for posting my honest assessment of their bike. I truly think it is awesome and I would recommend anyone to try one out if they are looking for an Ebike. I know that other Forum members will be getting their bikes soon, so I lookforward to seeing if they agree.

Chris

 

[carpetbagger]

thats a pretty impressive mileage Chris,,,given tha batteries are only £150 each you could get another 2 and have a real touring machine......

 

[john]

More questions out of curiosity...

Do you have the 160 rpm or 190 rpm motor?

If you lift the front wheel off the ground, what speed does it do on the two speed settings?