I took Flecc's advise - and created a monster...

[am001]

A long while ago, I posted a question on here, and Flecc gave me some advise to get in contact with OnBike. http://www.pedelecs.co.uk/forum/electric-bicycles/5977-who-can-help-me-please.html#post76976

I took my lightweight Marin steel framed 700c hybrid, and put on the kit and it did everything it said on the tin. The 300rpm motor in a 700c wheel, with the current capacity of the LiFePO4 battery gave me about 23mph on the flat without pedaling and going to 27.4mph(my record) pedaling hard. it cruised at 25 with normal pedaling which was fantastic. The problem was, that with the motor on the front, the vibration from the poor roads, speed bumps and farm track sections of my commute were killing me. I was getting to work with sore shoulders, and not using that speed for large parts of the journey.

I decided that I could build something better.
Knowing a bit about suspension (my father is a suspension designer for LGV and HGV) I did my research and bought a lightweight cross country mountain bike frame from ebay (Boardman FS) that has a virtual pivot type geometry at the back. This, along with the motor power smoothing the motion would ensure no bobbing. I welded an extension onto the back of the frame, to allow me to swing a 700c road wheel, and to adjust the geometry so as to have a virtual pivot that suited the larger road chainring I wanted. I bought (ebay again) a 700c 65mm travel suntour air suspension front fork with remote lock, and built up the bike, mainly from ebay. Total cost just over £300.

Because of the rear suspension I couldn't have a 'proper' rear carrier for the battery, only a seat post fixing, and the battery weight on that caused major handling issues, I built the battery into a custom aluminum box in the frame, which has the weight exactly where I want it, and still uses the key mechanism to unlock it so as to remove it for security and charging.

All I can say is that it flies. For my application, a mix of road, farm track, speed bumps, potholes etc. it is perfect. The top speed hasn't changed, but the average speed has increased considerably. The worst section of track with speed bumps I used to take at max 10mph for fear of removing my teeth. This thing will take them at 20mph and is comfortable enough I don't even stand out of the saddle. My commute has come down from 18mins to about 15. added bonus is I now have big disk brakes, which are phenomenally efficient and still work in the wet!

I can really recommend OnBike. There have been a few issues (battery bms failiure), and I have been quite particular about what I wanted, and they have been superb throughout. Thanks guys, and thanks to Flecc for starting this!
see a picture here:

Andrew

 

[eddieo]

sounds like a smashing bike! and battery where it should be.....It is a pity that only BionX have managed to do this in a stylish way.

unfortunately your link does not bring me to any pictures

 

[am001]

sorry try again with the picture....

I have tried hosting the picture somewhere else, hope this works...

 

[flecc]

Glad it all worked out in the end Andrew. I don't like suspension for road use but agree that a front motor can produce harsh reactions into the handlebars for those who like more comfort.

For off road/farm track riding I can well imagine how uncomfortable it would have been and how much better it is now with suspension. As you've found, the eZee kit is a great performer and it all sounds very enjoyable.
.

 

[eddieo]

I have tried hosting the picture somewhere else, hope this works...

you can load a picture using "tiny pic"

TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

 

[am001]

you can load a picture using "tiny pic"

TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

Nice, Thanks!

 

[Scimitar]

Nice build. Just keep an eye on the front dropouts.

 

[Mussels]

That looks really good, is rear suspension viable now?

 

[flecc]

is rear suspension viable now?

I think it depends on the intended rider input and surfaces ridden.

On a moderate power road system where rider effort is a big component like a Cytronex, rear suspension would be
very wasteful of effort and spoil the bike.

For am001's use of a powerful motor at quite high speeds on farm tracks it can become an asset for comfort.
am001 is riding on the tracks at below the top speeds so well within the motor's capacity to deliver what's needed,
so the rider input is a smaller proportion of the whole effort and less prone to losses.
.

 

[am001]

suspension

Its also a carefully selected geometry, suspension design has come on a lot since the single pivot trailing arm type.

There are lots of fancy names for different designs but this is setup so as when the suspension moves, then alignment of the top and bottom link are such that the pivot point of the suspension always goes through the point of the top of the chainring, i.e. the point of pedaling force. If it were above the chainring, then the tension from your pedaling causes the back wheel to move down, if the below then the wheel moves up as you apply pedal force i.e. bobbing and power loss.
There is a really nice explanation on Ellesworth bikes website (promoting their version of course) Ellsworth Handcrafted Bikes

Because I extended the rear triangle by cutting and welding plates into it to accommodate the bigger wheels (700c instead of 26") and because I wanted a larger 48T chainring to keep up with the motor, I had to draw out and plot the movement of the rear and calculate the new pivot points so as to make sure that I didn't get any losses and bobbing.

I don't feel any rear end loss with this setup even pedaling with no electric power. There is certainly bob in the front forks if I stand up to climb a hill, but that's what the remote locking forks are for

With this, I can hit speed bumps and fly off kerbs and belt down farm tracks with impunity. It becomes invisible, and you can concentrate on the riding, which I need to across that terrain at that speed!

I can recommend it

BTW can anyone recommend suitable winter/wet/mud tyres? my marathon plus ones are good in the dry but a bit lethal in more than a shower....

Andrew

 

[jbond]

Nice machine. Could you give us a few specs? Is that a Puma motor? And what voltage and controller are you running?

 

[weirdfish]

Excellent job on the battery box.

 

[NeilP]

What would happen if you want to change the big ring at the front to a bigger one again? say a 50 or 53 or 54 would that upset the rear geometry and require a new rear plate welding in, or is there enough 'give' in the design of the pivot points of the rear geometry/

 

[flecc]

Its also a carefully selected geometry, suspension design has come on a lot since the single pivot trailing arm type.

Very true, vastly different from the awful swing arm and rubber bung still found on some folders and even the odd
larger design, e.g. Giant Revive.
.

 

[am001]

What would happen if you want to change the big ring at the front to a bigger one again? say a 50 or 53 or 54 would that upset the rear geometry and require a new rear plate welding in, or is there enough 'give' in the design of the pivot points of the rear geometry/

It probably wouldn't be a big deal, as once you reach those sizes, the effect on the radius of the extra teeth is smaller, so a 48T to 50T is only 4mm difference in the radius. There is always some compromise as you can only get it right for one chainring, so you move more than that moving to the middle chainring as you change gear. I chose to optimise it for the biggest ring as I will be doing higher speeds. The bike by default is setup for the middle ring at 32teeth, which was a big difference.

The other consideration I had was that the frame was only really designed for 44T max being a mountain bike, and 48T was the largest I could squeeze in before it hit the stays.

Andrew

 

[am001]

Nice machine. Could you give us a few specs? Is that a Puma motor? And what voltage and controller are you running?

Hi,
Its an eZee kit, as recommended by flecc. 36v 8Ah LiFePO4, twist throttle, normal eZee controller and a 300rpm geared motor in a 700c wheel (approx 550W I think although they don't seem to publish the power)

The photo is a bit out of date now, I have got some mudguards on it (essential as the weather gets worse), and some custom built lights created from 2x 6W MR16 LED lamps from eBay approx 10W and 1400lumens for £30!! voltage regulation built in for 6-24V, so I have two in series and they're awesome. Better in my opinion than some of the £200+ LED light sets you see, and they run right from the 36v battery. As there is so much interest I'll try and get a better picture up.

Andy

 

[flecc]

Its an eZee kit, as recommended by flecc. 36v 8Ah LiFePO4, twist throttle, normal eZee controller and a 300rpm geared motor in a 700c wheel (approx 550W I think although they don't seem to publish the power)

It compares with the SB motor and eZee controller combination that they used to use, and their old Torq 1 showed measured peaks of around 1000 watts and could easily sustain over 550 watts continuous, despite the legal rating.
.

 

[jbond]

It compares with the SB motor and eZee controller combination that they used to use, and their old Torq 1 showed measured peaks of around 1000 watts and could easily sustain over 550 watts continuous, despite the legal rating.
.

So that's a geared hub motor with a freewheel? Does anyone know the make?

300rpm+700c = ~40kph = ~25mph So I wonder what the no-load rpm is. Assuming it is a geared freewheel type, what speed does the power cut out?

 

[am001]

So that's a geared hub motor with a freewheel? Does anyone know the make?

300rpm+700c = ~40kph = ~25mph So I wonder what the no-load rpm is. Assuming it is a geared freewheel type, what speed does the power cut out?

If you pick up the front of the bike so no load it will go to 28mph on the speedo, not sure what rpm that is. What I find is nice is the assist fades slowly away as you go over 23mph until its gone at about 27mph. Some bikes I rode really feel like you just hit a mud puddle as the assistance just stops dead once you reach the limit.

I ordered a cycle analyst from OnBike on Friday, so next week I will be able to tell you exactly the numbers....

 

[flecc]

It's eZee's own design motor. With 9 years established using three other types of hub motors they've gained loads
of experience so went their own way.

The no-load speed on the comparable Torq 1 with the SB motor/eZee controller combination was just touching
27 mph, so very similar set up here.
.