Custom Full Suspension Flatbar Road bike build

Kepler · Nov 27, 2011

Now that summer is upon us, I am taking the opportunity to ride to work whenever possible. For this I wanted a quick efficient commuter that provided good comfort on less then perfect bike paths but still had similar efficiency to a road bike. Also wanted to have enough assist to make the trip nice a quick without me needing a shower when I get to work.

The frame is a cheap but robust dual suspension Alpha Atomik mountain bike frame that is tall enough to fit 700C wheels and still provide good front wheel to toe clearance.
Good quality wheels were of utmost importance and as such a set of White Industries disc brake compatible hubs were laced into 700C rims and then fitted with 32mm tyres.
Suspension is RockShox entry level but plenty good enough for commuting duties.

Now to the drive. Friction drive of cause but mounted in a fairly stealthy location and utilising the bike stand mounting platform for attachment.

The plan is to use 3 x 6S 5000 packs mounted inside a Topeak seat-bag. Will be using a CA-LRC for throttle interface and a Turnigy 100A esc limited to around 500W via the CA

All up weight will be around 17kg which I think is quite reasonable considering the bike has dual suspension.

Justtoby · Nov 27, 2011

Love it.....now that IS stealth!

dogman dan · Nov 27, 2011

No kidding, I thought it was before pics. Like the idea of skinny 700c rims on the bouncer for a commuter. Once you have disk brakes, no need to match rim size for the brakes to work. Cool. Battery carried in a fanny pack or something like that?

Might pedal bob a lot compared to a hardtail, but just crank down the rear shock till it's tolerable, and you still have plenty of shock for the potholes and rough surfaces.

Pure · Nov 27, 2011

I'm with you Dog, I thought this was the "before" pic.

I love it. Def thinking outside the box.

Racer_X · Nov 27, 2011

WOW! that is stealth! I did not notice it until the Third time I looked. That would definitely mind f***K those lycras!
I love it. No more "Cheater" comments unless you totally ride without pedaling.

Pure · Nov 27, 2011

I'd like to see a video of it running so we can get an idea of what kind of sound is going to come from a setup like this.

veloman · Nov 27, 2011

I love this build. Efficient and comfortable, very stealth. You gave me an interesting idea with the 700 wheels on a mtn bike. How much was the bike/frame? Looks great for an ebike.

Drunkskunk · Nov 27, 2011

wow. thats impressive

Kepler · Nov 27, 2011

Thanks for the positive comments everyone. The fact that the drive was not obvious to you guys certainly ticks off the stealth requirement for me. Other good thing is that the drive setup is well proven and although configured slightly differently to cope with the underslung position, should be just a plug and play affair. Hopefully I will get to test this in the next day or two. Testing a new friction material too so I am interested to see how this stands up.

I have been riding my Bomber to work on a regular basis but do get concerned that I am pissing other riders off especially on the busy paths. The plan is to put knobbys back on the Bomber and return it to serious off road duties. Looking forward to really pissing of the Lycra's with this new ride when they cant work out why they cant keep up. :twisted:

Noise wise, at 500W these drives are not too bad at all. Its when you start to push 1500W through them that they start to sound like a miniature turbine.

Anyway, more photos to follow of the drive unit in closeup and the completed bike of cause.

Kepler · Nov 27, 2011

veloman said:
I love this build. Efficient and comfortable, very stealth. You gave me an interesting idea with the 700 wheels on a mtn bike. How much was the bike/frame? Looks great for an ebike.

I bought the complete bike off ebay about 2 years ago for about $400. Changed out the suspension, bars, and pedals and of cause the wheels. I still have the 26" MTB wheels with knobby's that it came with so I can fit them straight back on if I want to use the bike off road also. I havent seen the bike for a while though.

adrian_sm · Nov 27, 2011

you beat me too it. :lol:

What motor did you end up with. I found it necessary to go for a narrower motor and trimmed shafts to set it up in that spot and clear chain rings, cranks etc. Does the bike have a wider BB? That would help open up motor options.

I recommend the topeak aero wedge large. It nicely fits 3x 6s5Ah Turnigy packs with a bit of breathing room, or 4x5s5Ah just. But that gives you long cable runs to the new drive location, so be careful of inductance voltage spikes.

You are building quite the stable of ebikes there buddy. :mrgreen:

Kepler · Nov 27, 2011

The motor is an EMP 6354 200kV from Leader Hobbies. Everything clears nicely with this motor. I think the BB is just a standard width on this bike. I will use the Topeak aero wedge large for sure and have a couple of these that I have using for ages.

The long distance between motor and battery did worry me a bit but it actually isn't too bad. With the ESC in the middle, I have added 150mm extensions to the motor side and only a 100mm extension on the battery side. this gives me cable to spare.

Yep the collection of ebikes is building up but not quite out of control yet.

ohzee · Nov 27, 2011

Damn that sure is pretty. Great work.

Hillhater · Nov 27, 2011

kepler,
do you need any "Spring assist" to launch the motor into contact with the tyre. ??

veloman said:
. You gave me an interesting idea with the 700 wheels on a mtn bike.

you do know that you can get 26" x 23mm "road race " tires to fit MTB rims ?
much cheaper than a full 700c wheel conversion. :wink:

adrian_sm · Nov 27, 2011

That blue "grip tape" is pretty funky. What's it made of?

Oh and nice torsion spring.

Kepler · Nov 27, 2011

Hillhater said:
kepler,
do you need any "Spring assist" to launch the motor into contact with the tyre. ??

Yes it uses a balance spring to make the motor neutrally buoyant. you can see the spring in the first picture a couple of posts ago.

When the motor is in a hanging position like this setup and gravity forcing the motor away from the tire, the spring is wound up in a direction that neutralizes the motors weight. The end stop is then adjusted so that the motor just clears the tire. With the over the tire config as per my seat mount setup, the spring need to wound to in the opposite direction to ensure it stays clear of the tire. In both cases the torque reaction of the motor on start-up then give enough movement to have the motor touch tire for launch.

you do know that you can get 26" x 23mm "road race " tires to fit MTB rims ?
much cheaper than a full 700c wheel conversion.

Really? Smallest tire I have seen that fits a 26" rim is 32mm and even that was a suspect fit.
Either way, for best efficiency, the 700C rim is going to be the best option simply due to the larger diameter. Totally agree though that a 700C conversion is not a cheap option.

Kepler · Nov 27, 2011

adrian_sm said:
That blue "grip tape" is pretty funky. What's it made of?

Its a hard rubber matting used for non slip flooring. A mate of mine dropped over a sample to me a while back. I though this would never work but decided to give it a go about a month back. To my surprise, it actually showed a bit of promise. Tends to wear to the shape of tire but grips well and is kind to the tire. Biggest issue so far has been keeping it stuck to the motor casing but the contact method seems to be holding OK. The matting can be found in Bunnings if you want to give it a go. They will cut a small strip of it if you ask.

Oh and nice torsion spring.

You like that?

Made out of 2mm Piano wire. Works very nicely but I wouldn't like to make too many by hand that for sure.

adrian_sm · Nov 28, 2011

Kepler said:
You like that? Made out of 2mm Piano wire. Works very nicely but I wouldn't like to make too many by hand that for sure.

:lol: Been there done that. Exactly why I got a bag of them wound to my specs.

You should bring this bike along for the group ride on the 10th, chuck some spare lipos in a backpack if you are worried about range. Swing by my place and we can ride in together, which way were you going to come in?

Kepler · Nov 28, 2011

Probably will take this bike in for the ride on the 10th with a few extra LiPos. Sounds like a plan to ride up together. Probably head up Canterbury Rd towards the city.

SamTexas · Nov 28, 2011

Took me 10 mins to find the motor, and that's after all the warnings for other members. Great job! Can't wait to see the finished/completed bike and the test results.

kmxtornado · Nov 28, 2011

Justtoby said:
Love it.....now that IS stealth!

But it'll look a lot different once the batteries are placed. I'm curious to see how it turns out. Looks great so far.

Kepler · Nov 28, 2011

Oh so true. Nothing like a bunch of batteries to spoil the stealth effect. Still, you be the judge, but I dont think looks too bad fully loaded ready to go.

Before Batteries, Controller and CA.

Fully Loaded ready to go

Kepler · Nov 28, 2011

A few more shots of the bike ready for its first serious shakedown.

I have loaded just two x 6S 5000 packs in the seat bag. This gave me room to fit tools for a tube replacement and spare tube.

Kepler · Nov 28, 2011

First serious ride was from Melbourne Eastern Suburbs to the city. This was all on bike tracks and around 30km in total. The bike performed flawlessly with the ride being so much more comfortable then my carbon road bike. Efficiency was better then expected and managed 6.6 Whrs/km. Riding style was relaxed pedaling and speeds as fast as what was safe for the type of track I was on. Typically this was 30kph to 40kph with 30kph needing around 300W and 40kph around 500W.

On the 2 x 6S 5000mah packs, the low voltage cutout of 20.7V kicked in at the 27km mark. Leaving me with a few kms left to finish the ride.

The new grip tape stood up quite well also. You can see a bit of wear in the middle and I expect the peaks to be knocked off in the centre over the next we rides. Actual grip was great with no slip even with the contact kept quite light. Also went through a few puddles with no noticeable slippage on the way out.

Kepler · Nov 29, 2011

Ride back home was interesting. Temperature was very warm and humid and the plan was to take it easy on the way home. That plan soon went out the door when I came up a against a very quick Lycra. Managed to pass him after some hard work and then stopped at a crossing for a bit of a chat. He was really impressed and ended up drafting me for the next 10km with me going flat out. He stayed on my tail for the full distance. So much for a relaxed ride home. Ended up being a good test for both the bike and me.

Efficiency was still quite good despite the higher speeds. Still managed 7.5Wh/km but needed the third battery to get me home.

The only casualty was the grip tape. This started to delaminate towards the end of the ride. Upon closer inspection it looked like the heat build up had made the plastic go brittle. Oh well, it was worth a try. looks like its back to using the bare metal of the motor can. This still seems to be the best overall option even if it does require more contact pressure and doesn't work in the wet.

Custom Full Suspension Flatbar Road bike build

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