Latest road and single track weapon.

Kepler

10 MW
Joined
Nov 8, 2009
Messages
3,922
Location
Eastern suburbs Melbourne Australia
So where do you go after a 12kW Stealth Bomber, custom Stealth Fighter, a weight weenie carbon super commuter? No secret I am a fan of Bafang mid-drives so it stands to reason this build would would be based on one of these. :)

So this is what I came up with.

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Bike_Full_on.jpg

The bike in its current configuration

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Base bike is an XLframe Specialized 29er Camber. Front Shocks are the stock 120mm RockShox Recon Golds. Rear shock is a DNM air shock which replaced the stock Ario Rockshox item for some extra travel and a bit more plushness giving a total 120mm of travel back and front.

A BMX style headstem was fitted to tighten up the reach and the chain ring side of the bottom bottom bracket milled down 4mm to 68mm to improve the less ideal chainline typically encounter when fitting a Bafang mid-drive.

A Bafang 750W BBS02 mid drive was then fitted complete with a 961 display unit. This is such an easy part of build and takes very little time to install. The modern curved lower down tube found on most good quality mountain bikes is not so good for providing an ideal platform for this drive and forces the bulk of the drive unit to hang quite low. Luckily the Camber has great ground clearance and even with the low mounting position, there is still 10" of clearance. As a precaution, a bash plate was fitted to protect the drive from any front impacts and hopefully allow the bike to skip over any logs. So far this has worked out to be a very effective solution.

A custom 104mm BCD chain ring adapter was machined up and fitted with a 44 tooth chain ring replacing the stock 48mm item. Main reason for this was to clear the chain stay but also to give the bike a little more torque for hill climbing.

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Next the stock thumb throttle was removed and a push button throttle fitted together with a micro switch activated by the gear selector to cut throttle when shifting gears. This required a simple dual voltage divider circuit to deliver a full throttle signal with the button and approx 5% throttle with the micro switch.

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Now to the battery set up. I quite like the simple front mount battery pack set up but wanted to do something a little different on this build. With the long down tube on this bike, it gave me the opportunity to design and install a long slim battery housing using 50mm square aluminium tube. I needed to fit the maximum amount of battery into this tube and found 3 x 5.8 ah 5s Zippy Compacts in a row to be an ideal fit. Battery cables were then brought up through the top via insulating grommets and series'd up across the top to make up a 15s 5.8ah pack providing 300Whr usable capacity. End caps were milled using machining plastic and an extruded aluminium cap milled down to size and fitted over the top of battery cables. The end caps are machined to match the frame tube profile and keeps the pack stable. A flat plate attached to the bottle cage blind nuts supports the bulk of the pack with the Velcro straps finishing off the mounting system. A permanently mounted volt meter was also fitted to keep an eye on charge level. So far just one of the batteries is monitored. This is mainly to keep things simple with the balance condition of the other packs checked manually on a regular basis

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For this bike to have a dual role, a second set of road wheels we're build for on road duties. Road wheels use mountain bike hubs laced into 700c rims. 25mm Gator Skins were then fitted for road bike like rolling efficiency. With 2 sets of fully built wheels including discs, conversion from on road to off road duties take just a minute or two.

Other modifications include custom programming of the BBS02 to remove all speed limits and to customize the levels of PAS to my liking.

Weight was an important factor in this build but more important was that the bike needed to be fast (in bike terms), handle great, and most importantly, a really comfortable ride. In relation to weight, in road trim, the bike tips the scales at 19.5kg (43lb) and in off-road trim beefs up to 23kg (48lb)

On road, the bike can sustain 45kph on flat ground with 35kph to 40kph being easy to maintain sipping around 250W. Pushing the throttle button boosts the power to 750W which is perfect for a boost up a hill if you need to shake off a persistent lycra who insists on sitting 3" off your back wheel for a free tow. This happened to me this morning and got a little tedious. After sitting behind him at speeds between 30kph and 35kph, I rang my bell and overtook him to settle on my cruise speed of 35kph to 40kph. For the next 5km, the lycra stuck to me like glue dangerously drafting me. Enough was enough. Hit the boost button and took the bike to its top sustainable speed on flat ground of just over 50kph for a few km. That soon solved the drafting problem and i settled back to my nice economical cruise speed again.

Single track is where I am really loving this bike though and getting far more confident on the technical and fast flowing stuff. The bike handles great and has excellent stopping power with the Shimano XT Hydros gripping 203mm rotors front and back.

Only other addition is a dropper seatpost so I can quickly set seat height on the fly to suit the type of riding being done.

Over all, very happy with the bike and its dual configuration capabilities.
 
Thanks Voicecoils. Yes, always use PAS mode on road and off road. Off road I like to keep the PAS low otherwise you tend to get pushed when you don't want to. I use button just to boost when needed and use the deadband in the gear shifter to activate the power cut through the micro if I am being pushed when I don't want to be pushed. Takes a bit of getting use to but works really well.
 
Yesterday I made a slight mistake charging the pack at my office and charged to 63V. This is normally fine for a 15S LiPo pack but the Bafang controller has an overvoltage protection safety that stops the drive operating at a voltages over 61.5V. So I was stuck with a 30km commute home unassisted. No problems. Locked out the suspension front and back and headed off. Bike felt great and although I wasn't keeping up with the road bikers, my cruise speed was more than acceptable. Quite enjoyed the ride home actually and pleased to prove the bike's ability as an effective commuter even without assist.
 
Well done! (as always). Brilliant fitting of the slim battery onto an FS frame. The motor/battery is visible when someone looks, but...even from just a short distance away, it doesn't really scream "ELECTRIC"...
 
HI Kepler.
Your build is hitting all the big ticket items I want from bike.
1. Mid drive
2. Dual suspension
3. Easily modified into high performing offroad and road riding,
4. Remains stealthy
5. Hydraulic Disc
6. Maintaining 40km/h speeds ( I commute to Melbourne city centre from 38kms out to the east) any slower and the commute takes too much of the day.
5. ....and you have retained all the qualities of a push bike (manual powered), exemplified in your recent ride home 30kms without power.

Kudos to you Bro. I believe you are hitting the sweet spot now. I used to joke to myself about having a full disc wheel set for off road and one for road. But you are living the dream!

I am curious. Does that bashplate double as heat sink. Or no longer necessary cos you tuned down amp ( i noted your previous intention of combining heatsink and battery compartment).

I know nothing about electric bikes...but I it appears you are taking advantage of the tech from both worlds (electric and traditional biking) mashing it together and STILL making sure it fits through the FUN filter.
Been lurking this forum since Feb. My BBS02 arrives when Paul EM3 gets the updated one. Still deciding final frame to fit kit to.
Hope to see you on the trails
JIM
 
Thanks Beemo. I am loving the dual role of this setup.

My bash plate doesn't act much of heatsink as its contact patch with the motor is quite small. With the max power turned down and the fact that I rarely use the drive at max throttle means the motor hardly gets warm anyway. Wouldn't be hard to design a bash plate that does act as a heat sink though and definitely worth doing if the plan was to push the drive hard. Of course pushing the drive hard and using a small battery doesn't really go together so for me its not a design consideration at this stage anyway.
 
Lovely work Kepler...

great bike indeed.
 
BTW. Despite your clever electrical engineering solutions it might be the design of that better battery case that you become known for. :) I like how you quietly hid the battery in an unassuming bag on the handle bars on previous setups. At first the position looks awkward, but then you realize the bag is invisible from behind. This new case reminds me of the dude from the inventors (the TV show) Emotion (I meant elation back in 2009 2010) mid drive. He had batteries in an elongated case like this but the material was neoprene wet suit material. Surprisingly stealth looking.
 
Beautiful Build !

Somehow I ended up with the same vision but without seeing your posts, just got a sweet deal on the Camber 29er 2013 I think with red accents and have a 500/750w bafang motor brand new waiting to be installed in something.

Like you I've noticed the serious issue with chainline after install of a Bafang but instead of milling the BB housing 4MM (I suppose you can use a threaded spacer to get it back if need be) I am using 4mm chainring bolts and a custom chainring adapter to inset it by about the same amount as you to help with the chainline.

Although I've not yet bought my road rims yet, I got the tires and figured I have a local shop build me up the wheelsetan for permanent road with something very light weight... The bike isn't heavy but I prefer to save weight were I can and it's safe. There will be a carbon fiber fitting today of seat post, composite seat, handlebar, adjustable stem but in carbon fiber and some other bits I've had custom made to save a few where possible - like the disk brake caliper spacers/mounts, etc.

I do think I will mask off the red accents on mine and go with either your blue or perhaps something darker, customized but not obvious... Mechanicals and electronics first.

Because 8AH isn't sufficient power pack for real commutes I will be installing a topeak mini clampon rack with mini Panier supports - this will hold 12S2P or 10AH and perhaps even 12S3P in just the trunk alone - forget the paniers.

I also want to make a clamp on (from the front) hard mount luggage or baggage truss (like a dahon or tern have) to the stem of the frame, this would allow adding up to 20 lbs frame weight but evenly dispersed.

I've got to say, in my brief riding this bike as a bike I have thoroughly enjoyed it!

Can't wait to see what you end up with Kepler!

-Mike
 
Nice build, Kepler. I'm planning a similar build on a Cannondale Prophet once I can get my hands on a new 750W drive.

Would you mind posting some photos/details about the bash guard? I was thinking of something similar for my build and would be curious about materials, attachment methods etc.

Well done.
 
Nicely done.

I am curious in regards to the Bafang. Does it have much drag unpowered?

The idea suits me much more than a hub drive. Any video in operation?
 
Thanks to everyone for the kind comments on the build.

mwkeefer said:
Somehow I ended up with the same vision but without seeing your posts, just got a sweet deal on the Camber 29er 2013 I think with red accents and have a 500/750w bafang motor brand new waiting to be installed in something.

Great minds think alike :). The camber really is a nice bike. Pedals well enough for commuting duties and at the same time is a very capable XC platform.

With the way I ride the battery range is adequate and covers my 30km commute with about 20% to spare. Not that fond of the 15S setup though as you loose LVC protection through the controller. Unfortunately the highest LVC you can program in the controller is 44V. 12S2P (10ah) I think is the sweet spot on this drive.

Cowardlyduck said:
How do you find the mid drive noise? Are these new models any quieter now?

These drives are amazingly quite and one there best attributes. As quite as DD hub

amigafan2003 said:
Hey Kepler - did you get anywhere with your "under down tube" battery mounting?

I ended up shelving that project. The battery enclosure ended up too close to the front wheel in most installations.

joshseitz said:
Would you mind posting some photos/details about the bash guard? I was thinking of something similar for my build and would be curious about materials, attachment methods etc.

The bash plate is a curved aluminium extrusion I picked up from my local aluminium supplier. Not sure if it was a special order item but it worked out to be perfect for the application. I will get some better photos of it. Attachment method is just with a heavy duty cable tie with the extrusion being held firmly against the frame and the lower section of the drive.

Fastest1 said:
I am curious in regards to the Bafang. Does it have much drag unpowered?

The idea suits me much more than a hub drive. Any video in operation?
The drag is unnoticeable when pedalling un powered. The drive has a sprage clutch on the internal intermediate reduction so the actual motor is fully decoupled. Sorry no Video. Would be pretty boring anyway as there is no noise so it would just look like and sounds like a normal bike.

AustinP said:
Hi Kepler, what sort of efficiency (wh/km) do you get with the on-road setup at normal cruising speeds?

Between 6Whrs/km and 10whrs/km. under my normal cruising speeds (35kph to 40kph)
 
Keplar, I love clean neat well thought out builds with some innovation thrown in too,,and yours are always there with the best of them! We all like to use our bikes for multi purpose but yours with the wheel change does away with all the compromise. Excellent plan brilliantly executed!!
 
deffx said:
Hey Kepler

Great bike,

I'd like to know your opinion, is the bbso2 the best commuter/trail friendly set up you've had, or was the bpm geared motor better?

thx
deffx, take my bbs02 on the Iron Horse for a spin if you like, Jesse has it at the moment
 
cwah said:
Aaah no quick release or lock for the battery?

The Velcro straps provide quick release. The pack is off in 15 seconds. No lock but the mounting system is surprisingly secure.
 
deffx said:
Hey Kepler

Great bike,

I'd like to know your opinion, is the bbso2 the best commuter/trail friendly set up you've had, or was the bpm geared motor better?

thx

Yes it is best trail friendly setup I have used. It works best if you are prepared to work with the drive as opposed to the BPM that can drag you around the tracks if that what you prefer. The balance of the mid drive is to hard to beat especially on the more technical tracks.
 
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