build thread: klein mantra hs3540 5kW 70km/h 20" (done)

izeman

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Jun 21, 2011
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Vienna, Austria
hi all

now that my bmc mountainbike with mac hub motor is finished, it's time for a new project.
i saw some bmx style conversion, and thought i could use my beautiful klein mantra which i bought 15 years ago (and still looks like brand new - i took great care) and modify that. i'd like to do the following:

.) 9c 2805 hub motor in a 20" rim -> crystalyte 3540 and alienation delinquent rims
.) maxxis hookworm tires -> pirelli ml75
.) infineon eb312 controller -> check
.) ~20s1p a123 pouch cells -> 24s1p a123
.) peli case 1300 mounted under the handle bars -> too small -> chose explorer 2717 at the handlebar
.) disk brakes front (already installed) and rear -> avid elixir3 and 200mm disc
.) cycle analyst -> v3

what do you think?

this is the bike as it looks like now. i love the look, but it always was a bit too small/short for me, and riding in the hills made the front wheel lift all the time.

7227,fotoO5MFL.jpg


i'm still a bit woried how to mount torque plates/arms, as those dropouts look really thin and weak

7228,dropoutYEXLM.jpg


as i want to reach 40mi~60km/h i would have to feed it 2.5kw.

.) i'm also still unsure which kind of throttle to use. what do you prefer? half grip? thumb throttle?
.) should i use all 21 gears? or just the three front gears OR the seven in the back?

cheers izeman

update 20121214:

i bought a crystalyte 3840 and 12fet infineon controller.
i also switched from hookworms to pirelli ml75 2.75

update 20130201:

this is what it looks like now. found out that the controller is sensorless, so i ordered a new sensored.

IMG-20130201-00106.jpg


update 20130302:

frame welded

11_rahmen_alles_geschweisst.jpg


update 20130321:

ready to ride, at least for a test ride. frame still needs to be painted, and some other stuff is to be done

ready_to_test.jpg


hochzeit2.jpg


update 20130416:

almost done, some cosmetics to do, but it's done:

IMG_0088.JPG


update 20130527:

latest addition is a PAS, and a nice rear led light.

CIMG6438.JPG


bought a new fork. 120mm air/air. much better ride, and better looking as well

IMG_0057.JPG
 
If you have fitment/wheelie problems at bike speeds, it'll only get worse at higher speeds and you'll be regretting it after the conversion.. :(

It's a very cool bike, but i do advise you find another.
 
problems with frontwheel lifting are iminent at very steep hills with rocks blocking the way and stuff. on normal roads there is no problem.
the frame is not super small, it's just not perfect. and it's standing in the corner. and i think a second life would be fair :)

doc's plates are too big to install there. i would have to cut the dropout from the frame, and this is not what i want.
i will have to find a better solution.

the battery on to of the frame? i chose the pouch cells because they perfectly fit in the box. and in regards to center of gravity it's much better between the handle bars and the fork, don't you think? why would you place them there?
 
one more thing to add: it's more a project to work on. i don't think that i'm gonna ride the bike a lot - unfortunately.
you know when projects are finished i'm not intereted anymore. on the other hand: range of that bike would be 20mi+, so it's enough for going to the office, charge it there and go back home.
 
izeman said:
problems with frontwheel lifting are iminent at very steep hills with rocks blocking the way and stuff. on normal roads there is no problem.
the frame is not super small, it's just not perfect. and it's standing in the corner. and i think a second life would be fair :)

doc's plates are too big to install there. i would have to cut the dropout from the frame, and this is not what i want.
i will have to find a better solution.

the battery on to of the frame? i chose the pouch cells because they perfectly fit in the box. and in regards to center of gravity it's much better between the handle bars and the fork, don't you think? why would you place them there?


Maybe you can shave down Docs plates to fit. Can you post a better close up drop pic..

As for the battery placement, I dont think there is anything wrong with the idea of the Pelican case mounted out front on headtube, dont like the handlebar idea as much. Would certainly help with wheelie'ing & makes for an easy install.
Oatnet IIRC & others have proven its doable.
So is a Goat. Nothing wrong with goat, but I like Kitties.
Just dont believe it to be the best solution. The more weight you get centered the better.
Look @ 100 years of motorcycle development, & show the case where weight in that location has advantages to centered.
It basically doesn't exist.

I like the bike alot.
Unique ride to convert.
 
I will be fallowing this build. I have a retired Mantra in my basement that I am eye balling for a next
build. I see lots of challenges and it will be interesting to see how you work some of them out. I don't
find this bike that much of a wheelie machine. I have tens of thousands of woods miles on it and lots of
mods for my ride style however. Now the cinch-bugging, where the rear wheel feels like it wants to
come up over your shoulder on a hard stop, that's a very real thing. You just have to get use to it.
 
i chose that hydraulic disc brake. it's a proven brand, and are not over priced. for the price i'd like to take the shimano xt, but the avid has all hydraulic components on the outer side of the disc (not between the disc and the wheel), so they should fit the 9c motor - as this afaik only has a 16mm gap between disc and side cover plate.

21205,exlixir3A1XHP.jpg


edit: it now is the elixir3 not the exlixir1, and i will go for a cylte 3540. so no worries about gap for disc caliper.
 
Was the dremel stationary in a drill press?. If so you can make a fence and the cuts can be fairly precise. How are you going to attach the metal compression blocks to the board?
otherDoc
 
Unfortunately it was all freehand. But it's not so important to have all slots 100% accurate. I did another board where I took care to make the surfaces 7mm wide and the distance between them smaller. I will post a picture tomorrow.
There will be 2x6x45mm aluminum strands, drilled with 3 holes on top, and a 4x6x45mm steel one on the other side of the board with 3 threads. It will be a self made copy of Agniusms boards.
 
Seems a shame to put a heavy motor on such a light bike. I have dreamed of putting a friction drive on my specialized 24" bmx but I don't think anyone has perfected a commercial one yet.
 
yes. lightweight is gone after the conversion. but this bike is of no use if it starts rusting in the garage. so better convert it into something new. i can revert it to original state anytime. there will be no non-reversible modifications.
that's why i will weld a completly new rear frame. work on that may start within next month.
next step is the battery and lacing the wheels.
 
opened the crystalyte 3540 today. just to peek inside :)
i want to swap the 14awg for 12awg, and add a termistor to check stator temp with the newly ordered ca-v3 (thx to justin!)
i also checked the rubber seal, and there was not metal spring installed - maybe crystalyte improved their design.
 

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I converted a black and red Mantra last year. I can't find any pics but I am looking forward to see how you do this!
I used 48 volt 20ah Ping pack split in half: one half on top one on bottom and Nine cont rear hub. The older fox air shock need alot of PSI to handle that heavy of a battery.

The seat tube needed to be cut because it would bottom out on cross bar of seat stay. I used grin tech universal torque arms on both sides. looking back the dp420 doc dropouts would have been more appropriate with this bike.
 
my spokes from catsnapper arrived today, and the rims arrived just before christmas. so i could start lacing the wheel.
i started with the read wheel, as this is radially laced, and was quite easy.
13g spokes and washers.

first spokes in:

22048,img2012122700047I0E6T.jpg


all spokes in, but not centered:

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a valuable tool. bought it 2 years ago but never used it :)

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a special made bit. dremeled away two sides from the philips bit

22051,img2012122700053WF500.jpg


the pirelli ml75 slipped on quite easily. no pressure needed. a perfect fit

22057,img2012122700055IE6T7.jpg


BEEEEFYYYY :)

22058,img2012122700056NKK1N.jpg
 
torque plates (which will be clamped as well) are taking shape.
made of 10mm wide st52 they are quite strong. the little hole is to relieve stress from the cut which will be made between the 10mm slot and to hole - to make clamping possible. right now they are a super tight fit, almost too hard to insert the axle. ;)

22345,img18070RZ3H.jpg
 
I like how you laced the wheel, look really great !
 
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