KONA Entourage Build Thread - middrive (pic heavy)

[izeman]

inspired by crossbreaks' mac/bafang mid drive conversion, i know want to make on as well. i have a mac in the rear wheel of my bmc trail fox, which will be converted to mid drive, and may be installed in a kona entourage.
this bike is available with a really high discount at the moment, and has decent components installed. some good, some heavy, but overall quite nice.
i don't want to have the motor in front of the bb, but behind the bb. this give imho more stability of the frame.
problem: the entourage's rear wheel almost touches the bb. so i will need to make new cross-ties between bb and rear axle, and rear axle and bar which moves the rear damper. those will be made out of steel instead of aluminium as i feel safer that way.

i know the bike will not be as lively as before, but it's NOT meant to do freeriding or downhilling. just a nice bashing through the woods

battery could be 8x 6s 5800 zippy or 8000 or a mix between, connected as 12s4p, so 48v and something between 23-32Ah equals around 1kWh of energy. motor should be around 1.5kW with a 9gear cassette in the rear (14-42 teeth) giving a perfect gearing for 18km/h full speed in lowest gear and 55km/h in highest gear.

this is a first rough sketch:

 

[izeman]

Here is a link to an article on this wonderful custom E-bike.

http://www.electricbike.com/hannes-crossbreak-style-mid-drive/

 

[izeman]

this is the current state of the finished bike:

 

[Whiplash]

It could be the pic but it looks to me like the stretched rear half will cause geometry problems with the lever arm that goes to the shock. I seems like it will take away too much angle from that pivot..

 

[izeman]

you're right. now i see this as well. i also didn't take the up-movement of the motor into consideration when the suspension works. the motor will need some space to move and not hit the central vertical tube.
any idea how to solve the 'angle' problem?

 

[crossbreak]

just elongating the swing arm would keep suspension geometry

 

[izeman]

yes. that's doable. but now i think i got a problem with the chainline as well. it's hard to imagine if the chain would hit the swingarm or not.

 

[andrenoites]

Why complicate when you can ride it like this:



Looks good to me

No need to buy the expensive ego kit, just get a Cyclone 1680W with a BB mount and you are ready to go:

 

[izeman]

i need the challenge
my next build needs to look like the bike was planned to look that way. not just installing a kit, but build something more unique. and as i want to install the batteries in the frame, i have to cut it and weld a box anyway. so why not gomthe whole way?

 

[AussieJester]

Look for dustyearlobe builds...he installs mid mounts in the box section of the frame
Much better way go than your planned route imho

KiM

 

[andrenoites]

i need the challenge
my next build needs to look like the bike was planned to look that way. not just installing a kit, but build something more unique. and as i want to install the batteries in the frame, i have to cut it and weld a box anyway. so why not gomthe whole way?

I understand that

Well, it's your idea. If you really want it go ahead

We will back you up because we love to see new projects like this one

 

[izeman]

Look for dustyearlobe builds...he installs mid mounts in the box section of the frame
Much better way go than your planned route imho

i know that there my be better places for the motor - like mounting them IN the frame triangle or in front of the BB. but most FR or DH frames have the damper in the location where you want to place the motor, so this is a no go. and i don't want to have it in front of the bb as well, as the mac motor is quite large and i would hit the front wheel or the ground - or both.
so maybe the bike rides weird with 12cm more wheelbase, but we will see. 1300.- for the complete bike is not a lot of money and it will be fun building it.
another issue i have, is that the frame is available in S only, but i'm 1,90+ so i would need a L frame. i just checked all differences, and because i will cut the frame in half anyway there should be no problem making it larger to fit my size.

 

[TorEddy]

If you're gonna cut the bike to pieces anyway, why not try something like this?


I think extending seat and chainstay will give you much work and a bad bike.

 

[izeman]

good idea. this is the other possible way, but i'm not sure if i will have enough room there, as the motor is bigger than you draw it. if it was this small it would be ok. with the motor in this position it will get some serious chain troubles i guess

 

[TorEddy]

I think a bigger motor only would give less battery compartment.
I dont see any chain problems as the motor to crank is one chain, and crank to back wheel is another.
Standard mid-drive setup.

 

[izeman]

i just did some sketching, and it looks like the perfect solution. the chain seems to just pass the bb - maybe a little roller is needed on the lower side of the bb.
battery box could handle 8x 8000mah 6s lipo which is nice. not too much, but ok.
do you think the motor could be made a structural part of the frame? atm there is NO connection between the battery box and the bb. could be a bit wobbly *ggg*

 

[crossbreak]

simply build a box around the motor it do the same... just the heat sink overlaps the mudguard

 

[izeman]

i see some significant differences between the two setups. you did NOT cut the lower tube. i remove it and replace it with the battery box. so a little box covering the motor will not stand the forces in the frame. but maybe i didn't understand your idea.

one more question: could you please tell me the width of the motor EXcluding the heatsink? would it fit between the pedals? from you model i can't judge if it fits inbetween. i know this is the bafang, but the mac should be similar width.

btw: i really envy your CAD knowledge. i really would love to be able to do the same. sketching with pencil and ruler is nice, but not very precise and definetly NOT 3d

 

[crossbreak]

i thought that your concern was that the motor wont get proper heat sinking when enclosed...

you could fasten your new downtube box on the BB by the original threads and the standard HT2 cups and glue it to the head tube using scotchweld. Also add scotchweld at the BB side additionally...your connecting surfaces should be machined so that it is a tight fit. if you make your box from AL7075, you can even glue it together with scotchweld :lol: i like this sh#t Then just put your motor into the box.... of course there must be a round hole in the left side that takes the heatsink. If your box is fromm alloy, you dont even need a whole... you could just bolt on the heatsink to the box approximately where you motor is thermally connected to it.... even better...use the complete left side as a heatsink by just machining 6mm deep slots into a ~8mm thick AL7075 plate

BTW your and cal3ks 14mm freewheel adapter are ready, but I ran out of IGH sprocket hubs... new ones will arrive in 1-2weeks. then i can ship... no idea if your money has arrived, i'll have a look on my account tomorrow

 

[crossbreak]

i don't want to have it in front of the bb as well, as the mac motor is quite large and i would hit the front wheel or the ground - or both.

this fear is completely unnecessary if you have a straight downtube.... I hit the ground several times with my converted SWXB (not much smaller than the BPM/MAC)... it was always the chainring that touched the ground.

Of course, if you buy a bike with bended downtube and want to make it straight again, you got your challenge :lol:

 

[izeman]

damn. 8x 8000mah is a BIT too much maybe i was hoping for a really big battery. but 8000mah packs are so much bigger than 5000 packs. and i want to fit the bms inside the box as well. 32Ah would mean ~60km range at wot. 20Ah is not that much

building a bike that has a clean look and no wires/cables visible is a tough job *ggg*

 

[madin88]

izeman, nice middrive projekt
how much is this frame and where to buy?
any updates on your mac conversion? I'm excited to see how you realize this conversion.

I'm also thinking of converting a mountainbike to a middrive for a friend, but first i have to learn more about mid drives. What do you say to a cyclone 1680W unit?

 

[izeman]

the frame is €1.345.- plus 25.- shipping. i ordered it during a -10% sale, so it was ~1.200.- which is quite nice. only problem: they have only small ones left. not a real problem for me, as i will cut the frame anyway and can stretch it 10cm - which makes it a large frame. should fit me, as i'm 192cm.
the motor is more or less done. i posted some results in crosswheels conversion thread, but will post something here as well. it's a bit noisy, but i think this can not be avoided.
cyclone may be the second best choice and MUCH easier to install then a motor that was never designed to be used that way.
i ordered one set for a friend, and we'll see how it fit's his downhill bike.

 

[madin88]

cyclone may be the second best choice and MUCH easier to install then a motor that was never designed to be used that way.
i ordered one set for a friend, and we'll see how it fit's his downhill bike.

please let me know how it performs if you got it installed. I think your MAC conversion will perform better, but it is a lot more work.
i stay tuned

 

[izeman]

the motor conversion is now done. though i'm not 100% satified. the is some vibration when the axle turns. and e-motors normally run w/o any vibration at all. so there most be some bearings not sitting perfectly or something rubbing inside. will be hard to find out.

here is a short video of the motor running, drawing 3a @45v so around 130w loss at wot. i installed a little magnet to get a speed signal and you see 45km/h max. due to the reduction of 6:1 instead of 5:1 this seems fine. no load speed was 55km/h before.

[youtube]c0_y50EIg5A[/youtube]

here is the load of lipo that arrived 2 days ago. it's all tested now to match the packs correctly and to see that there are no dead cells.