Specialized big hit MXUS 3k turbo

Cortnzs1

10 µW
Joined
Oct 9, 2019
Messages
5
Location
France (Savoie)
Hi !
I wanted to show you my built ! A big electric bike made from a Specialized big Hit
Electrized with a MXUS 3K turbo, sabvoton 72150 and 20s8p battery (vtc5a cells)

here is the bike
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I bought theses wheels, 19" bike rims mounted on a MXUS 3k turbo (4T) and the same on a bicycle hub for the front. With shinko 2.75" tires.

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the first step was to disassemble the bike and remove all the actual paint :

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here is an assembly test :mrgreen:

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First problem, the actual frame dropout will not handle the motor torque nicely.

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The second is there's no clearance between the motor and the actual caliper.

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maybe it will be ok with a 5mm spacer...

The cleanest solution is to rebuilt the frame dropout. It will be stronger, more reliable, and no need for torque arms :D

First try with a 3d printed part

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Second with a 6082 T6 aluminum part machined on a homemade CNC drill (a friend of mine made it)

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With the magura MT5 caliper

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And then I had to machine the bearings housings on both sides of the parts

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A bit of sanding

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Add the derailleur fitting to the part

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after some big welds

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with the rear wheel mounted

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Now we're good !

Next big step, the battery and controller housing. All parts were 3d designed and laser cut in 5754 aluminum sheets (3mm thick).

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Now we have to assemble this on the frame...

make some space by removing some useless thing... :lol:

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Tig weld the first parts

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and the rest

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Now the battery assembly ! It's a custom 20s 8P pack made with vtc5a cells

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removing the olds spotwelds marks

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Assembly test with the sabvoton and the 150A BMS

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Ok that's tight but it fits :bigthumb:

finish all welds

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and new assembly test

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and with the 2mm side covers

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So coooool 8)

magura MT5 fitting test ok

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Now the frame is finished ! Battery time

spot weld with the homemade microwave spotwelder
I used some wide nickel sheets

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wiring for the BMS

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some adhesive tape

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and PVC Heat Shrink Wrap

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Battery is finished !
Time to put it into the frame :D

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Wiring wiring and wiring...

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Charger plug

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power button

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and after some more wiring stuff... first test !

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First impression, it's very powerful, a lot of torque a lot of fun 8)

But it can't stay like this. It needs some paint

new disassemble and prepare it to receive it's new color

epoxy primer

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Dacia duster color (CNA)

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and then I used a stencil to paint the design on the rear frame and side covers

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the final coat, the varnish

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final result exactly like I wanted :D

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and after some burnouts in the garden :lol:

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That's all, I don't have more pictures
The bike has now some months of trying, and kilometers, some wires issues but still works fine without surprises

Hope you enjoyed read it :wink:
 
Wow great build, heck of a Big Kahuna single post!



Cortnzs1 said:
wheels, 19" bike rims mounted on a MXUS 3k turbo (4T) and the same on a bicycle hub for the front. With shinko 2.75" tires.

IMG-8284.jpg
What did you end up with as total O.D.? Could you have gone to fatter?



 
Wow so its really weird that i saw this post , as myself am about to do the same big hit and looks like same motor but I went woth thr sabvaton 7220 .
 
I was trying to semd you a few picks of mine but i dunno how to upload em .
Hey perhaps would you consider helping me with mine maybe
 
Thanks ! :D

john61ct said:
What did you end up with as total O.D.? Could you have gone to fatter?

Sorry I don't remember the exact oustide diameter, but it's a bit smaller than a 26" bicycle wheel. I think that's the perfect dimension for this bike.

Jeffharris said:
Wow so its really weird that i saw this post , as myself am about to do the same big hit and looks like same motor but I went woth thr sabvaton 7220.

You are building an electric specialized big hit too ? awesome ! Please share some pictures by uploading them on an image host and put the url between like this
Capture.png

You can use https://imgbb.com/ for example
 
GREAT and Amazing Built

Need some Fenders to keep the dirt off...!! :lol:
 
Beautiful Big hit build!

I enjoyed my big hit frame a lot both in pedal form and ebike form.

What keeps the pack from bouncing around inside the frame cavity?
 
Hi ! thanks !

I only tried the big hit on ebike form, I think it's a good way to recycle an old DH. the frame is very strong and handle the electric motor's torque gently.

The battery is adjusted inside the frame and there are some foam between aluminum and the battery to prevent friction.
 
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