Downhill MTB build. "The Beast" (lots n lots of photos)

[Andrew]

I have done a number of builds over the past two years, mainly swapping frames, motors, battery positioning and even dual drives.

Here are some photos...

This is how it all started...








Dual pie,   Is was a bit of a bad boy!


Nice fat tyres..


Dnp 11T freewheel and 48T chain wheel needed.



Dual mini motors.  A nice 'civilised' ride. I was lucky enough to get a bespoke battery pack made by a friend and forum member Dirtyginge, aka Paul. I was never happy with a rear mounted pack.


Don't ask me how I wired it, but I did!


My wifes front wheel mini motor build..


The 'tron' bike.  I used a steel frame with horizontal dropouts.  I highly recommend these frames for a hard tail mtb build.  Bendable steel for squeezing in rear axles and slot dropouts for piece of mind.


Bespoke made to measure frame bags to maximise battery capacity. I have had a 84v 10ah li-ion pack in this bag along with a contoller.


This hardtailed steel frame has been a favourite of mine for recent off roading...

[Andrew]

Anyway,  here are some photos of the new full suspension downhill bike.

[Andrew]

Commencal meta 6 frame



Rockshox domain dual crown fork.



Beginning the build


The frame comes with 12mm through axle dropouts, shame that a motor axle will just spin freely with these. I am sure you can get 10 mm ones which could be filed out to a 12 or 14 mm curve for a hub motor.


I went for vertical dropouts which are quite deep, though realistically I will ned a torque arm. I had to do a little filing for a tight fit.




A rear motor in place, it is not a GM motor(please forgive me)' but it was a good bang for the buck solution for now.


I can foresee problems with chain slap


This is where I left things yesterday evening....



Lots still to do.

[MAGICPIE3FOCUSPOWER]

Hi thanks for sharing yiour builds!
Good jobs mate!

What type of motor is your latest build?

[Andrew]

Hi,  the motor is a Bafang BPM 500w 48v geared free wheeling motor.

They are relatively inexpensive to purchase and get delivered from China to the UK so I thought I would give it a go. How long it will last off-roading is anyones guess. I should really have a direct drive motor for this purpose which off course has no moving parts.  I would like to try a mini pie IF they did them without built in controllers. It would be good to see how much wattage you could put through them. 48v and 25to30amp would be worth a go.

[MAGICPIE3FOCUSPOWER]

Aaha nice motor!
Looks fits well in your nice bike.

But no torque arm for this setup?

[Andrew]

I will figure out a torque arm as the build develops. Had no time today, and my wife is full term pregnant

[MAGICPIE3FOCUSPOWER]

Aaha nice I am curious...

And congrat...with your....wife

[GM Canada]

I will figure out a torque arm as the build develops. Had no time today, and my wife is full term pregnant

Wife? I thought Sarah was your girl friend. Did I miss the wedding? Umm it is still Sarah right?

Congratulations Andrew! Is this your first? May you be blessed with a boy and a girl like I am.

One thing to remember is something I was told when my first one was still crawling. "You cant wait until they can walk, You cant wait until they can talk. Then only a few short years later you can wait until they sit down and shut up!" Oh how true that is! Thank god for ipods, xboxes and computers to keep them quiet!

Now I understand why you were missing from the forum since march. You have been busy

Take care and I hope delivery goes well!

Gary

[Andrew]

You are correct Gary, we are now husband and wife. It was a planned mad week in Las vegas back in April that turned me into a married man and a father to be!  It is crazy to think what consequences there can be from too much of a good time

Every time Sarah now has a twinge my blood pressure rises with anticipation.

[MAGICPIE3FOCUSPOWER]

How fast is your Dual Pie 3?
What voltage is it eating?

[GM Canada]

Well I certainly wish you and Sarah the best!

I was looking at the dropout on the new bike. They look pretty meaty. I don't really see a need for a torque arm with dropouts like that and a 500 watt motor.

Gary

[Andrew]

How fast is your Dual Pie 3?
What voltage is it eating?

I no longer have a dual pies running. I sold one of the motors. They were version 2 pies with internal controllers so I was a little restricted by how many amps I could put through the motors. Probably only 18-20 amps with a48v GM pack. So only about 1000w.  The torque was excellent but the bike was heavy when not being ridden.


I have run a single pie with an external controller with a 84v battery limited to just 25amps. It would pull over 1700w and did over 35mph.  The batteries would not give more than 25amps so not as fierce as I would have liked to be able to pop wheelies and scare ones self. Though 35mph was bordering on being unsafe....  Very unsafe lol!  A novelty that did not last long. Good fun in theory but not very practical on UK road surfaces or motoring laws.

[Andrew]

Well I certainly wish you and Sarah the best!

I was looking at the dropout on the new bike. They look pretty meaty. I don't really see a need for a torque arm with dropouts like that and a 500 watt motor.

Gary

A you say the dropouts are quite deep. I have a small trick up my sleeve instead of a torque arm.  I have a pair of bespoke made torque washers that I am going to file down to the exact shape and size of the dropout slot and wedge them in.
A you say 500w motor should be fine though it does pull a lot of amps. The motor is a very slow wind, 216bpm high torque.  I usually run it limited to 30amps on a 54/48v battery and see peaks of 1700w.........   So far so good but tome will tell.   It only does 18-20mph tops but lots of pull from a stand still, perfect for off road riding.

[Andrew]

A few more pics from todays tinkering.





Had to add some velcro on the frame bag to hang it on the top bar. Glued and sewn on, it wrecked my hands sewing through the material and velcro.


I have left the neck of the forks uncut at present so I can fit the cycle analyst in a central position. I have just a half twist throttle and a rear gear changer on the handle bars.


I may get it up and running tomorrow