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bmc trail fox with puma hub motor

Nice stealth build. I think it can be just as difficult to build stealth as it is to build a high powered monster so congratulations on mission accomplished.

I must admit l get a lot of satisfaction riding a fast Ebike that the majority of people you pass just think is just a normal bike. :twisted:
thanks. i still i could make the battery disappear ... somehow :)

when making a break ppl come by and ask: so this is electric? how fast? how far? how much? and i just grin *ggg*

best way to sell ebikes: pass some middle age guy (no lycras of course they hate us) trying to reach the top of the hill with at least 20km/h difference, than stop at the top and pretend playing with your phone or something. the guy stops and will start talking. that's the point to make an easy deal :)

btw: i admire your sets. they just look really great. if i had a street cycle i'd buy one!
Izeman, I was thinking of using a similar Topeak saddle bag as you originally had on this bike. Though I was going to use the one with a mesh drink bottle pocket on the back to fit the controller in.
I was wondering why you moved away from this design? Did it make the bike too top heavy?
My other option is to use the small Revelate Designs Tangle Frame Bag for the battery which I assume would give the bike better balance (fits in the triangle) but this poses a problem regarding stealthy location of the controller.
funny you asked, as i returned to that battery bag last week :)
the triangle bag did not stand the stress and broke. it was a perfect fit, and could be removed completely quite easily, but i was not that strong.
now i installed the topeak bag again. top weight is not that much of a problem, but you have to take care not to do wheelies while riding over bumps at high speed. the front wheel lift quite fast.
and after all i do like the look of it with one disadvantage: if you want to make it look stealth you have to hide all cables and connectors in the bag, but than it's a real pita to remove the whole bag. takes 10min to unplug all plugs and route them through the little holes in the bag.
Hey Izeman,

I am actually wanting to build a very similar bike to this. What are your thoughts about the mac 12t? If you could change anything about the controller or motor or battery choice what would it be? For example more fets, volts etc...

I am gradually planning a slow hill climbing bike as stealthy as possible.
i think it's perfect as is. with 12s lipo it does around 25mph or 45km/h. this is ok. maybe a bit too slow for the streets but a bit too fast for the woods. it is possible to bring the motor to a stall on a steep climb. but MUCH better then any DD at 3x the power.
if i could add more Ah w/o making the battery bigger then i would. 10Ah gives me around 15km in the woods. can be more when riding with modest power on the road.
9fet controller is perfect for 1500W.
thanks, but that sounds too fast still... I would go to 20" to slow it down but I am concerned about roots and log clearance. Only other option is 24" wheels, still pretty fast.

Is there another way to make this more efficient at lower speeds? Or is there a slower motor out there?

crossbreak said:
nice BMS mod! what current limit did you set? I run 65amps and it gets pretty hot even with heatsink
to be honest i dropped this bms. i only had troubles with them. i have 4 of them in my spare parts box. they just stopped working w/o any obvious reason. current never was more than 40a.
izeman said:
update on torque arms. did drawing in autocad and sent the .dxf to a nice guy who did laser cutting of stainless steel for $30 for all four :)

on the picture it looks a bit strange because of the grinding. but it all looks nice when you turn them a bit.
the open arms go on the inside directly to the frame, and on top of them there will be the closed type.


i soldered the two arms together so it's easier to install. i did polish them with grade 400 sand paper to look nicer. they really shine *ggg*

Hi, I like your torque arms. I am also planning to custom made my torque arms for my next ebike project. How did you get the dimensions to prepare your autocad? It is very difficult to measure accurately where the axle hole should be in relation to the two mounting holes. Will there be some standards for that?
ooops. let me think ... this build was abandoned almost 2 years ago. i just wanted to have my expensive BMC back for "real" mountain biking and needed the MAC for my mid-drive conversion.
the controller has an anti-spark unit installed. as you can see here:


but this is TOO weak. only one 3077 for 30A is getting hot, and w/o heat sink this doesn't work long. today i use 2 in parallel on a heat sink and they work up to 50A, but still get really warm.
the switch (the red one mounted back on top of the battery bag) only opens and closes the gate circuit. so there is no load on it. only mA.

i recommend reading this thread: https://endless-sphere.com/forums/viewtopic.php?f=3&t=40142. there's all you need to know about pre-charge switches, how they work, and what they can do and what not.
Ah Thank you.

I bought this controller to go with my 6t mxus


But I can not tell if it has an on/off switch.

So I got a circuit breaker for solar system

Midnite Solar MNEPV 150 VDC 100A Solar Array Breakers

Do you think it will be safe using it as a on/off switch as well?
From my understanding the breaker contact will degrade over time if its tripped.
So if I used it as an on/off wouldn't that be the same as it tripping?

Thanks Simon
it has an on/off switch. but it has nothing to do with anti spark. it just turns the controller on and off.
BUT the spark happens when you connect the controller to the battery. there are big caps connecting + and - in the controller, and they are charged in a blink of an eye. this causes high current to flow which makes the spark. it doesn't matter if the controller's electronics are turned on or off.
and this spark burns the contacts of the connectors.
so a house hold breaker will wear. it will spark but you won't see the spark. maybe hear them. there are breakers that are made to withstand that torture for some time. but don't ask me what the are called or look like. search the forum for it. you'll find them.
try the breaker and see how (long) it works. it's the most simple solution.
if you know how to solder build an anti spark.
or get those xt90 connectors with build in anti spark resistor at hobby king. they are know to work very well.