Old Trusty- budget beater

Most of my bikes are high dollar stuff, especially since my stint working for a bike shop that tainted me with low cost parts. I have realized that the end goal of my ebikes really boils down to cheap and reliable transportation. With the find of a $20 bike at a yardsale, I got just the right start to a cheap build (with exception of batteries).

Parts list:
Fuji mountain bike from yardsale
9c motor from ebikekit
12 fet infineon controller
thumb throttle
scrap steel for torque arm
m10 screws and nuts
hobbycity lipo
some sort of BMS system in the future


So on Saturday I got to work. I hate typical torque arms, so I decided to just weld something onto the frame that should keep the wheel in place on 18s 45a. Pics will show the work. The welds look a bit cold and I wasn't doing so good keeping my hand steady, but they should hold just fine. I was more afraid of burning through the tubes than of getting cold lapping. FYI, don't hit the braze filler with your tig arc, it will ruin the tip fast.

Another awesome dropout.. did you TIG it? Gotta love the $20 finds, some of them frames are fancy metal, nobody cares though once its old.

I migged it to tack it in place, then went back with the tig to fill it in. I just have flux core in the mig currently or I would have used it for the whole job, tis a lot easier than trying to keep a steady hand with the tig.

I kinda sorta got the idea from John in CR's dropouts. I figured a good pinching would do the trick!

I have no qualms welding on a nice frame, especially when it is steel or cromo. I just may put some plates on the back so I can put pegs on it too :lol:

johnrobholmes said:

I migged it to tack it in place, then went back with the tig to fill it in. I just have flux core in the mig currently or I would have used it for the whole job, tis a lot easier than trying to keep a steady hand with the tig.

I kinda sorta got the idea from John in CR's dropouts. I figured a good pinching would do the trick!

I have no qualms welding on a nice frame, especially when it is steel or cromo. I just may put some plates on the back so I can put pegs on it too :lol:

Click to expand...

That's my favorite thing about the forum. We share ideas and others adapt and improve them. Soon the kit makers will have to comply, and spun axles will become a thing of the past for all to benefit.

You can betcha that my first full built frame will have pinching dropouts integrated. I HATE torque arms, and a 1/2" thick dropout is stout enough and won't be much weight penalty. Add in a pinch bolt for securing and I think we have a winner!

Cool build! I'm looking forward to seeing how it performs compared to mine, as you are using the same electronics I used on my bike.

Your dropouts are awesome too! Quite a nifty idea!

johnrobholmes said:

I have no qualms welding on a nice frame, especially when it is steel or cromo.

Click to expand...

I'm with you, I wouldn't either on a $20 find! I just mean if you are patient and dig around.. you can find some pretty fancy tubesets on some of those cheap old steel frame bikes. Some of these finds were $400 to $800 bikes back in the day.

Got some more progress last night, and will be trying a few mounting schemes today. I am thinking about a rigid bolt-on mount for the packs, and then a frame bag to act as a safety catch and stealth cover.

I swapped out the 9c motor for a bafang, and boy did it make a difference in the weight! Right now I am running a sensorless Xie Cheng (keywin built, Shenzen Sucteam) on 36v LiFe. With the 36v 20a controller I get all kinds of runtime on the 10ah pack, I did a range test and am waiting for the recharge verdict.

I am also having some troubles with the rear axle popping out of the dropouts when I stand on the pedals hard. Never had the issue with QR axles, and I am surely tightening down these axles snug. Not sure what to do about it, other than use the motor more than my legs on hills, or maybe make another axle retention device.

All in all, this bike has been the perfect slow commuter solution for a quick and cheap build. It gets me to town and back with plenty of fooling around time. When I am not quite fresh enough to pedal around all night, but when I want to be on a pedal bike, this is the perfect ticket. Except for the damn uncomfortable seat.

So it ran fine on 18S 45a on a 9C but piddley little bafang is pulling free from the dropouts ?? That's strange indeed!
No sign of movement or distortion in your axle mounts ?
Are they the same on both sides or just 1 ?

johnrobholmes said:

When I am not quite fresh enough to pedal around all night, but when I want to be on a pedal bike, this is the perfect ticket

Click to expand...

I hear you there, I see a build in my near future that will be a little rear bafang with a 6 fet controller and a 5ah 12S lipo pack to offer a bit of pedal assistance. Twisting the throttle and not having to worry about front wheel fighting to come might make me complacent when I get back on my other bike though... :lol:

It is my pedal force that yanks it from the dropout, not the motor force. It just pulls out on the drive side.

My GF took it for a spin last night and it took some convincing to get her to just grab full throttle. She is used to my other bikes that are a little more wheelie prone :lol: This thing is like a gentle breeze 8)

So it looks like I will have about a 20 mile range on the 12s 10ah Life pack.

This bike has been a dream for lower speed operations. I really like that I can plug in my 36v lead acid bulk charger and just top it off super simple. I really wish I had grabbed those a123 pouch cells when I had the chance. It would make my charging life a bunch easier on a few builds.


My GF wants to help me make a battery bag that will hang in the frame. She says if it looks good enough, she will let me convert her bike to electric too... I do happen to have a few extra hubs just "laying around". She says she is afraid of getting too used to the electric assist. I tell her that riding an electric bike sometimes is better than never riding a normal bike. She agrees 8)

Pics when we get the frame bag made.

Two year update, going strong! I swapped in a Puma motor to give more ooomph and upped the voltage to 20s lipo

Ran great for months and months until I stood on the pedals in a low gear and sheared the drive side bearing support/ freewheel mount. Now the hub is wobbly I reckon I will hack off the rear of the frame and convert it to a longtail with horizontal pinching dropouts if I ever get some free time. I'm starting an electric bike biz in town around October and will have some extra hands to do my dirty work for me and help finish up a few dangling projects

Updates! Put the batteries in a frame bag, laced up some new wheels, bmx bars on front, and a little geared motor on front. It is by far the best handling ebike I have ridden, the balance is very nice and I can bunnyhop curbs with no big effort. I really like the Fat Frank tires, they are plush and squishy for the hard tail. I wouldn't recommend riding them too hard as pinch flats would be more common than a park/ street tire like the hookworm. Great for commuting though, I've been riding it to and from work at least 3 times a week.

Sorry about the cluttered pic.




I also made a little panel for some display lights and switches. Of course as soon as I finished it I wanted a few more options, so I'll cut another soon.

Speed indicator lights and a switch for high and low beam headlights and tail light system. I'll add in a trim pot for the throttle, a switch to chose between amp and speed controlled throttle, and tighten everything up a bit to get it away from my knees. I also will be making a CA mount and headlight mount when I get some spare time. If anybody wants something similar made just let me know, I would estimate about $25 of materials and machine time for fiberglass and $40 for carbon fiber. I'm moving my CNC to the shop this week and we are going to start making more Ebike related products such as this one.

Here is a better shot of the panel. It is made from G10 fiberglass.

You can't have too many cool switches

Sent using Endless-Sphere Mobile app