Another "stealth bomber" build.

j bjork

1 MW
Aug 31, 2018
Linköping, Sweden
Alright, I have built a commuter before. But that is my experiance in e-bikes. I realized that this can be fun, but then it needs more power..

Well I guess it will not be much of a build, mostly bying parts and put together. But I am new to bikes, I have built some cars before. So I hope to get some help with what parts to get..

Well, for a start I bought a frame:


It is not as well built as I hoped for, most parts are only spotwelded. I could sand blast the whole thing and tig-weld all of it, but I think I will try it as it is for now..

Anyway, there was a serios issue with the bearings for the swing arm. It was delivered with a rubber bushing, but the previus owner had replaced it with ball berings. That seems to me like a better solution, but there was really nothing to keep the berings in place.

I thougt about getting the frame milled for bigger berings, and just the first 10mm or so, to keep them in place (and be able to use a bigger bolt). But I decided to use the berings but use my lathe to make some parts to keep them in place.


So I made a pipe to put between the berings, washers between the berings/frame and swing arm, and press fit bushings to put in the 13mm holes in the swing arm to fit the m10 bolt that holds it all together.


I also bougt a used fork, and new wheels with a qs 205 50H v3 4t motor. 19" front and 17" rear.


This is were I want your help :wink:

I don´t have all the bearings and parts for the steering. I have ordered some parts that i hope will be alright. But It will take about a month to get them.. However, it already seems like the shaft on the fork will be to short.


Maby I will have to lengthen it anyway, then I might as well put the stem for the handlebar on that.
But is there a stem that i can just bolt on? It looks like they have used something like that before. But on ebay I just found clamp on stuff.

I also need brakes. But it looks like that may be trouble.

What adapter do I need here?


The other ones I have seen has bolts from the side.

There also seem to be a space issue:


I guess it is possible to take some material from the hub to get the disk closer to the wheel, or are there disks that could fit?

A bit tight in the rear too:


That may not be a problem, and I can probably space out the wheel a little. It is very tight for the phase wires for the motor now anyway..

And what brakes should I buy? It is a jungle out there, and not much info of the difference..

I have been looking at shimano slx M7000, M315, diore M6000, M355, M8020 etc. Then there are a bunch of other brands..
It looks like that bike and fork should take a standard 1 1/8" threadless headset. They are very common. There's no reason it should take a month to get it. However, it also looks like the steerer tube on your used fork is too short, as you suspected. If you're really ambitious you might be able to press it out of the crown and press a longer one in, but more likely you just need to buy a different fork, and check the steerer tube length beforehand this time.

That fork is made for a direct mount stem. They are pretty common and you should have no trouble finding them on eBay or elsewhere.

That style of brake on the fork is called post mount. With some setups you won't need any adapter at all. If your setup does need an adapter, it should be available from the same manufacturer as the brake caliper.

Yes, disc rotor clearance is tight. They are less than 2mm thick.

If you have a local bike shop that stocks mountain bike parts, they will have all of this stuff in stock and be able to show you what you need. Buy from them instead of blindly on the internet and you'll get exactly what you need and help keep local businesses afloat!
Thanks for your reply, as you say it is a 1 1/8" headset. I have ordered a bunch of stuff of ebay, with slow shipping. That is why it will take a mounth. It will probly be possible to press the tube out, and aother one in. But I will probably just make an extention that fit in the tube and weld it in place. Then put in the lathe and make it smooth.

I want to use 203mm brake discs, I will take a look at rock shocks and see if there are any info there about brakes. I don´t know if there are any good bike shops here, to find info and parts. Most are just selling finished bikes.
If it's a steel steerer tube, the welded extension should work. I've done it a few times myself. Turn a tight fitting internal sleeve to bridge the connection between the old piece and the new piece. That will help keep it in alignment. Clamp it in V-blocks for welding if you have them. Even so, the welding will probably pull it out of alignment to some extent. After you weld it, you can spin it slowly in the lathe and check with a dial indicator. If it's out, you can get it to pull a little more in one direction by reheating the weld on that side.
Hi, I am building the same frame as you have but in black. There is quite a bit if info on here about these and there is a few builds going on at the moment. If you look at some of my other posts there's some guys on them building the same bike to so quite a bit of info there regarding the frame etc. Keep at it and keep posting,all the best. :bigthumb: :D
Thanks. I have looked around a bit, but not found very much details.
Anyway, I got my tires today and I am trying to decide what rear shock I will need:


This is with 200mm


And this is with 230mm.

I was thinking I shoud have 180-200mm, but now it seems more like I will need 220-240mm.
I think they have about 65mm travel, so I guess a 230mm will be about 200mm under load?

It will be lower in the front end too, so I think it will eaven out. At 200mm I will still have a little angle on the swing arm up to the frame, I think that will be good for grip on the tire. A little lifting effekt on the frame, and then putting more weight on the rear tire.

I have been looking at these shocks, vhat do you think?
Alright, some progress. It is a lot of waiting for parts, but some are showing up these days.


Rear sprocket, 16 tooth. I can´t have any smaller, I don´t think I will be able to pedal much on this bike..


I got these torque arms with the motor. Not very useful, rather weak and not a tight fit. And what is the big hole at the end of the slit for the shaft all about?



I made some changes to one of them to get some room for phase wires and a at least some support for the shaft.
(I just realized when I looked at the pictures now that made the cutout wrong for the phase wires :oops: )

I didn´t find any fenders i liked, maby I didn´t look hard enough :wink:
Anyway, if I find something it is hard to know how it will fit.


I decided to take some cheap mountainbike fenders and modify to make molds, so I can make my own fenders.



Something like that.


The front fender is starting to look like something, but the rear one is another story..
I have to change the shape rather much for it to fit the 17" wheel, and I havent been very successful so far.
Maby with a lot of filler, even more than on the front fender :wink:
It doesn´t really matter how. As long as it gets the right shape, and a somewhat enduring surface.

I got the seatpost recently, and the rear shock today (230mm).


Damn it is tall :shock:
I had to cut the seatpost a little, and mount the seat in the lowest position. Then it is almost to tall for me, and i am 190cm :wink:
A bit shorter shock would probably have been better, or a moto seat in the same hight as the frame.. Then I think the hight would be perfect 8)
But the plan was to try to make it look as much as possible as a bike :roll:
The fork steerer tube should stop about 4 or 5mm below the top of the plate if you're using direct mount stem... Not lower than the clamp bolt, but not flush with the top either.
Let there be light:


I got my handlebars and steam. I also bougt a hedlight and made some monts.
So much for not looking like a motorcykle :lol:


The front fender is ready for paint. I rather paint before i make the mold, it can get very hard to take them apart otherwise..
Or I could just use aluminiumtape to get a surfice, but with worse finish :?


I bought another rear fender, it is not the same profile though. But it seems to fit rather good. I think I will just try it like this and see how it looks.
Front fender ready for last sanding before paint:


Started on the other rear fender:


A monting bracket for both rear light and the mounting of the fender itself.




In the last picture I had to cut it up a bit again, stainless steel is a bit tricky when welding..



How I made the mounting brackets, it is 12mm hydraulic pipes that i press flat at the ends.
Then drill holes and grind them rounded.

I have now changed berings for the steering, and could see how long the tube should be.


I made the extention with 20mm to press down in the original tube.


I waited with cutting it to lenght so I could finish it in the lathe after welding.
Not the prettiest weld, I had to burn out some impurities.
Maby I did´nt clean enogh, the pipe was a bit rough on the inside :?


Finished, but not with the best finish though.
I had to use a longer tool in the lathe, with not the best cutting steel.
But it is strait, and the right size.

I then made a 10mm adapter/extention to get the upper bracket to clear the frame.



That way I get at least a little better steering angle.

I have also painted the front fender, ready to make a mold.


White is not the best color for it, because the gelcoat will be white.
(it will be difficult to see that there are good covering of gealcoat)
But I thougt I may want white for some parts for this build, so that was what I bought.

I have semimatt(?)(not flat, but not shiny) black, but I don´t think that will work for the mold.

I planned to use that on the fenders, but maby I should paint them white?
I think it actually looks rather good on the front fender :)
Brakes is finally coming togeter:



It was a bit of a struggle to get there, first I ordered a set from an ebay seller and got scammed.
They took some time before they shipped, but then everything seemed fine. Until it got delivered..
I got home, and did´nt find anything. Then I could see on the tracking that it was wrong postal code. I called the post office and asked about it, and they said it was the wrong mane and phone nr too..

I was able to get my money back from ebay, but I lost a month in shipping time etc. before I knew I was scammed.
I did´nt want to wait another mounth, so I ordered stuff that was closer to me (in eu, not china).

When I got everything, I realized the hose for the rear brake was to short. So I got a longer hose, brake fluid and bleed kit.
Well, now it is all there anyway, but a bit more expensive then I planned. Now the hose is a bit long, but I wanted to have some extra if I want taller handlebars later.


Front brake.


Rear brake and a thumb throttle with a switch to be used for variable regen.
I don´t have any switches on the brake handles, but I think it will be enogh to have it for the regen. I plan to use it for the most of the rear braking anyway.

Battery time:


I planned to build a battery from single cells, I tried to order 80 of them. But it did´nt work, and their costumer service was not able to tell me why. A few days later they were sold out, so maby they just didn´t have enogh.
Anyway, I did´nt want to wait. So I ordered packs instead.
A problem now is that I can´t test them, I ordered a charger a month ago, but it is still on backorder :? (icharger 4010 duo)

I am not sure how I should build the battery box, should I put pressure on the top and bottom of he packs?

I plan to series connect the packs in pair, so I get 10s1p. Then I will make the rest of the connections so I can disconnect them, so I can test every cell if there are any problems. Then connect them in pairs, so I get 10s3p. And the last connection for 20s3p I will have easy disconnectable, so I can charge like 2 10s packs.
Build coming along great.👍👍 will be good to see how you do your batteries? I'm doing the same build more or less...when I get time that is.🙂 enjoying this one. :bigthumb:
Okay, I will update a little. I have not got very much pictures, I did´nt bother to get pictures of details. It does´nt seem to be much interest anyway.

Painted fenders and parts:






I finally got my charger :)
I have been charging and discharging packs for 2 days or something. Here I am discharging in to some car batteries.
Why waste all the energy when you can use it again, right?
I think all the packs are good. I will look closer at the graphs later, to try to match them as good as possible to each other.

I also worked on the battery box. I planned to make it in fiberglass, strenghten with some divinycell(?)
I made some simple molds for the first 2 pices:


It is just some plasterboard monted on wood, and covered in aluminum tape.

But it did`nt work out as planned, fiberglass is hard to form over sharp edges. Maby it could have worked if I had made the side after the edge longer, so there would have been more to stick to.
I am talking about the small edges, some are marked with x in the picture.
The x acually mean that I don´t have to use that surface, but there are a bunch of others that I was going to use.

My failed attempts:



First I was using the woven fiberglass, then I thougt the normal chopped (or what it is called in english) would be easier.

Then I built it in aluminum instead :roll:



Maby I can get some better pictures of how it is constructed if there are any interest.
I am considering if I should drill holes for the cells to be able to vent to the sides, or if it is enough that it is opened upwards?
Some more pictures of the battery box:


It is mainly built of 2mm alu, with reinforcements on the pressure sides like this.
On the other side of the nanotech packs I used a 3mm plate instead, becase I did´nt want to use reinforcements when they face the other packs.

I also have some space under the box for wiring and space for screws and such.



Now I am trying to find out how I should fit these 2:

I haven't seen many other people put compression on LiPo packs like that. I've heard it improves cycle life and prevents puffing and increasing IR. It'd be great if you could post how the pack is doing in a year, my RC Car's Turnigy got slightly puffy after 6 months with no pressure on it.
There is one thing on the build that makes me cringe, and that is the routing of the rear power wire. A steel conduit welded to the frame and some sort of guard around the cable snake going to the motor would prevent the chance of nasty shorts. Everything else on your bike (especially the welds) look amazing. Keep up the good work.
Thanks for the replys. I have done some more work, but I have not had time to update yet.

About wiring, none is finished on the pictures.
I had just hanged the wiring for the motor there, to not have it dragging in the ground when moving the bike.
It is more finished now, and I have made some of the wiring for the batteries, charge connections and such things.
I drilled holes to the sides of the cells in the box, I hope it will help to release fumes if a cell vents.



It seems like I didn´t get any pictures of how it looks when it was finished, but I used this rubber carpet in the bottom:


I also used a special fabric tape on the edges to protect from wiring rubbing and damage the isolation.

I also built the packs in to 10s, and got rid of half of the xt 90 connectors.


It seems like I did´nt get any pictures of the finished packs, but I also shortened the wires a lot.

The beginning of the holder for the fuses:


Here it is finished, also with the holder for the charge connectors.
Also with a button for the pre charge resistor.

The side panel, not painted yet..


How it looks on the bike, without side panel:

I have built the electrical system too, the 12v converter:


I did´nt think about it when I bought it, but it has a common ground. I don´t like that, now it is a bigger risk to come in contact with high voltage, because the ground is the same in the 12v system :?
I am not running crazy voltages, so it is not that dangerous..

I didn´t find any relay for 84v, so I am using one for 48v with a resistor in series with the coil. It is for the converter, so I only have the load of the relay and the control for the controller on the ignition switch.


I have changed the rear shock too, 230mm was too long. Now I have 200mm, and I upgraded a little too.


I mounted a wattmeter too for now, so far I don´t have a controller with a display.


It was not intended for this bike, it is only for 100A. But it will do for now :wink:

I got some switches for the handlebars:


But I didn´t like them, far to bulky for this bike.
So I mounted some switches in the frame instead:

(The last picture in the previous post) The right switch is the 3 speed switch, the mittle one is lights off, parking light and for low or high beam. Depending on the left switch, which controls high/low beam. It also has the indicator light for high beam, I intend to use it just as an indicator if I decide to put another high/lo switch on the handlebars. A little problem though, I discovered that the indicator light was not for 12v :roll: I think I will be able to change it, if I can find the right lightbulb. It is really tiny..


Let there be light, this is just parking light.

I have also finally got my charger:


I also got a psu for it:



It was already modified for 48v output (about 48,5v) and connectors for the wires.
They seem a little weak for the claimed over 60A output though.

This was annoying, one of the (new) contact housings were glued together. So I could not take it apart to gain some space when soldering:


Finished the wiring for the charger:


Alright, another update. We are not really up to where I am in the build yet, but we are closing in :wink:

My plan is to use the nucular 24fet controller, but it is not finished yet.

So I got a cheap chinese controller to use in the meantime:



It is 18fet, should do 50A
I could not help myself from doing some changes to it before I eaven tried it..
I beefed up some traces and did a little shunt mod:


One of the shunts were mounted higher then the other two, I lowered that one and added a little solder.
I have xt150 on my (16mm2) battery leads. The leads for the controller looked a bit fynny in those:


I rode the bike a little, it was alright. But the controller only gave 55A, I was expecting more like 70A.

More shunt mod, and beefing up traces:


Some mosfets are fed from the upside of the bord, that trace is connected to the trace on the bottom. The bottom traces already had copper reinforcements, but nothing on the upper ones. On the first mod I added some solder, but now I wanted something beefier.



A lot beefier wires, and extra solder between wire and shunts. I didnt plan to solder the shunts that much..