Cromotor + MethTek Monster 24FET + 20S lipo build

During my holiday, I have been thinking about designing my own frame (asking someone to TIGweld it). In order to direct my inspirations and ambitions, I went through the pics and vids thread, and created a compilation of nice bikes here on ES. It was only after I created it, that it occured to me that others may like the picture as well.

The new bike will replace the current bike as high speed commuter. Current criteria:
  • built for >40mph / 65kmh. This is about the highest speed I would dare with a bike. I feel most comfortable at speeds around 30mph / 55kmh.
  • full suspension
  • as stealthy as possible: aka should look like a normal DH/XC MTB
  • able to carry 1.5kwh to 2kwh of lipo
  • able to easily swap lipos for 20S
  • able to easily swap controllers
  • able to easily charge with either lipos on the bike (at home) or with the lipos taken out (office)
  • large swingarm with adjustable dropout width & depth, to easily accept my cromotor and other hubmotors
  • longer wheelbase. Thinking about 130cm.
  • 3mm alu plates for all parts, possibly thicker if needed.

Build will take the whole winter reaching into the summer. I have a working bike, so there is no urgency.... which is good.

This is NOT meant as a contest or comparison or what. It is just what it is, a picture with nice bikes, so that I can copy the best parts of each for my own illusional frame.


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Just paid methy's invoice for the superduper controller. The wait has started again........

... will post my experiences of course!
I changed tires. My rear Schwalbe Marathon Plus slicks were toast after around 500km. There are yellow patches of kevlar shining through (pic to follow). I replaced both front and rear with a Schwalbe Marathon Plus MTB. Removing the rear wheel from the frame was a piece of cake. Getting it back in took about 10 minutes, but only with the help of my father-in-law. I may build some tool to assist me with this :idea:


Anyway, I also cleaned up a lot of wires. I also made a mistake somewhere, so my lights are off, which is not good in the current wheather. At least the motor is running fine. I changed the current limits in the Lyen 18FET controller to 100A/220A battery/phase current, and the bike is very snappy. Topspeed is still around 70kmh at 84V, and when accelerating (drawing 80A) voltage sags to 77V. Obviously, when doing that too often, range diminishes rapidly. I try to stay below 30Wh/km (48wh/mile), but it is just way too much fun....

Methods gave the controller to the mailman before the weekend. It's probably sitting in the airplane right now. :p
Alan B said:
Thanks for including my bike in your collection. Some excellent bikes there.

The stability of a longer frame dual suspension setup with mounting and covers for batteries/etc is really nice. About the only thing I've missed on my Greyborg Warp is a good cargo rack.

Thanks for following my ramblings here...
small update: when driving home through town, I was caught speeding by an automatic camera. I was keeping up with traffic, with the car in front of me doing 58kmh, and me as well. Max speed in town in 50kmh, so the camera flashed and I am sure I am in full frontal in the picture.

Now, I am also sure that there is no way the cops can find out from the picture where I live and send me a ticket. However, I do regret that they have a picture of me in the first place. Oh, and current Swiss Regulations state that ebikes are motorized bikes. Speed limits are valid for all motorized traffic. Including pedelecs and other ebikes. Regardless whether there is a tacho onboard....

Ah well, when Methy's controller comes in, it will only get worse... :twisted:
Mailman came...

Sorry for the bad pictures. More to follow.




dbaker said:
Alan, what is the wheelbase of your Borg? 8)

I just made a quick measurement,wheelbase is about 52 inches unladen. Judging by my car bike rack it is pretty much identical to the bikeE, and about as long as the rack can go. At 5kw it has no tendency to get air under the front wheel though the front suspension is definitely unloading, and if a pedal hits pavement in a turn it doesn't cause much of a disturbance at all. It rides very calm and stable. With the small 17" moped rims and tires there is not a lot of pedal clearance so I have to watch pedaling through turns. I have had many pedal strikes with no problems, I suspect the suspension takes it and the wheels remain in full contact so there is no handling issue.
I guess there is no way for them to prove it was U going 58km per hour, if there was a car beside you?, unless they take two pics? :mrgreen: I just fitted a cromotor, WOW! Now i know what you guys are talking about!!!
Alan B said:
I just made a quick measurement,wheelbase is about 52 inches unladen.

that would be around 130cm. My conversion resulted n 125cm wheelbase, unloaded, but with batteries.
hydro-one said:
I guess there is no way for them to prove it was U going 58km per hour, if there was a car beside you?, unless they take two pics? :mrgreen: I just fitted a cromotor, WOW! Now i know what you guys are talking about!!!

Well, they DID make two pictures, cause I saw two flashes. First the car in front of me, then me.... :cry:

Good that you have the cromotor. Next step will be venting the thing, because with Methods' Monster 24FET, the cromotor will be beaten...








Text to the photos will follow. For the time being, the last two photos show my own dabbling, having used red high temp silicon to fixate a green thermistor onto the body of a FET.
I thought high temp silicone was rather insulating.. Is this an acceptable thermal path? or it the sensor flat and flush against the fet with thermal paste, then covered with silicone? I used aartic ceramique thermal epoxy but if this is a widely available cheap alternative, I see no reason getting the arctic
Hi Hillzofvalp,

Yes, the high temp silicon is hopefully very insulating, both from electrical and heating perspective. Yes, the sensor is flat and flush against the FET, but without thermal paste. I but covered the sensor and 3 fets with the solicone, so that the sensor is very well fixated. I also used double layers of heatshrink around the feet of the sensor and its wires..

Yes, thermal paste would have been ideal. Then again, I think there is only a slight delay in temp increase between FET and sensor, with the sensor so close to the FET. I really should back off in case the sensor is anywhere near 140oC, because according to the datasheet the rdson has more than doubled at that temp.
Long time without too much action. Rain and hectic work.

Need to think now about a good way to compare the new MethTek Monster with the Lyen 18FET. I know it is not a fair comparison, but I would like to standardize as much as possible anyway. Having a CAv2 with current throttle connected via the DP cuts off anything above 99A. Therefore, I am back to a voltage throttle connected directly to the controller. Brr, very sensitive....

Furthermore, my front fork is leaking oil. I am trying to service it myself, using the enduro manuals. I am very impressed with the amount of information on suspension forks can be found here. Heavily recommended!
Front suspension fork - Enduro seals
OK, I am very happy with how this turned out. My REBA was leaking, and I turned to an old Fox F100 that was also leaking. I had ordered the 32 mm Enduro Seals for Fox, and was eager to learn to service my forks myself, and change the seals / wipers to the Enduros while at it. My other Fox had undergone a service for CHF 200 !!!, and all they did was replace the seals and replace the oil.

Having never disassembled a front fork before, I read and re-read the very good Enduro manuals, especially those for the Fox F100 and 36 TALAS. As mentioned in my previous post, heavily recommended read for anybody using front suspension! I also did a search for Enduro seals on Google, and ran into this MTBR thread, which describes some nice user experiences combined with some very good expert answers from Chris2fur, who is the man behind the Enduro seals. During the weekend I faithfully followed the steps described in the manual, and I really got to know the insides of my fork. I replaced the seals / wipers with the Enduros, and replaced the oil with Rockshock 2.5WT suspension oil (bike handler did not have any other brand available). The wipers are really tightfitting. The fork is very smooth, but obviously needs a bit more dialling in from me. This morning I drove to work and it is one very smooth ride. The Fox is also much more stable than the REBA. Very happy with it.

Full grip throttle
As mentioned before, I switched to a voltage throttle connected directly to the controller, bypassing the CA. Now, I will discuss the reasons for that in the next paragraph, but I just wanted to state something about this full grip (motor-cycle like) thing. I had a half grip throttle in use for over a year now, and I have gotten very used to the fact that I can hold on tightly to the steering bar ends with both hands, without influencing the throttle. With the full grip throttle, I can not do that anymore. This is where I have found that with a 30kg 5kW bike going 35mph / 55kmh, I really appreciate gripping the steering bar with both hands. With the full grip throttle, I ended up fearing for each bump and going much more slowly than otherwise, because every bump would slightly change the right hand position, and with it the throttle. I will go back to half grip as soon as I get home.

Direct voltage throttle
As mentioned before, I switched to a voltage throttle connected directly to the controller, bypassing the CA, the main reason being that my CAv2 is maxed out at 99A and 99kmh. Now the speed is not a problem, I feel most comfortable at 50-55kmh, and it is nice to be able to go 70-75kmh if needed. However, with my mountains, and with the MethTek Monster in house, the 99A is a bit too restrictive. I also have the CAv3beta, but it is only since Rev19 that I have enough confidence to start giving it control to my throttle. Anyway, I bypassed the CA, and connecte the throttle to the controller directly. Big mistake!

Methods kindly provided me with a (full grip) throttle that has some arbitrary scale (1-9) on the grip and a big green ebrake button. As expected, there was no reaction from the controller for the first 25% rotation of the throttle. Under noload conditions, the next 50% increased speed from 0 to 75kmh (1.5A - 2.5A), and then the last 25% from 75kmh to 95kmh (2.5A - 3.5A). This was as expected. However, I was absolutely not prepared for the real life implications, after being used to the nice and civil curren throttle via the CA. For me, having to turn the throttle for 25%, and then an almost instant 30A burst to get the motor running from 0 to 10kmh is crazy. For every traffic light, I was bracing myself while turning the throttle for what seemed an endless time, and only then very very slowly move the throttle in order not to be thrown off.

Mind you, this is with the Lyen 18FET still in place. I cannot even fathom what the results would be with the MethTek Monster. Therefore, I will need to go back to the current throttle via the CA. I will probably need to rely on the CAv3 to get past the 99A limit. But I have come to rely on my current throttle for safe driving. This is really a compliment to Justin and his team, who built the CA in the first place!

Weird brake down
So, I arrived at my work not too happy. At about 2/3rd of my route, I heard a weird "crack", and then my motor stopped working and when pushed it demonstrated this typical dragging behaviour that makes you fear for your FETs. Upon closer inspection, the disc brake was hanging loose, 5 out of 6 screws that fixate it to the cromotor had dissappeared, and one of the legs of the brake caliper (Elixer 7) had broken. I put the bike at the side of the road, secured it with a strong chainlock, and walked for 60minutes to my working place. I will pick it up tonight with the car.

So, my theory of what happened; the disc brake was secured to the cromotor using a 2.5mm spacer to increase disk caliper clearance from Grin. The bolts (with locktite) were therefore only partially inserted in the holes in the cromotor, and must have come loose since I last put them there. Then the disc came loose, and the rotation of the loose disc broke the disc caliper's foot, at the same time increasing the load to the motor tremendously. The last thing probably burned some FETs.

I will be able to better diagnose when I get home. Sure can try the sensorless Lyen controller and then I have a good justification to put on the MethTek Monster :twisted:
Update - Controller
Yesterday evening, after I got home, I took the car and picked up my bike. I removed the broken brake caliper, fixated the disc to the hub with the appropriate bolts and a bit more blue locktite, connected the Lyen 18FET controller and opened the throttle. It works. So no damage to halls / FETs. Right? Well, I have decided to put the MethTek Monster to work anyway. So, I am in the process of elongating the hall and phase wires, change a lot of connectors, put the CA back inline with a current throttle, and then see how far we can go.... I estimate my bike is now out of order for at least another day.

In the meantime, my wife kindly agreed to let me use the car to drive to work. I took my youngest (3y/o) to kindergarten, and then left for work. Driving around a small kid in the pooring rain, a car does have it's advantages.... :|
Hmm. Not really a happy day. I may have blown the MethTek Monster due to a failing hall. I tested different hall-phase combos with the MethTek Monster, and suddenly there was this explosion-sound inside, a nice spark outside, and the telling smell of burned circuits/caps. Only after the magic smoke appeared in the MethTek Monster did I use my Lyen tester. And behold, one of the hall sensors is dead.

But I am afraid the MethTek Monster is dead as well.... :( :( :(
OK, I have a functional bike again.

Old setup: half grip current throttle, CAv2, Lyen 18FET, 20S lipo. Hall wires replaced. 5hours work to diagnose, replace, and assemble again.

Sorry, but I probably blew the MethTek Monster. No time now to diagnose and/or try to repair.

At this moment work is priority one. Still working late tonight. Bike is commuter first.
Stuttering motor
When pulling up from standstill, pulling >20 amps gives my bike the stutters. No, it's not another mechanical failure. Turned out I had increased IntAGain in the CA too much (300). I set it back to 100 and the stuttering has almost disappeared.

CA settings
So, with a current throttle in place (see page 19 of teh CA manual) in a high power setup (100A limit on the controller, CA limited to 80A again), the CA manual specifically states on page 13 that "For more powerful systems (...), it is necessary to tone down the appropriate feedback gains in the advanced setup menu". On page 16, IntAGain "determines how rapidly the over-ride output will ramp down". Too low will result in considerable overshooting, while too large will cause the controller to oscillate. Obviously, when riding my bike, I don't care too much about the overshooting, and could go even lower for better performance. And the "stuttering" that I experienced, was really some sort of "oscillating".

All of this and more can be had in the CAv3. But I have not had the time to install it in such a way that it is reliable enough for a commuter.
Brake rotors are sharp. Goes through phase wires like through butter.

Dented hall wires. Completely replaced.

Photos of the blown MethTek Monster to follow....
I love following your thread here and love the look of your bike.

Been waiting for an update on the methek monster.. really sorry to hear that sounded strange that the controller
could have failed based on what happened.. hopefully it works out somehow.

At least your up and riding.
It's all about the looks....