• Warning!!

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    Be aware of your local country laws. Many laws prohibit use of modified EMTB's. It is your responsibility to check local laws. Ignoring it, has potential implications to trail access, and risk of prosecution in the event of an accident.

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MEGABOBRA: Bosch Smart System Derestriction for Rim Magnet - DIY Project with Support

pierrot364

New Member
Oct 25, 2023
1
1
France
Hi guys,
I just discovered this topic and I didn't read everything yet.
I'm french and I just bought a Canyon Strive: on. I had a Mondraker crafty upgraded with volspeed chip.
I would like to know if one of you have/can produce 1 additionnal chip to upgrade my Bosch engine with rim magnet ?
Thank you in advance for your answer and congrats for you engineering work !
Pierre
 

FINJP

New Member
Sep 30, 2023
4
1
Middle of Finland
239€ 🤪, material cost 30€ for end consumers, imagine if you can buy in bulk all components 😃

🤪🤪🤪
“ RimBoost pre-order at the special price of 239.00 euros. After the official release date, the RimBoost will cost 279.00 euro
Just sourcing the parts and around 60-80€ might be close cost for a one piece from Europe/Finland.
 

tatane

New Member
Jun 25, 2023
59
41
Southern France
Just sourcing the parts and around 60-80€ might be close cost for a one piece from Europe/Finland.
This is also just (part of, getting there later) the material part, it takes time to make them especially if you want to make them well and are not an electronics expert (which is the very reason why people are asking for some for sale/made by others who have the skills to make them to start with, since there's also that and the fact that smaller one tries to make that device, the harder it gets if not having the right skills and hardware, and yes we just got a new one to factor in with that since you definitely need to have at least some hardware to do the soldering there, maybe an oscilo to help with r&d etc ... )
Now, to @manu.w 's point, the one linked is coming out of an industrial process and there's a very low amount of r&d going on (they likely just did the same as the initial megabobra device does, and until proven otherwise I'd suspect they just copied the megabobra schematics and code from here to start with), meaning with the potential scale of sales they could get away with selling it way cheaper indeed, whereas I wouldn't be shocked at a hobbiyist or someone who created it/had to spend on extra hardware for both r&d and getting a build process that got us quality devices, asking for a bit more then "just the cost of parts" (mad respect to @megabobra for keeping it pretty close to the materials cost actually when he did a small batch, albeit I could understand that since he likely didn't make much out of something that took him a lot of time, this kind of comment may not encourage him - or anyone else really - in doing more 😅 )
 

E Bob

Well-known member
Feb 15, 2021
350
348
torfaen
This is also just (part of, getting there later) the material part, it takes time to make them especially if you want to make them well and are not an electronics expert (which is the very reason why people are asking for some for sale/made by others who have the skills to make them to start with, since there's also that and the fact that smaller one tries to make that device, the harder it gets if not having the right skills and hardware, and yes we just got a new one to factor in with that since you definitely need to have at least some hardware to do the soldering there, maybe an oscilo to help with r&d etc ... )
Now, to @manu.w 's point, the one linked is coming out of an industrial process and there's a very low amount of r&d going on (they likely just did the same as the initial megabobra device does, and until proven otherwise I'd suspect they just copied the megabobra schematics and code from here to start with), meaning with the potential scale of sales they could get away with selling it way cheaper indeed, whereas I wouldn't be shocked at a hobbiyist or someone who created it/had to spend on extra hardware for both r&d and getting a build process that got us quality devices, asking for a bit more then "just the cost of parts" (mad respect to @megabobra for keeping it pretty close to the materials cost actually when he did a small batch, albeit I could understand that since he likely didn't make much out of something that took him a lot of time, this kind of comment may not encourage him - or anyone else really - in doing more 😅 )
This is also just (part of, getting there later) the material part, it takes time to make them especially if you want to make them well and are not an electronics expert (which is the very reason why people are asking for some for sale/made by others who have the skills to make them to start with, since there's also that and the fact that smaller one tries to make that device, the harder it gets if not having the right skills and hardware, and yes we just got a new one to factor in with that since you definitely need to have at least some hardware to do the soldering there, maybe an oscilo to help with r&d etc ... )
Now, to @manu.w 's point, the one linked is coming out of an industrial process and there's a very low amount of r&d going on (they likely just did the same as the initial megabobra device does, and until proven otherwise I'd suspect they just copied the megabobra schematics and code from here to start with), meaning with the potential scale of sales they could get away with selling it way cheaper indeed, whereas I wouldn't be shocked at a hobbiyist or someone who created it/had to spend on extra hardware for both r&d and getting a build process that got us quality devices, asking for a bit more then "just the cost of parts" (mad respect to @megabobra for keeping it pretty close to the materials cost actually when he did a small batch, albeit I could understand that since he likely didn't make much out of something that took him a lot of time, this kind of comment may not encourage him - or anyone else really - in doing more 😅 )
I’d happily pay him full amount for a plug n play unit, As you say wouldn’t be at all surprised if those guys copied his electrickery….
 

megabobra

Active member
Jul 24, 2022
220
237
Australia
This is also just (part of, getting there later) the material part, it takes time to make them especially if you want to make them well and are not an electronics expert (which is the very reason why people are asking for some for sale/made by others who have the skills to make them to start with, since there's also that and the fact that smaller one tries to make that device, the harder it gets if not having the right skills and hardware, and yes we just got a new one to factor in with that since you definitely need to have at least some hardware to do the soldering there, maybe an oscilo to help with r&d etc ... )
Now, to @manu.w 's point, the one linked is coming out of an industrial process and there's a very low amount of r&d going on (they likely just did the same as the initial megabobra device does, and until proven otherwise I'd suspect they just copied the megabobra schematics and code from here to start with), meaning with the potential scale of sales they could get away with selling it way cheaper indeed, whereas I wouldn't be shocked at a hobbiyist or someone who created it/had to spend on extra hardware for both r&d and getting a build process that got us quality devices, asking for a bit more then "just the cost of parts" (mad respect to @megabobra for keeping it pretty close to the materials cost actually when he did a small batch, albeit I could understand that since he likely didn't make much out of something that took him a lot of time, this kind of comment may not encourage him - or anyone else really - in doing more 😅 )


Thanks Tatane.

Frankly the main reason I'm reluctant to accept payment for any further devices is two-fold. Firstly, the initial batch revealed compatibility challenges with different motor variants (CX vs non-CX). I ended up issuing a couple of refunds for this reason to buyers who could not get their devices to work in their motors.

The second reason is lack of feedback from the other buyers, so I'm unsure if they're working successfully. I'm guessing no news is good news, but I'm also conscious that these may simply have not yet been installed yet.

I have no interest in offering a device that buyers perceive to be unreliable, incompatible or of low-quality, or simply anything less than their expectations when handing over their own money. Similarly, this project is not intended to be a cash-grab like some of the commercial copies that have been linked above (279Euro??).

Your own experience with the reversing polarity is a great step forward, well done.

I've been working on a few things on my own device that I'd incorporate in a V2 of the megabobra, aimed at addressing some of the challenges V1 showed:
  • Removing the reliance on the low power port (LPP) - many members here have noted the trouble they've had with their local bike store being unwilling or unable to activate their LPP, or charge a fortune for it!
  • Removking the reed sensor at the rear wheel - some members had a hard time running the cables to the wheel as their frame didn't easily accomodate it. Instead, V2 would retain the original Bosch rim magnet, removing this need for cabling altogether.
  • Reducing the size of the electromagnet coil to assist with placement - I've learned I'm a bit spoiled for space in my Voima where other members have had to drop their motors out of the frame to get access for placing the coil.
  • Incorporating the same remote troubleshooting LEDs I have on my own unit - These show reed sensor pickup and electromagnet firing. Assists mostly with install so they'd be mounted direct to the device, but I like to keep an eye on my own regularly, where I have the LEDs mounted externally so I can monitor them while riding.
I expect these features would make the devices significantly more user friendly without increasing the cost to build them. Nothing's in concrete yet, but it's good to keep this project alive.
 

aegidius

New Member
Sep 30, 2023
39
25
brisbane
Removing the reliance on the low power port (LPP) - many members here have noted the trouble they've had with their local bike store being unwilling or unable to activate their LPP, or charge a fortune for it!
That's a real surprise to me. I have a friend who was told that plugging into the LPP would void his warranty (he wanted to put a USB charger on it for the phone). Different LBS's have different stories, but if I was questioned on it, I would gently remind them that (a) the LPP is documented, and (b) the cable for it is made by Bosch and is freely available. I bought one through the LBS I bought the bike from, and they did not worry about it at all. Also, the bike came with the LPP activated, I did not have to ask them to activate it.

If you get any crap about the LPP then just splice into one of the light cables (the light ports have more current capacity anyway). The advantage of the LPP is that it stays on when the lights are turned off.

Great to see development continue on this, too. I've been working on a similar thing, but more emphasis on the algorithms used rather than getting it manufacturable, and for the spoke magnet motors. Mine is running on an Arduino that sits up in the battery compartment.
 

manu.w

New Member
Aug 5, 2023
80
35
belgium
Hello,
Nice these enthusiastic talks.
@tatane , what version of the motor system software are you testing on?

Actually, this is my biggest concern. I am on 4.21.0.
As said, I am successfully ran for hundreds of km with the logic I mentioned above (loop code logic).
If you have the latest motor software, could you test this simple logic (so without the polarity reversion, just the “positive” pulse length)
Thanks
 

aegidius

New Member
Sep 30, 2023
39
25
brisbane
Mine is running on an Arduino that sits up in the battery compartment.
Forgot to attach the github link. This SW is doing the job of a speed/cadence and opposing-force power meter at present. It communicates with standard cycling apps (like SuperCycle) via BLE. I'll look into RemoteXY with interest for controlling stuff that the cycling apps can't do (I have a love-hate relationship with Androd Studio, it's actually more hate-hate atm, so good to get away from that)
 

AlumiPro

New Member
May 1, 2023
130
64
California
Well I was finally able to go on a 23mile ride with the Megabobra installed.
First few miles I got no error codes. Then I took a down hill line with jumps, in RACE mode(getting more air time than I’ve ever gotten before on these jumps, due to me being able to push past the previous 20mph limit)😁 Unfortunately half way down this run error 523003 came up while also removing assisted power, forcing me to stop and restart the system. I went a bit farther in RACE mode and got the code again within 1min, also hitting a good jump in that 1min. At this point I left it in EMTB mode and rode another approx 15miles (natural single track rocky tech up and down hill) with no error codes or problems, at times surpassing the previous 20mph limit. Then I got a 523001 error code, forcing me to once again stop and restart the system to continue.
By the end of my 23mile ride I received three 523003 error codes and two 523001 error codes. Luckily these error codes reset with powering off/on, returning full assisted power.
My Megabobra is multiplying by 1.6(32mph new limit) on this ride my average speed was 10.2mph and my max speed was 28.3mph.
I would be ok with reducing the Megabobra speed limit to 28mph if I new it would solve this problem and not create error codes, but I’m guessing it won’t?
I’m also guessing my reed sensor positioning or the spoke magnet I chose to use(not using the one Megabobra provided) would produce these error codes?
Keep in mind my Bosch Software is up to date with version 8.16.0

IMG_6801.jpeg IMG_6802.jpeg
 
Last edited:

aegidius

New Member
Sep 30, 2023
39
25
brisbane
Is it possible that the motor is confused by picking up the original magnet as well as the Megabobra coil? Just a wild guess.
 

AlumiPro

New Member
May 1, 2023
130
64
California
Is it possible that the motor is confused by picking up the original magnet as well as the Megabobra coil? Just a wild guess.
The original Bosch rim magnet is removed. I keep it in my riding pack just in case I’m forced to abandon the Megabobra and reinstall the rim magnet on the trail…..I would also remove the spoke magnet to deactivate the Megabobra pulse.
 

megabobra

Active member
Jul 24, 2022
220
237
Australia
The original Bosch rim magnet is removed. I keep it in my riding pack just in case I’m forced to abandon the Megabobra and reinstall the rim magnet on the trail…..I would also remove the spoke magnet to deactivate the Megabobra pulse.

Thanks for the info Alumi.
Intermittent events like this suggest to me that it's magnet/reed sensor related, causing the electromagnet to fire twice in quick succession, resulting in spuratic speed readings and the error above.

A couple of things to try:
  • With the rear wheel off the ground, try rotating the wheel's magnet back slowly past the reed switch by hand - ie don't use the pedals, just turn using the wheel. Give it a few rotations, even moving it back and forth past the switch. Watch the speed displayed on the kiox. You're looking for any sudden surges in speed
    • Ideally, you would your phone to monitor the magnetic field coming from the electromagnet to be know when it's firing (in case the Bosch app/kiox doesn't display the invalid speed readings, instead just triggering the error)
  • You mentioned you're using a different magnet at the wheel. You want a magnet of the least strength possible which will still trigger the reed switch, as this will help to minimise the chance of a double read.
    • Maybe try adding some more distance between your magnet and the reed sensor
  • Finally, try moving the reed sensor slightly. The magnet should pass down the middle (along its length) of the reed sensor. Also try spinning the reed sensor ~90deg along its axis so that a different face points towards the passing magnet.
The megabobra code does feature a line to try to ignore these double reads, ignoring any readings that have occured within 100ms of the last. However I think this could do with an improvement to alter this 100ms dynamically based on the speed you're presently travelling. For example, at one relovution per 100ms the bike would be travelling ~80kph (29" wheel). Importantly the double read can happen at any speed. If the motor's seeing a speed of 10kph, I don't think it matters if it then suddenly sees a reading of 30kph or a sudden reading of 60kph - both are unaccounted for without pedalling or time to accrue speed when rolling down a hill.
Using a dynamic time to debounce the sensor might mean when travelling at 10kph, ignore readings within 600ms, when travelling at 30kph, ignore readings within 250ms etc. This will offer tigher control of these double readings.

Anyway, try the physical tests above. If there's no improvement, let's try a code change.

Let me know how you go.
 

AlumiPro

New Member
May 1, 2023
130
64
California
Thanks for the info Alumi.
Intermittent events like this suggest to me that it's magnet/reed sensor related, causing the electromagnet to fire twice in quick succession, resulting in spuratic speed readings and the error above.

A couple of things to try:
  • With the rear wheel off the ground, try rotating the wheel's magnet back slowly past the reed switch by hand - ie don't use the pedals, just turn using the wheel. Give it a few rotations, even moving it back and forth past the switch. Watch the speed displayed on the kiox. You're looking for any sudden surges in speed
    • Ideally, you would your phone to monitor the magnetic field coming from the electromagnet to be know when it's firing (in case the Bosch app/kiox doesn't display the invalid speed readings, instead just triggering the error)
  • You mentioned you're using a different magnet at the wheel. You want a magnet of the least strength possible which will still trigger the reed switch, as this will help to minimise the chance of a double read.
    • Maybe try adding some more distance between your magnet and the reed sensor
  • Finally, try moving the reed sensor slightly. The magnet should pass down the middle (along its length) of the reed sensor. Also try spinning the reed sensor ~90deg along its axis so that a different face points towards the passing magnet.
The megabobra code does feature a line to try to ignore these double reads, ignoring any readings that have occured within 100ms of the last. However I think this could do with an improvement to alter this 100ms dynamically based on the speed you're presently travelling. For example, at one relovution per 100ms the bike would be travelling ~80kph (29" wheel). Importantly the double read can happen at any speed. If the motor's seeing a speed of 10kph, I don't think it matters if it then suddenly sees a reading of 30kph or a sudden reading of 60kph - both are unaccounted for without pedalling or time to accrue speed when rolling down a hill.
Using a dynamic time to debounce the sensor might mean when travelling at 10kph, ignore readings within 600ms, when travelling at 30kph, ignore readings within 250ms etc. This will offer tigher control of these double readings.

Anyway, try the physical tests above. If there's no improvement, let's try a code change.

Let me know how you go.
Well shoot!….I figured the stronger the magnet the better, and as close to the reed as possible! I ordered three different spoke magnets just to have options. The one I chose is a cylinder type and honestly I think it is the weakest one I ordered because it’s incased in plastic. Maybe the cylinder shape sometimes triggers double pulse!?
I ran the reed wire/sensor along the bottom of the rear brake line through the swing arm and used a long piece of electrical shrink tubing to secure it to the brake line and disguise it! I’m really happy with how hidden it is being shrink tubed tight to the bottom of the brake line. My next ride I will take all three types of spoke magnets to try out, they are very easy to swap out on the trail.
The red oval outline in my pictures indicate the reed, while the yellow oval outline indicate the spoke magnet.

IMG_6814.jpeg IMG_6816.png IMG_6815.png IMG_6811.jpeg IMG_6809.jpeg IMG_6812.jpeg IMG_6807.jpeg IMG_6810.jpeg IMG_6813.jpeg
 

megabobra

Active member
Jul 24, 2022
220
237
Australia
Ahhh ha. Further to Manu's thoughts earlier in this thread, I wonder if your issue might be with the magnet (and its orientation) you have mounted. While the alignment is spot on, the as the magnet passes the reed sensor it will first show one pole, say positive, and then as it continues past the negative pole will show to the sensor. It could be that the reed sensor sees both poles with a gap in between leading to a double read.

The smaller cylindrical magnet you posted won't have this issue.

With the current on you have installed, you could try changing the orientation so that it's pointing directly at the sensor. So I guess you would have it parallel to the rear axle - does that make sense? This would ensure only one magnet pole is ever passing the sensor. Not sure how you'd keep fixed there though.....
 

AlumiPro

New Member
May 1, 2023
130
64
California
Ahhh ha. Further to Manu's thoughts earlier in this thread, I wonder if your issue might be with the magnet (and its orientation) you have mounted. While the alignment is spot on, the as the magnet passes the reed sensor it will first show one pole, say positive, and then as it continues past the negative pole will show to the sensor. It could be that the reed sensor sees both poles with a gap in between leading to a double read.

The smaller cylindrical magnet you posted won't have this issue.

With the current on you have installed, you could try changing the orientation so that it's pointing directly at the sensor. So I guess you would have it parallel to the rear axle - does that make sense? This would ensure only one magnet pole is ever passing the sensor. Not sure how you'd keep fixed there though.....
I’ll try the other two styles of spoke magnets I have.
As always thanks for the help
 

manu.w

New Member
Aug 5, 2023
80
35
belgium

Keep in mind my Bosch Software is up to date with version 8.16.0

If you could be sure that your reedswitch is ok, this means that upgrading the software of the Bosch system works with the simple “square pulse”😃?…
Let us know your findings
Thanks for sharing
 

tatane

New Member
Jun 25, 2023
59
41
Southern France
AFAIK square pulse would "work" with any version, at least for the first 1000km ... what we don't know (and won't until someone does that much with it on latest firmware) is if all the stuff from the patent would be implemented, and what version they would implement which of those "features".
Since big chunks of that patent hint at "comparing the magnetic pulse with a stored sample" as well as "monitoring the deviation of the magnetic field sensor signals separately according to the spatial directions possibly using different thresholds" , this hints that they can actually compare any point of the shape of the pulse to a stored reference one, which is unlikely to be a square pulse 😅
While this may (or may not) work forever on older firmwares, it may also (or may not) be used in more recent ones, but we can't really know that, hence my "better safe then sorry" approach there in trying to be as true to the original signal as possible ;)
 

tatane

New Member
Jun 25, 2023
59
41
Southern France
So we could use a hall sensor instead of a reedswitch and mimic that signal, is this what you do?
Not yet, but guess it could indeed be a good addition, altho we'd still may not be getting the exact same pulse from our spoke magnet there ...
@megabobra did pique my interest with his idea of actually keeping the rim magnet and using that, this way with a hall sensor we could actually truly replicate the pulse (applying it our multi to modulate its lengh vs speed), but curious how you'd get that without the rim magnet disturbing the whole system ? (if the engine can still sense it then we get double pulses, and it's a pretty strong magnet, to the point that I'm wondering if some of the issues I've (and some others semms to) been having in my first tests of the device were due to actually still having the magnet in my backpack and it potentially disturbing the whole system with its strong magnetic field
 

manu.w

New Member
Aug 5, 2023
80
35
belgium
Not yet, but guess it could indeed be a good addition, altho we'd still may not be getting the exact same pulse from our spoke magnet there ...
@megabobra did pique my interest with his idea of actually keeping the rim magnet and using that, this way with a hall sensor we could actually truly replicate the pulse (applying it our multi to modulate its lengh vs speed), but curious how you'd get that without the rim magnet disturbing the whole system ?….
Putting it on the front wheel🤔😉
 

tatane

New Member
Jun 25, 2023
59
41
Southern France
Putting it on the front wheel🤔😉
can't imagine running wires from the front wheel to the engine there ... that would take a lot of work and wiring to get it through the internal routing in the downtube back to the device, how would that be more practical then having a reed switch ? 😅

EDIT : actually could have two device with BLE comms between both of them, but that means having one battery operated (can be done but adds quite a chunky piece attached on the front wheel, and makes the whole thing more complex/prone to issues)
 

AlumiPro

New Member
May 1, 2023
130
64
California
Just to clarify; when I talk about my spoke magnet I’m talking about the new aftermarket magnet I added to my spoke to pass by the Megabobra reed switch.
The Bosch system magnet is called a RIM magnet(secured to the valve stem)
 
Last edited:

E Bob

Well-known member
Feb 15, 2021
350
348
torfaen
I Dont know if im being helpfull or not but.. Someone just started a post re galfer shark brake rotors, Which have a cut out to take a magnet.
 

AlumiPro

New Member
May 1, 2023
130
64
California
Here’s something to think about that I haven’t discussed on this thread.
The first 50miles I put on my Bosch CX Race motor I had Hustle magnetic pedals installed(magnet to my riding shoes, instead of clips). I also had no Megabobra installed. The first 50 miles I rode(two different rides) I didn’t get a single error code BUT because the pedals have such a strong magnetic force and they pass close to the back of the motor, they were causing the speed to fluctuate all over the place due to the Bosch system sensing the pedals magnets passing by. Doing hill climbs the motor would occasionally stop assisted power (dangerous on tech climbs) because it’s seeing speeds over the 20mph limiter, due to the pedals rotating at a faster speed than the rim magnet. At this point my speed spiked showing 27mph for a split second, when I was actually doing 4mph! The motor assistance re-engaged power after the split second 27mph spike had dropped drastically below 20mph, allowing me to continue climbing. This all happened with NO error codes.
I then went on my 3rd ride with no Bosch rim magnet at all. The pedals magnets were the only things passing close to the Bosch sensor which was showing a very fluctuating speed, but I was able to ride. Approx a mile or two into my ride the motor assistance shut off with an error code on the screen. I had to power off/on and put the Bosch rim magnet back on, to complete my ride. The rest of my 20mile ride using the magnetic pedals along with the Bosch rim magnet I had no error codes, BUT the speed was fluctuating and spiking all over the place due to the pedal magnets!
I share this because it blows my mind that I was NOT getting any error codes with the magnetic pedals fluctuating/spiking the speed sensor. Yet now with us trying to derestrict the system, we think the system is so sensitive and smart to any changes it can’t make sense of! This is very odd to me. The only other thing I can add to this is that the first 70miles I put on my bike with the magnetic pedals, the firmware was not updated yet…..not sure what firmware stage it was at.
After those three rides at 70miles total, I removed the magnet pedals and am now running clips again….which I like better.
 

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