DIY Mechanical Dongle

Gringo

Esteemed Pedelecer
Jun 18, 2013
991
543
Northampton
I’ve had this idea bouncing around for quite a while, if I turn my speed sensor magnet slower than the wheel and I get the ratio correct (large pulley dia = small pulley dia + 61%) I can set the display to show kph,the bike will think it’s doing kph and keep the assist going up to 25kph but I’ll actually be doing 25mph :cool: so is afternoon I had a little play.
First up I turned two pulleys, one that fits behind the brake disc and a larger one to mount on a modified plastic torch bracket on the frame. I fitted a magnet to the larger pulley and it now passes the repositioned sensor at a slower rate than the wheel.
I’ve only had time to ride up and down my street but the plan seams to work (checked against another Speedo fitted to the front wheel)
0FDC872F-5D9B-4C5E-8383-D1E4D87C164D.jpeg5EEFB6B4-8EAD-4C4B-AAA0-28DC59B86464.jpeg63502134-285E-4016-9698-F9179D7D5FFC.jpeg37D37819-16D5-4187-A987-F93013B73416.jpeg
 

ebiker99

Pedelecer
Feb 17, 2019
137
44
Interesting idea, doesn't the wheel behind the brake disc make the whole hub assembly quite a bit wider though? How does it still fit in the frame?
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
991
543
Northampton
doesn't the wheel behind the brake disc make the whole hub assembly quite a bit wider though?
The pulley fits over the body of the disc carrier/hub not between the two so there’s no change in width ;)
 
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Woosh

Trade Member
May 19, 2012
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utterly brilliant!
have you made an STL file for it?
yours is an elegant solution, quicker to fit and a lot cheaper than buying one of those electronic dongles.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
1,517
280
Basildon
Cannot you just remove the magnet?
The one on the wheel of my TONARO fell off yonks ago.
Bosch is too clever for that. There software doesn't allow to run without a speed pulse, neither will it allow to run with the speed pulse in proportion to the motor speed.
 

Woosh

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May 19, 2012
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Bosch is too clever for that. There software doesn't allow to run without a speed pulse, neither will it allow to run with the speed pulse in proportion to the motor speed.
not just Bosch. A lot of controllers cut out after a little while if the speed reading is zero.
 

ebiker99

Pedelecer
Feb 17, 2019
137
44
Bosch is too clever for that. There software doesn't allow to run without a speed pulse, neither will it allow to run with the speed pulse in proportion to the motor speed.
Not sure what you mean by "neither will it allow to run with the speed pulse in proportion to the motor speed."
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
991
543
Northampton
No stl files,
I’m a old school engineer and make things from the material at hand hence one black pulley and one red, the drive belt is an elastic bootlace ;)

I managed to get a proper ride in late this afternoon, I’d planned for 25 miles but after 8 the heavens opened so I came home the shortest route making my ride only 13 miles , also the Aldi Speedo had stopped in the rain but it had done its job, confirming the 25kph on my Bosch display was actually 25mph :cool: I’d also recorded my 13 mile ride on Komoot and that said I’d covered 12.7miles.
It was a new experience riding around in the low 20s without too much effort and I’ll see how the battery holds out over the next few rides before deciding if this is a permanent modification.
just putting the sensor back in its original position and I’m legal again.

all in all a successful experiment
 

egroover

Esteemed Pedelecer
Aug 12, 2016
354
192
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UK
genius...but isnt the easiest solution the one I read that you glue the magnet to the inside of the left hand pedal arm (on the inside of the pedal) and reposition the sensor, like this
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
7,347
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West Sx RH
:cool:Good work Gringo .
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
991
543
Northampton
isnt the easiest solution the one I read that you glue the magnet to the inside of the left hand pedal arm (on the inside of the pedal) and reposition the sensor, like this
But what dose the speedo display with your method ?
You missed the point of my experiment, it was to see if it was possible to use the speed display set in kph but actually be travelling at mph while lifting the cutoff speed to 25mph.
 
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soundwave

Esteemed Pedelecer
May 23, 2015
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3,745
if it is working like that you could put a more powerful magnet on the spokes and remove the pulleys as wont work well in mud and rain lol.
 

Woosh

Trade Member
May 19, 2012
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if it is working like that you could put a more powerful magnet on the spokes and remove the pulleys as wont work well in mud and rain lol.
SW, would you ride at 25mph in mud and rain?
His idea is brilliant and Bosch can't say that he tampers with the bike's electronics.
 
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egroover

Esteemed Pedelecer
Aug 12, 2016
354
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But what dose the speedo display with your method ?
You missed the point of my experiment, it was to see if it was possible to use the speed display set in kph but actually be travelling at mph while lifting the cutoff speed to 25mph.
Yep, my method of course relies on fitting a £4.99 Aldi bike computer instead of some pulleys etc if you want know the accurate speed/distance
 

Nev

Esteemed Pedelecer
May 1, 2018
608
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His idea is brilliant and Bosch can't say that he tampers with the bike's electronics.
His idea is certainly very clever and I would never have thought of it. My concern however is that it is fairly noticeable. Any Police Officer seeing the alteration is going to know what is going on I would have thought, so this leads to the following questions.
1. If a Police Officer noticed this alteration what is the penalty, is it a fine, or is the bike taken away?
2. If the OP is involved in a serious accident while having the alteration fitted to the bike, is a prison sentence a possibility?
3. This question is not related to this clever adaption but is related to de-restricting pedelecs. A mate of mine asked me is it legal to use pedelecs that can be de-restricted by the use of a password on our roads? I told him I didn't think it was but I wasn't sure, does anyone know?
 

Woosh

Trade Member
May 19, 2012
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Southend on Sea
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I would have thought that everyone knows already that if you derestrict the bike, you risk having troubles with the law.
My view is not 'let's do it' because it does not tamper with the bike's electronics so who is to know? it's just a potentially reliable and more elegant way to derestrict your Bosch bike compared to other known methods.
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
991
543
Northampton
my method of course relies on fitting a £4.99 Aldi bike computer
That’s a coincidence, it was an Aldi £4.99 job that I’d used to confirm my Bosch display reading. I’d had it two days and it packed in the first time it got wet.
You’re singing the merits of Apple’s when I’m talking about oranges, that’s not an argument I’m going to get into :p:rolleyes:
 
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ebiker99

Pedelecer
Feb 17, 2019
137
44
His idea is certainly very clever and I would never have thought of it. My concern however is that it is fairly noticeable. Any Police Officer seeing the alteration is going to know what is going on I would have thought, so this leads to the following questions.
1. If a Police Officer noticed this alteration what is the penalty, is it a fine, or is the bike taken away?
2. If the OP is involved in a serious accident while having the alteration fitted to the bike, is a prison sentence a possibility?
3. This question is not related to this clever adaption but is related to de-restricting pedelecs. A mate of mine asked me is it legal to use pedelecs that can be de-restricted by the use of a password on our roads? I told him I didn't think it was but I wasn't sure, does anyone know?
Plus it would invalidate any cycle insurance and the user's driving license could be impacted.
 

flecc

Member
Oct 25, 2006
42,355
17,985
A mate of mine asked me is it legal to use pedelecs that can be de-restricted by the use of a password on our roads?
It is illegal to possess any fitted method under the rider's control that can increase the assist speed above 25 kph (15.5 mph), whether used or not.

Such a machine is no longer an EAPC (Electric Assist Pedal Cycle) in law. It becomes a motor vehicle with all that implies.
.
 
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