Wilsons Sandbox

At 07:29 AM 6/30/2000 -0500, Michael Campbell (EUS) wrote:

>Hi All, > >My wife has an A3 and is tired of me telling her that she needs to go faster >because her speedo is at least 5mph slow. Is there a way to calibrate it on >the speedo internals, or, is there a calibration 'gear drive' or something I >can put at one end of the cable to adjust the speedo? > >Thanks for any input! >Mike Campbell >Lynchburg, VA >A1

Not really... Unfortunately. Our speedo works directly off the cable, not geared. There is a viscous spin chamber that spins up the needle a certain angular displacement based on the RPM's of the cable. It may be possible to get a better matched viscous liquid in there but for 5-10% its not worth it. The unit is sealed and you can't open it easily without destroying it. However, you can completely remove the Speedo Needle and spin chamber, put in a rotational tach with programmable-digital readout. Again not worth the 5-10% but it would be pretty trick. But then again for $30 you can install a bike computer, for a couple hundred you can install a GPS receiver and for about $600 you can install an always on radar. That would be fun just to watch detector owners spaz out when you are near. You buy... I'll fly. It can be done, we have the technology, I just don't have the money. LaterZ Dash

At 11:31 AM 6/30/2000 -0700, Tom Myers wrote:

>>Our speedo works directly off the cable, not geared. There is a viscous >>spin chamber that spins up the needle a certain angular displacement based >>on the RPM's of the cable. > >Are you sure it's viscous? All the MC speedos I've seen are electrical >where a coil or magnet spins and the guage simply "reads" the voltage >generated. > >Accuracy of a viscous drive might be drastically affected by temperature. > >Tom

Hi Tom, Most certainly not electrical. Mark brought up an interesting point off list and that was "magnetic reluctance" Wasn't quite sure if he was talking about magnetic field due to current in a coil, thus inductance or a mechanical device of carefully designed magnets to attract and repel along the circular path of the needle shaft (certainly feasible). I had my instrument cluster completely apart the other night. There is a mystery thingy that is directly attached to the cable housing. When I moved the needle by hand I watched that thing in action. It is like two concentric drums, only really short. There is obviously a spring inside to keep the needle at zero. It returned really slowly when actuated by hand. Thus a time lag between cable RPM and needle position. I assumed it was a liquid. The mystery thingy looks like a miniature torque converter and it behaves as if it had a fluid inside. No wires or coils anywhere near it. Very much unlike the Tach and Temp shafts in the same cluster. I would like to find one and dissect it just to know, but I'll have to do some digging. Steve Pye, you wouldn't happen to have the Speedo on the old A1 would ya? Perhaps not a fluid but a grease or something like a silicon oil. Some silicon oils have a huge range of near constant viscosity. But yes I agree that one would expect a large temperature effect if it is indeed a fluid.... LaterZ Dash always searching for the truth.... the truth is out there....

Bigger tires [knobbies] corrected mine. I'm 1/10 off in 5 miles with Pirelli mt-21's or Kenda 270's. Hate the tires but the speedo works. Actually I really like the Kendas especially with the free speedo calibration. DAngus A-11 -----Original Message----- From: Dave Leslie [mailto:les123@...] Sent: Friday, June 30, 2000 8:47 AM To: DSN_klr650@egroups.com Subject: [DSN_klr650] Re: speedo calibration Hi Mike, Never heard of a correction for the stock speedo. Add-on bicycle speedo seems like the best solution mentioned on the list in the past. Not too many $, installation pretty straightforward. Dave Leslie A14 Richmond --- In DSN_klr650@egroups.com, "Michael Campbell (EUS)" wrote:

> Hi All, > > My wife has an A3 and is tired of me telling her that she needs to

go faster

> because her speedo is at least 5mph slow. Is there a way to

calibrate it on

> the speedo internals, or, is there a calibration 'gear drive' or

something I

> can put at one end of the cable to adjust the speedo? > > Thanks for any input! > Mike Campbell > Lynchburg, VA > A1

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Dash wrote in reference to the thread about speedo calibration:

> Hi Tom, > > Most certainly not electrical. Mark brought up an interesting

point off

> list and that was "magnetic reluctance" Wasn't quite sure if

he was

> talking about magnetic field due to current in a coil, thus

inductance or a

> mechanical device of carefully designed magnets to attract and

repel along

> the circular path of the needle shaft (certainly feasible). > > I had my instrument cluster completely apart the other night.

There is a

> mystery thingy that is directly attached to the cable housing.

When I

> moved the needle by hand I watched that thing in action. It is

like two

> concentric drums, only really short. There is obviously a

spring inside to

> keep the needle at zero. It returned really slowly when

actuated by

> hand. Thus a time lag between cable RPM and needle position.

I assumed it

> was a liquid. The mystery thingy looks like a miniature torque

converter

> and it behaves as if it had a fluid inside. No wires or coils

anywhere

> near it. Very much unlike the Tach and Temp shafts in the same

cluster.

> > I would like to find one and dissect it just to know, but I'll

have to do

> some digging. Steve Pye, you wouldn't happen to have the

Speedo on the old

> A1 would ya? > > Perhaps not a fluid but a grease or something like a silicon

oil. Some

> silicon oils have a huge range of near constant viscosity. But

yes I agree

> that one would expect a large temperature effect if it is

indeed a fluid....

> > LaterZ > Dash > always searching for the truth.... the truth is out there....

The drum is an "eddy current" device. On the end of the speedo cable is a small circular magnet; when the magnet spins, the field drags the drum around with it, causing the needle to move. They aren't mechanically connected: there's no fluid or connection between the input and the needle - just a magnetic field. Most speedos are calibrated by changing the preload of the spring you see in there, but unfortunately the KLR instrument can't be done that way due to the spring end being crimped in place to the frame. It is possible to change the KLR's calibration by prying the needle off its axle and repositioning it higher or lower if you know by how much to move it - an exercise in itself. This isn't easy and potentially can ruin your speedo if done clumsily, so I won't broadcast a "How-To" to the List; anybody who feels they have to do it, contact me off-line. Tom Bowman Atlanta A14 "Stella" "The truth is out there.......WAAAAY out there."

-----Original Message----- From: Dash Weeks To: Tom Myers ; DSN_klr650@egroups.com DSN_klr650@egroups.com> Date: Friday, June 30, 2000 4:53 PM

>I would like to find one and dissect it just to know, but I'll have to do >some digging. Steve Pye, you wouldn't happen to have the Speedo on the old >A1 would ya? >LaterZ >Dash >always searching for the truth.... the truth is out there....

Sorry Dash, The complete instrument package from the A1 now resides on my A7. The first owner of the A7 sort of, umm....badly flattened the original parts!! Steve

Tom, Thank you soooooo much. The curiosity was killing me, and I was gonna tear into my speedo this afternoon. It makes much more sense to me that it is magnetic rather than electrical, or worse fluid. It just behaved like a fluid. Its terrible to think of what I almost did... but inquiring minds HAVE to know.... Reminds me of the "you know you're and engineer if" list that circulates every so often. LaterZ Dash

>The drum is an "eddy current" device. On the end of the speedo >cable is a small circular magnet; when the magnet spins, the >field drags the drum around with it, causing the needle to move. >They aren't mechanically connected: there's no fluid or >connection between the input and the needle - just a magnetic >field. > >Most speedos are calibrated by changing the preload of the spring >you see in there, but unfortunately the KLR instrument can't be >done that way due to the spring end being crimped in place to the >frame. It is possible to change the KLR's calibration by prying >the needle off its axle and repositioning it higher or lower if >you know by how much to move it - an exercise in itself. This >isn't easy and potentially can ruin your speedo if done clumsily, >so I won't broadcast a "How-To" to the List; anybody who feels >they have to do it, contact me off-line. > >Tom Bowman >Atlanta >A14 "Stella" >"The truth is out there.......WAAAAY out there."

> > >Sorry Dash, >The complete instrument package from the A1 now resides on my A7. The first >owner of the A7 sort of, umm....badly flattened the original parts!! >Steve

No Problem Steve, Tow Bowman answered my question. Mark had it right as well. Good thing too. I hate to think of what I was capable of in there. LaterZ Dash

is it really worth it ? There is a hell of a lot of uncertainty associated with the type of speedo used on motorcycles (or bicycles for that matter). Even if you has incredible accuracy set to a calibrated measured mile etc the design has very poor precision and as such cannot be relied upon. Many factors can alter the effective diameter of your front wheel as you are riding and these can change your actual registered MPH. 1) Turning corners alters the effective diameter of the front (If it didnt leaning would not work). This can be a dramatic change yielding apparent 4-5MPH speed increses when leaning hard over (such as in superbike racing) 2) Bouncing over road imperfections causes errors as the wheel fails to track the surface 3) Centrifugal force increases the Diameter 4) Tyre pressure can change the effective diameter 5) Fuel load and or body position can change the effective diameter of the front wheel by compressing the fron tyre. 6) Temperature, Air pressure, tyre wear, tyre type etc etc all can change the diameter of that front wheel. How do I know this ? My job involves the calculation of measurement uncertainties and I was once used as an expert witness in a court case over a Cycling time trial record. The professional body claimed a 10 mile record did not count due to the course being short.(they measure them using a bicycle with digital computer). I went onto to prove that by manipulating many of the factors above you could effectively measure that same course too long or too short (cant remember the actual details). I use a GPS and can do not see a consistent variation between the KLR speedo and the GPS. The KLR speedo always reads high (about 3-10 MPH depending upon speed and all of the other factors)but I have not taken much notice. Regards Mark --- Dash Weeks wrote:

> Tom, > > Thank you soooooo much. The curiosity was killing > me, and I was gonna tear > into my speedo this afternoon. > It makes much more sense to me that it is magnetic > rather than electrical, > or worse fluid. It just behaved like a fluid. > > Its terrible to think of what I almost did... but > inquiring minds HAVE to > know.... > > Reminds me of the "you know you're and engineer if" > list that circulates > every so often. > > LaterZ > Dash > > > > > >The drum is an "eddy current" device. On the end of > the speedo > >cable is a small circular magnet; when the magnet > spins, the > >field drags the drum around with it, causing the > needle to move. > >They aren't mechanically connected: there's no > fluid or > >connection between the input and the needle - just > a magnetic > >field. > > > >Most speedos are calibrated by changing the preload > of the spring > >you see in there, but unfortunately the KLR > instrument can't be > >done that way due to the spring end being crimped > in place to the > >frame. It is possible to change the KLR's > calibration by prying > >the needle off its axle and repositioning it higher > or lower if > >you know by how much to move it - an exercise in > itself. This > >isn't easy and potentially can ruin your speedo if > done clumsily, > >so I won't broadcast a "How-To" to the List; > anybody who feels > >they have to do it, contact me off-line. > > > >Tom Bowman > >Atlanta > >A14 "Stella" > >"The truth is out there.......WAAAAY out there." > >

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At 11:46 AM 7/3/00 -0700, Mark King wrote:

>is it really worth it ? > >There is a hell of a lot of uncertainty associated >with the type of speedo used on motorcycles (or >bicycles for that matter).

I'm sure that the points made in this mail are true and valuable, but still I have found it very easy to calibrate a front wheel circumfrence so that my add-on bicycle speedo agrees with GPS within 1-2% under all normal conditions. To point out that this speedo error is, I'm convinced, intentional on the part of the manufacturers, I'll add that my Super Sherpa, in which all of the speedo/odometer functions are pure digital pulse counters, has the odometer - as usual - correct, but the speedo - also as usual - reads 8-10% high. Since this depends only on a divide constant in the little computer, it is obviously not an mistake. This used to be true of automobiles as well...possibly a characteristic of magnetic drag speedos, though I doubt it...but modern Japanese cars are dead on on the speedos at all legal speeds vs. GPS. Hugh Stout