Tachometer

GoldenMotor.com

Coval_PL

New Member
Jul 28, 2009
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Gdynia/Poland
I have an idea, that i want to try. I want to use standard cyclo-computer and place his sensor near magneto. The sensor is a magnetic sensitive element, which has 2 little steel "leaves" that contact when the magnet mounted on the bicycle's weel goes by. I'm curious if it's possible to set computer so it will show approximates value of engine turns. I have to calculate how to set "wheel size" to get good results.
I don't know if this device can record impulse so fast as magneto turns. If it could handle it it will be cheapest way to measure RPM's :)

zpt
 

Coval_PL

New Member
Jul 28, 2009
57
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0
Gdynia/Poland
I made a quick calculation and if 1000RMP would be tepresented by 10km/h, the "wheel size" in cyclocomputer must be set to around 8cm. (wheel size setting resolution is 1cm). I hope this little computer can be set to this value and hold this frequency.

My calculation:
10km/h = 2,78m/s
1000 Rounds/Min=16,66 Rounds/Sec
so: 2,78ms / 16,66 R/S = 0,1669 = 16,69cm

Magneto has 2 poles so it makes 2 tacts per round, that mean 16,69cm mus be divided by 2. It gives result around 8cm (exacly 8,35cm).

The same calculation has to be done for US miles/h.
Am I right?
 
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Coval_PL

New Member
Jul 28, 2009
57
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0
Gdynia/Poland
I have bought two sets of this cyclocomputer linked in my previous post. It looks great. I would be happy MBiker if this could be works as RPM meter. I'll have both of them on my bike: one for speed and one for RPMs :D
Unfortunatelly I have to wait allmost 2 weeks becouse i just started my vacation :(
 

restapukin

New Member
Jul 22, 2009
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australia
Got a harmonica? or guitar pitch-pipes?

when an engine is running in the midrange @ 3,300 it will be in-tune with the A note on a musical instrument.....

mmm... but 6,600 revs is also an 'A' ...as is 1,650rpm and 825rpm...

once upon a time you could buy a "tyne tachometer", they looked like a metal dreadlock comb.... you mounted 'em to the chassis somewhere and watched for which comb prong or tyne was vibrating in tune with the motor....
 

Norman

LORD VADER Moderator
Jan 16, 2008
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pampa texas
Log On
this wil get you to american power sports I think but you can google the name and look for tachs digatron 30 or 40 series they are not cheap!
here is a tach and head temp gauge from American power sports GoKart racing
its not cheap but a very rugged gauge I have one on my racing kart. I haven't raced the kart in a couple of years so I might take it off the kart and put it on one of my bikes this tach will work on either 2 or 4 stroke engines it has a head temp sensor and a lot of features it will record your highest rpm and head temp etc. I know they cost more than the bike engine just wanted to let you all know what is out there. Turk brothers also sells them google racing karts you might be able to find this gauge for less money if you want to do some searching.
Norman
 

MikeJ

New Member
May 3, 2009
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Colorado Springs
Here is another site: SenDEC Products Group - Home.

Look at their Inductive Meters (Surface Mount). I ordered one today; the cost to my doorstep (product and shipping) is less than $48. A picture shows you wrap the pickup wire around the sparkplug wire. There is no stated voltage source. It appears that the inductive pickup wire also supplies enough energy to power the internal microcircuit. With velcro tape, I plan on making mine portable from one bike to another. They claim the meter is good for up to 8,000 rpm.