What you need if you want to make a tachometer is a cyclocomputer with
cadence feature. this feature is the only function of a cyclometer that
will serve as a tach, as it measures rotational speed at the bike's
crank. You might be able to calculate rpm based on the distance
feature, whereby you program in the exact diameter of the  imaginariy
"wheel diameter" of the spinning magnet and the results serve as an
odometer function.

Only the more expensive cyclocomputers have the cadence function, but
my wife just installed one from Axiom (sold both at bikenashbar.com and
performancebike.com, I believe) and I think she got it for about $20.
Search the sites for axiom 8C and see if that doesn't turn up something.

It would be easy enough to use the hardwire version, as the dimensions
of the wire are very small.

When we both had transmitting computers a few years back, if we got
side by side on the road the units tended to receive each other's data.

Remember that the transmitting version has to have a battery on both
ends, not just the display end.

And remember too that there needs to be NO MORE than 3mm between the
rotating magnet and the stationery pickup.

Hope this helps,

Jim

PS if you're into bikes anyway, you might be pleased to know that the
Park tool for removing old fashioned french-style headsets will also
tension the belt on a vw diesel!

On Thursday, November 6, 2003, at 04:56 PM, Joe Federici wrote:

> Can I  why someone wants to do this.
>
> I've used a few different brands on my bikes and find cateye's to be
> the best for what it's worth.
>
> JFF
>
>> I have one on a road bike that is "radio" signal so it can have some
>> "stuff"
>> slightly in the way but not much and the distance can't be more than
>> about
>> 30" from sender to head unit.
>>
>>
>>
>> Bob Stevens
>>
>> http://groups.msn.com/BobsPhotoShare
>> http://groups.yahoo.com/group/tiico
>>
>>
>> On Thursday 06 November 2003 05:53 pm, Mark Tuovinen wrote:
>>>  Some of the bike tachs are wireless,but you are still limited to a
>> certain
>>>  distance from the sender on the wheel.
>>
>> I think the wireless ones might be infrared, so you have to have a
>> clear
>> line-of-sight between the sender and the head.
>>
>> _________________________________________________________________
>> Is your computer infected with a virus?  Find out with a FREE
>> computer virus
>> scan from McAfee.  Take the FreeScan now!
>> http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963
>