Cheap cadence computer for trainer

[DaveB]

I've got a dedicated **** bike for the trainer and want a computer to
measure cadence on it. But of course all the computers I see with
cadence are a bit expensive considering I only want one function.

So I was thinking of getting a cheap Huffy computer that does speed,
putting the spoke magnet on a crank, and the sensor on the frame
somewhere. Then running the cable up the downtube and as far along the
top tube as it will go. If the computer itself doesn't reach the bars it
doesn't matter, this bike will never leave the shed.

Then I configure the "wheel distance" to something that will give a
quickly recognisable value related to cadence (this is the bit I need to
give some more thought to). maybe I'll need a chart in front of the bike
that says xxkmh = yy rpm.

So what do people think? Anyone done anything similar?

Dave"cheapskate"B

 

[Walrus]

I know this isn't really your question...but you could buy an entry level cadence computer on eBay...like a Cateye Astrale 8 (which go for about $50 brand new in box). There's a heap for sale at the moment.

If the Huffy computer costs you $25(?)...then you add the parts and the effort to rig up a home-made cadence magnet...surely is worth another $25 to you for a reliable result?

 

[dej]

DaveB wrote:
> I've got a dedicated **** bike for the trainer and want a computer to
> measure cadence on it. But of course all the computers I see with
> cadence are a bit expensive considering I only want one function.
>
> So I was thinking of getting a cheap Huffy computer that does speed,
> putting the spoke magnet on a crank, and the sensor on the frame
> somewhere. Then running the cable up the downtube and as far along the
> top tube as it will go. If the computer itself doesn't reach the bars it
> doesn't matter, this bike will never leave the shed.
>
> Then I configure the "wheel distance" to something that will give a
> quickly recognisable value related to cadence (this is the bit I need to
> give some more thought to). maybe I'll need a chart in front of the bike
> that says xxkmh = yy rpm.
>
> So what do people think? Anyone done anything similar?
>
> Dave"cheapskate"B
gday dave,
bikepro in surrey hills were selling the sigma bc1600 with cadence
pretty cheap a while ago..not sure if they still have them though?
also i recently got a vetta rt77 from probike which has cadence etc (i
think it was $40) ?
the vetta quite simply is junk, but it'd do the job..

 

[Zebee Johnstone]

In aus.bicycle on Tue, 24 Oct 2006 16:20:42 +1000
DaveB <[email protected]> wrote:
>
> Then I configure the "wheel distance" to something that will give a
> quickly recognisable value related to cadence (this is the bit I need to
> give some more thought to). maybe I'll need a chart in front of the bike
> that says xxkmh = yy rpm.
>
> So what do people think? Anyone done anything similar?

I know someone who did it to measure RPM on their motorcycle...
Measured revs on the flywheel.

So yeah, can be done.

Zebee

 

[OzCableguy]

"DaveB" <[email protected]> wrote in message
news:[email protected]...
> I've got a dedicated **** bike for the trainer and want a computer to
> measure cadence on it. But of course all the computers I see with cadence
> are a bit expensive considering I only want one function.
>
>

Depends what you consider cheap. I use an Echowell Echo-F2 which can be had
for around $60.00 and usually comes with a long lead to reach the rear
wheel.
eg http://www.deanwoods.com.au/store/prod450.htm
Another one around that money is the Topeak Comp 140.
eg http://www.moruyabicycles.com.au/contents/en-uk/d31.html#p2100

--
www.ozcableguy.com
www.oztechnologies.com

 

[TimC]

On 2006-10-24, dej (aka Bruce)
was almost, but not quite, entirely unlike tea:
>
> DaveB wrote:
>> I've got a dedicated **** bike for the trainer and want a computer to
>> measure cadence on it. But of course all the computers I see with
>> cadence are a bit expensive considering I only want one function.
>>
>> So I was thinking of getting a cheap Huffy computer that does speed,

Eg., the $23 jobbie I found from goldcross during one of their regular
sales?

>> putting the spoke magnet on a crank, and the sensor on the frame
>> somewhere. Then running the cable up the downtube and as far along the
>> top tube as it will go. If the computer itself doesn't reach the bars it
>> doesn't matter, this bike will never leave the shed.
>>
>> Then I configure the "wheel distance" to something that will give a
>> quickly recognisable value related to cadence (this is the bit I need to
>> give some more thought to). maybe I'll need a chart in front of the bike
>> that says xxkmh = yy rpm.

Recall you can set the wheel circumference to some distance in
millimetres? So a 700C tire comes pretty darned close to 2000mm?

I haven't tested this, but the equations seem to call (and I'm not
going to show my working, because my working is dodgy for this
distance to be set to 16667mm to give an exact rpm figure when looking
at the km/h display of the speedo.

Since it is most likely that your computer will not be able to accept
a fake wheel of this size (a 200inch wheel???), you'll have to bring
that down to 1667mm -- ie, a 20inch wheel -- that's not overly unusual
now, is it?

OK, so when you are pedalling at 90rpm, the display will read 9.0km/h,
ie, a factor of 10 out -- nice and easy when you are doing 104% of
your maximum heartrate. Just make sure you don't pedal slower than
30rpm, when the display reads 3.0km/h, and cuts out

> bikepro in surrey hills were selling the sigma bc1600 with cadence
> pretty cheap a while ago..not sure if they still have them though?
> also i recently got a vetta rt77 from probike which has cadence etc (i
> think it was $40) ?
> the vetta quite simply is junk, but it'd do the job..

I got my BC1600 from a bike shop down the bad end of chapel street
(south), on a perpendicular road just a bit off chapel -- "melbourne
bicycle store", perhaps? $50-$60. Be careful -- the cadence is only
an optional accessory -- and some people may well try to sell you one
without the cadence kit.

--
TimC
Always carry a short length of fibre-optic cable. If you get lost,
then you can drop it on the ground, wait ten minutes, and ask the
backhoe operator how to get back to civilization. -- Mike Andrews in NANAE

 

[DaveB]

TimC wrote:
>
> Recall you can set the wheel circumference to some distance in
> millimetres? So a 700C tire comes pretty darned close to 2000mm?
>
> I haven't tested this, but the equations seem to call (and I'm not
> going to show my working, because my working is dodgy for this
> distance to be set to 16667mm to give an exact rpm figure when looking
> at the km/h display of the speedo.
>
> Since it is most likely that your computer will not be able to accept
> a fake wheel of this size (a 200inch wheel???), you'll have to bring
> that down to 1667mm -- ie, a 20inch wheel -- that's not overly unusual
> now, is it?
>

On ya Tim, nice to see all that book lernin' doing some good.

DaveB

 

[ritcho]

[snip]

Recall you can set the wheel circumference to some distance in
millimetres? So a 700C tire comes pretty darned close to 2000mm?

I haven't tested this, but the equations seem to call (and I'm not
going to show my working, because my working is dodgy for this
distance to be set to 16667mm to give an exact rpm figure when looking
at the km/h display of the speedo.

[snip]
--
TimC
Always carry a short length of fibre-optic cable. If you get lost,
then you can drop it on the ground, wait ten minutes, and ask the
backhoe operator how to get back to civilization. -- Mike Andrews in NANAE

Umm, I think the gearing fits in there somewhere... if you have a fixie or singlespeed, you won't need the cadence kit.

Ritch

 

[DaveB]

ritcho wrote:
>
> Umm, I think the gearing fits in there somewhere...

No the gearing won't affect it because I'm measuring at the pedal not
the rear wheel. However, you do raise doubts in my head so even though
Tim makes sense I'll be interested to see what actually happens when I
set it up (the Huffy comp comes off the MTB tomorrow night).

DaveB

 

[Rory Williams]

TimC wrote:
>
> Recall you can set the wheel circumference to some distance in
> millimetres? So a 700C tire comes pretty darned close to 2000mm?
>
> I haven't tested this, but the equations seem to call (and I'm not
> going to show my working, because my working is dodgy for this
> distance to be set to 16667mm to give an exact rpm figure when looking
> at the km/h display of the speedo.
>
> Since it is most likely that your computer will not be able to accept
> a fake wheel of this size (a 200inch wheel???), you'll have to bring
> that down to 1667mm -- ie, a 20inch wheel -- that's not overly unusual
> now, is it?
>

On ya Tim, nice to see all that book lernin' doing some good.

DaveB

Beat me to it. I did the sum a while back for the same reason but never put it into practice

I was going to use a circumference of 1666.

At this setting a "speed" of 1.0km/hr represents 10 rpm 8.5 km/hr = 85 rpm ect. (to 1 decimal place)

I wasn't sure that my computer would accept a 5 figure circumference

RoryW

 

[DaveB]

TimC wrote:
>
> Since it is most likely that your computer will not be able to accept
> a fake wheel of this size (a 200inch wheel???), you'll have to bring
> that down to 1667mm -- ie, a 20inch wheel -- that's not overly unusual
> now, is it?
>
> OK, so when you are pedalling at 90rpm, the display will read 9.0km/h,
> ie, a factor of 10 out -- nice and easy when you are doing 104% of
> your maximum heartrate. Just make sure you don't pedal slower than
> 30rpm, when the display reads 3.0km/h, and cuts out

Tim you're a marvel. Just finished setting it up and it's a winner.
Trickiest part was attaching the spoke magnet to the crank but there's
nothing you can't fix with gaffa tape and a tube of silicon sealant.
Total cost = $0 because I had an old computer to reuse.

DaveB