magnets?

[Mikeeboy]

I have bought a concept 2 model b,really cheap do dont mind putting in the cleaning/repair effort but my monitor works, but didnt work when rowing,kind of worked it out the its magnet based,so strapped on 1 magnet to see if its that and it foes work but is miles out on metres rowed, are there magnets you can buy to replace to put on the flywheel??? thanks in advance
mike

[Citroen]

You need the number of magnets for your flywheel which is based on whether you have a PM2, PM3, PM4 or PM5

There's documentation at https://www.concept2.com/service/monitors/pm5 assuming you have a PM5.

[JaapvanE]

Magnet placement is quite a difficult task, and a PM* is quite picky what it accepts as data as C2 is quite good at placing them. I don't think people can do this aftermarket and get good results.

[Mikeeboy]

So even if i upgraded to a pm5 it wont help with the magnets???

[c2jonw]

The model B has three magnets pressed flush into holes in the flywheel on the sprocket side of the flywheel. They are about 1/10" in diameter and equally spaced about 2" from the center of the flywheel. Locate them and give them a good wipe down with solvent. That may fix it. If not, last I knew you could get the magnets from C2 and replacing them is not difficult. They're a bit fragile and polarity is important. Since 'you are getting data with one magnet it would seem your pickup is ok. Also check the clearance between the flywheel and the pickup- it should be around 1/16-1/8". Once you have the machine working with the current monitor it will work with any C2 rower monitor if set to the proper model machine. Good Luck with it- Model Bs are the workhorse that put Concept2 on the map....

[JaapvanE]

A Model D has three magnets, and the PM5 can be told to consider something a model D. Issue is getting the magnets well placed (evenly spaced) on the flywheel and maintaining balance in that flywheel.

I am one of the developers of OpenRowingMonitor (basically the open source version of the PM5), and we notice that placing magnets on OpenErgo (home made model B's ) is a bit flaky. Some do it extremely well and are placing them perfectly getting great results, others are too unprecise and have flywheel unbalance and less perfect data. OpenRowingMonitor can handle the data regardless, but at the cost of some precision when magnets aren't decently aligned or the flywheel is unbalanced. So I'm always a bit hesitant to advice people to stick on (extra) magnets without manufacturers guidance.

I know that the PM5 is accustomed to the high quality placement of C2, so you might be able to fix it, but you could end with dissappointment. You could contact C2 directly and ask them for help. Their service is superb, even for older machines like the Model B. I must say each time I contacted them, I was not disappointed by them in any way.

edit: as John says: the holes in a model B help a lot in placing them. And cleaning helps as well....

[c2jonw]

A Model D has three magnets,

Nope- Models A,B, and C use 3 small rare earth magnets imbedded in the flywheel. Models D,E, SkiErg and BikeErg have a single donut shaped magnet that has 12 poles- 6 positive and 6 negative.

[JaapvanE]

A Model D has three magnets,

Nope- Models A,B, and C use 3 small rare earth magnets imbedded in the flywheel. Models D,E, SkiErg and BikeErg have a single donut shaped magnet that has 12 poles- 6 positive and 6 negative.

Thanks for the correction John!

[Mikeeboy]

Thanks guys that gives me some scope, i can see the places/magnets you are talking about and will give them a jolly good clean tomorrow, will keep you posted
thanks
mike

[c2jonw]

And just to be accurate- the Model A originally came with an analog bicycle speedometer that basically just counted flywheel revolutions. The first PM was developed for the Model B and was made retrofittable to a Model A using a plastic disc with three magnets which attached to the hub of the flywheel.

[Carl Watts]

Three magnets in the flywheel they are imperial so they are 3/16" diameter.

If the nickel coating on them gets compromised due to corrosion they disintegrate.

They can be replaced with 3mm neodymium magnets and you just accurately drill out the holes with a brand new 3mm drill and just Loctite the new magnets in.

Technically they are polarity dependant but as long as you feed them in all the same way it will work, the difference is the pulse from them goes negative if you get it wrong instead of positive but the pulse is amplified and goes through a Schmitt trigger to get a nice square wave that's fed into the micro.

If you pull the handle and the monitor turns on it indicates at least one magnet is working, however the monitor needs all three to be working to be able to show you are rowing.

[JaapvanE]

The first PM was developed for the Model B

And what a combo it was. Spend a lot of time on the model B, competing against teammates. We were supposed to use the rower just to warm up, but it always turned into a competition somehow.

[jamesg]

single donut shaped magnet that has 12 poles- 6 positive and 6 negative.

Presumably the circuitry reads 12 impulses per turn of the wheel.

[Carl Watts]

single donut shaped magnet that has 12 poles- 6 positive and 6 negative.

Presumably the circuitry reads 12 impulses per turn of the wheel.

Apparently only 6 by someone that's taken a deeper dive than me into it.

The pickup transformer is large, probably spans more than one magnet so it runs in pairs. Doesn't really matter 6 is better than 3 and all possible with faster electronics.

Never had the electronics on the pickup fail its always the cable that fails. the cable should just plug in to the board making it an easy fix.

[Mikeeboy]

Your point about it only ever been the cable, thst eas my first thought but, there was a kink,snick in the cable do i cut and spliced it still mnot working so put a random magnet on the fly wheel and got a reading which leads me to think it must be magnets ????