Model C flywheel magnets/pickup question

[batex]

Hoping someone can help me out. I'm searching for a picture of the back side of a Model C flywheel to understand the magnet configuration. I'm beginning to think the Model C erg I have has been modified from original configuration. Here's why. It originally came with a PM2, but the it would never register correctly on the display. When I took out the pickup, the sensor had been snapped off. Interesting.... Well, I recently bought a used PM3 from ebay and also a brand new pickup directly from Concept 2. After installing the new pickup and giving it a whirl, well what do you know...the flywheel immediately locks up. Then I pulled harder and snapped off the sensor from the new pickup I had just installed. There were significant clearance issues.

My flywheel as a set of three magnets epoxied together to form a 1" square that protrudes from the surface of the flywheel by about 1/4". I'm beginning to think this cannot be correct. I had to put a 3/16 spacer when installing the pickup after I glued it back together just to provide enough clearance. It works, but split times are in the 5-6 minute range. My daughter who rowed in high school and college immediately said "dad, there's something wrong with the display' She should know as she's put probably hundreds of hours both on ergs and on the water....

I've attached pictures below if that helps the forum diagnose my issue. I would love to see a picture of what a Model C flywheel should look like on the inside surface.

Many thanks!

[Carl Watts]

Wow thats the worst repair job I have ever seen.

You see those other two 3/16 inch magnets embedded in the flywheel ? All three are supposed to look like that. That epoxy magnet mess needs to be removed and I would replace all 3 magnets with Neodymium magnets of the same size.

The magnets are supposed to be flush with the flywheel or poke out 0.5mm max. That configuration is going to smash your sensor off.

If your not in the USA and your country is Metric like most of the world, punch them all out and drill the holes to 3mm and put in three 3mmx4mm magnets or 3mmx3mm magnets.

Try the magnets first before using some Loctite or superglue to hold them in permanently, if it doesn't work, take them out and reverse the fitment to change the poles. All 3 need to be facing one way or the other. Put the magnets together to form a "Stick" and feed them in from one side.

[jamesg]

Put the magnets together to form a "Stick" and feed them in from one side.

Genius

[batex]

Carl,
Thank you! Yes, I suspected this was a poor repair job and is what caused me to break my brand new sensor. However, this is the only machine I've ever taken apart and since I didn't have anything to compare to, I needed that confirmation. So I greatly appreciate your help. I'll plan to knock off the repair magnets and follow your advise. Will post back here with updates and resolution.
Thanks again!

[batex]

Quick additional question. Is there a preferred magnet size if I were to replace all three? Any advantage to going to a slightly larger diameter magnet, or should I stick with the same size?

BTW, I'm in the US, Asheville, NC.

Thanks

[mict450]

Wow thats the worst repair job I have ever seen.

Idiocy has no boundaries!

[Carl Watts]

Sorry I think the OEM magnet size is 3/32 inch or about 2.4mm not 3/16 inch. Definitely less than 3.0mm anyway.

[faach1]

Quick additional question. Is there a preferred magnet size if I were to replace all three? Any advantage to going to a slightly larger diameter magnet, or should I stick with the same size?

BTW, I'm in the US, Asheville, NC.

Thanks

I think a different size magnet would affect the monitor’s readings, may be wrong though.

[batex]

Problem solved! I took a chisel and chipped off the magnet and epoxy conglomeration, reassembled and all appears to be working fine. It's not the prettiest job, but fortunately, all three original magnets were there. I have no idea why the modification was done, but oh well, it works and the used PM3 I just purchased off Ebay appears to work fine and is reporting reasonable split times.

Thanks to all who responded.

[mict450]

Glad you got your machine up & running.

[Carl Watts]

Quick additional question. Is there a preferred magnet size if I were to replace all three? Any advantage to going to a slightly larger diameter magnet, or should I stick with the same size?

BTW, I'm in the US, Asheville, NC.

Thanks

I think a different size magnet would affect the monitor’s readings, may be wrong though.

No you can change the magnet size to 3mm with no issues. You need an oscilloscope to really see whats going on with the Tach signal. you connect the scope directly to the end of the cable at the right angle connector and row, no monitor required.