thoughts on this used C2 (and meaning of numbers)

[Carl Watts]

Made my own swivel bush from a bar of solid extruded phosphorous bronze bearing material, its a "lasts a lifetime" version.

[Ombrax]

My bushing has a slot, it was bought new last year.
Maybe they come with a slot for some time.

That's interesting.

My Model C came with a "no slot" bushing. I looked at it when I wanted to donate it to the Model E at my gym, but I didn't want to go through the hassle of disconnecting the chains, so I ordered a replacement for the gym erg from C2.

I assumed that all other new ones came with the slot, but based on what you guys are saying, they must have switched over for the production configuration. (Obviously the Model C was made a long time ago, so it isn't surprising that a few things have changed since then.)

[JaapvanE]

Made my own swivel bush from a bar of solid extruded phosphorous bronze bearing material, its a "lasts a lifetime" version.

Without any design knowledge, but with a decent mechanical engineering background. This part is desgined to wear out be easily replaceable. Probably (my interpretation) to prevent wear and tear in a place that is much harder ro replace (like the chain end).

It is a bit like a fuse: you have a deliberate weak element in your design, where degradation is easily noticed and replacement is trivial, to protect weaker parts in the installation that are hard to inspect and replace.

You just removed that deliberate weakness....

[ecrow]

Made my own swivel bush from a bar of solid extruded phosphorous bronze bearing material, its a "lasts a lifetime" version.

Without any design knowledge, but with a decent mechanical engineering background. This part is desgined to wear out be easily replaceable. Probably (my interpretation) to prevent wear and tear in a place that is much harder ro replace (like the chain end).

It is a bit like a fuse: you have a deliberate weak element in your design, where degradation is easily noticed and replacement is trivial, to protect weaker parts in the installation that are hard to inspect and replace.

You just removed that deliberate weakness....

so its literally designed to be the weakest link in the chain....

[JaapvanE]

so its literally designed to be the weakest link in the chain....

I think so. I'm one of those people who first wants to know WHY it was designed in a specific manner, and only then starts modifying stuff.

I always look at things like this from an engineering perspective. In design, somebody had to argue with the big boss to add an additional part to the machine, adding cost and manufacturing time to the product, as well as potential supply chain issues and adding yet another part to the inventory. Still they stepped away from the cheapest and simplest design possible (i.e. the extra part argument was won), which implies it was done to mitigate a specific issue worth all the hassle. If C2 wanted a tougher more robust design, they simply made the connector heavier or used a tougher material. That would have saved time, cost and inventory. They went for a very distinct material that is softer, and a shape that falls off when worn out.

When I look at it, it's function seems to be to provide a second layer of connection together with the hole where the handle attaches. That chain end in itself is pretty hard material, where the bushing is much softer and it seems to be designed to accept a lot of wear and fall off when worn out. It might protect the hole from wearing out. Or it allows the handle connector from wearing in better, providing a much better fit. So replacing it with a harder material might increase the time untill it wears out, but it might also increase the stress on the end of the chain or reduce the fit in the long run.

[Willy.VdW]

Without any design knowledge, but with a decent mechanical engineering background. This part is desgined to wear out be easily replaceable. Probably (my interpretation) to prevent wear and tear in a place that is much harder ro replace (like the chain end).

Yes, I believe this is indeed the case!
Not only is replacing the bushing easy, it is also cost-effective.

[Willy.VdW]

In my opinion, the bushing as it is developed by Concept2 is a good solution.

[Carl Watts]

Well sorry you guys would be wrong.

Its designed to be a bearing surface, not just wear out and fail. The factory one is a sintered material, that is it is made by compressing the material a bit like a fish tank aerator but its compressed harder. This is a very inconsistent technique with very poor strength compared to an extrusion, you can have a bearing that lasts for years or if you are putting in power it last for months. You also couldn't rotate the C2 one before it broke to make it last longer because it was so soft it deformed into the holes of the stainless jamming it.

The C2 bearing does last longer with a run in period as this allows the load to be more evenly distributed but if you fit a new one you will notice it has point contact with the U bolt.

I machined one up in the lathe in a two part process, the second involved putting it in a special tool made to machine the handle contact point as a better match .i.e. its a match for both the diameter of the U bolt and the radius its been bent to.

The only disadvantage is it goes a little green if you sweat on it, probably the copper content of the bearing but you could probably clear coat it.

The new Concept 2 has the advantage is that its quick to replace now and its cheap, you just keep replacing it. They changed the design and put a slot in it because your average Joe cannot even remove the chain to fit the old design.

Pictures below of the bearing and what happens if breaks and you don't replace it. Stainless on stainless is really bad as a bearing material.

[JaapvanE]

Its designed to be a bearing surface, not just wear out and fail.

The C2 bearing does last longer with a run in period as this allows the load to be more evenly distributed but if you fit a new one you will notice it has point contact with the U bolt.

So basically it is there to protect the stainless part from wearing out earlier then the rest of the chain.

I machined one up in the lathe in a two part process, the second involved putting it in a special tool made to machine the handle contact point as a better match .i.e. its a match for both the diameter of the U bolt and the radius its been bent to.

So in a sense, you fitted it better, reducing the need to wear it in like the original one. But when you use harder material, dont you get the same effects of stainless-on-stainless (for example, wearing out the U of the handle or still wearing out the bushing fast)? I'm not questioning your craftmanship, but I wonder why C2 opted for a softer bushing. In essence, the tools you used ate probably also available to C2. So why introduce a softer part introducing more service calls for replacement?

Pictures below of the bearing and what happens if breaks and you don't replace it. Stainless on stainless is really bad as a bearing material.

That bottom part is actually quite worn out and nearly broken? I hope it was used by 300 pound Gorilla's for over 100.000 kilometers? I do not expect that hefty damage on a chain that gets a 500N to 700N pull quickly.

[Slidewinder]

In my opinion, the bushing as it is developed by Concept2 is a good solution.

Obviously, you like the inconvenience of sending off for a replacement bushing because the one on the machine broke. That is much better than having the bushing machined from solid bronze - one that never fails.

I think your post is actually a response to my earlier post that mysteriously disappeared. Here it is again:

Concept 2 decided to put a slot in the swivel bushing because the part was prone to failure, and the slot made it easy to replace. Before making that decision C2 would have looked at possible solutions to the known breakage problem. One solution wold have been to machine the part from solid bronze. That would have fixed the problem for good. But C2 decided it was more cost effective to just add a slot to the existing sintered bronze design (probably a simple modification to the manufacturing die accomplished this) and charge user's a buck for a replacement when one breaks.

[Carl Watts]

The bottom line is the Concept 2 one is much cheaper to make.

Sure it may only be a $1 but the freight to get it to you is probably $8.

Its common to see this part totally missing on Gym rowers.

I could probably list mine on E-Bay and sell them internationally but nobody is going to pay for it and like I said before Joe Average doesn't even own a screwdriver. When I made these I totally overestimated the average persons ability to recognise a better part and be able to fit it.

[Ombrax]

Joe Average doesn't even own a screwdriver.

I own a screwdriver and as a cyclist I've been dealing with chains for decades, nevertheless I appreciated the fact that the new design had the slot and I didn't have to mess with the chain at all.

[Willy.VdW]

The bottom line is the Concept 2 one is much cheaper to make.

Its common to see this part totally missing on Gym rowers.

No doubt cost is an important factor.
The bushing you made certainly looks more durable, but as I don't know the lubricating proporties
of both the original and yours, I can't tell if it is more functional.
I think the C2 rower is a good product overall, but of course it isn't indestructable.
The bottom part in your photo shows that the machine suffered from severe lack of maintenance.
I don't feel the manufacturer is to blame. If this is a common thing in gyms, it means they don't
believe in maintenance as an important issue. This may not only involve the equipment, imagine
what can happen when the worn out item breaks as a user forcefully pushes at the drive...

[Carl Watts]

Its not self lubricating, you put a tiny bit of chain lube on it when doing the chain.

Common practice is always put a hard material against a soft material for a bearing surface or else they eat one another.

Mine has done 10 years and 20 million meters, its will never need replacing. Its the same material you would find in some conrod big ends.

[Willy.VdW]

Its not self lubricating, you put a tiny bit of chain lube on it when doing the chain.

I am not sure if you mean the C2 bushing or yours (or both) but I do it.
But since (many?) gyms apparently don't look after their equipment,
chances are they wouldn't lubricate the bushing either.