Transfer Chain
NOTE: This is written for the Dyname 4, but the Dyname 3 is extremely similar regarding the transfer chain.
Sprockets primarily wear due to chain elongation, which is turn happens as the chain's pin/link interface wears. As a worn chain mates with the sprocket, the extra length between links causes the chain to ride up on the tooth, and most of the power is transferred through that one tooth until the next tooth engages. This wear a divot into the face of the sprocket's tooth.
The Dyname 3/4 motor sprocket is particularly interesting because it uses o-rings on either side of the sprocket which the chain actually rides on. The chain rollers only engages the face of the sprocket tooth, so as the chain wears it doesn't have the opportunity to ride up on the tooth. The chain wears a groove into the o-rings, so the o-rings lose their effectiveness before it's readily apparent that they're worn.
NOTE: The maintenance intervals mentioned below are very aggressive because doing the maintenance is fast, cheap, and easy, while the costs of sprocket wear are very high. Therefore we always want to do the maintenance before the maintenance is actually needed and parts can begin to wear.
To keep the sprockets from wearing, we want to:
- Regularly replace the transfer chain.
- Regularly lubricate the transfer chain.- Regularly replace the motor sprocket o-rings.
Replace the transfer chain
I don't want to wait until the transfer chain has notable wear before replacing it in order to minimize sprocket wear. Therefore I plan to replace the chain on a fixed interval. The original Tsubaki chain went 450 miles 0.25% elongation, so I think replacing it at 200 mile intervals is extremely safe. Since new chain usually comes in 10 foot sections, it should last 1,800 miles. For me that works out to approximately $10 per 200 mile replacement.
Tsubaki is a quality Japanese manufacturer, and their prices reflect that, However, they are available on the surplus market at a reasonable price. Timken also makes high quality #25 chains under the Diamond name (www.diamonddrives.com). ANSI #25 roller chain is readily available from other manufacturers and through Amazon and McMaster-Carr (and many other online sellers), though the quality and change interval on those is unknown.
The stock Dyname 4 chain is only 26 links long (including the connecting link), so a single replacement chain should last through several replacement intervals. Be sure to use a new connecting link when replacing the chain.
NOTE: Unfortunately, it does not appear anyone makes an o-ring or x-ring #25 chain, which would be ideal. If anyone finds one, please comment here to let me know.
Lubricate the transfer chain
Depending on what documentation you're looking at, Rocky Mountain says to use standard chain lube or Park Polylube 1000. Both of these recommendations are wrong:
- The chain is enclosed, so there's no reason to use dry lube or dirt shedding wet lube, and the lubricant can be optimized to reduce wear/elongation.- Grease cannot get inside the rollers and plates, so it won't lubricate where the chain actually needs to be lubricated to prevent wear/elongation.
Tsubaki, the chain's manufacturer, recommends using an SAE 20 oil to lubricate the chain (pages 10-11: https://catalog.ustsubaki.com/view/303394094/10/). Since the chain will be turning at a decent RPM we also want something which is very tacky so it'll stay in place and won't fling off. In my opinion the best option is Mobil Vacuoline 1409 which is a way lubricant designed to minimize wear on very expensive machine tools (a "way" is where the moving parts of a machine tool slide on each other). It's in the same viscosity range as SAE 20, but includes a lot of tackifiers to keep the oil in place and prevent it from being flung off.
A temptation would be using chainsaw bar oil since it's also loaded with tackifiers, but all the ones I've looked at were heavier viscosity than the Tsubaki recommendation.
Tsubaki recommends oiling the chain every 8 hours of use. Lubing the transfer chain is easy, as you only need to remove the 4 bolts holding the left hand motor cover in place. Just brush the oil into the rollers of the chain.
Immersion hot waxing might also be a reasonable alternative, but a bushing chain like the #25 transfer chain is very hard to wax due to the tight tolerances preventing wax getting to the pin. However, Silca does recommend their Synerg-E oil-based lubricant for this application. I haven't tried I myself, but it seems reasonable.
NOTE: Using oil instead of grease on the transfer chain will increase the chain noise slightly.
Replace the motor sprocket o-rings
The stock o-rings appear to be nitrile/Buna-N, size -208, and a 75A-80A durometer, which is problematic because nitrile doesn't come standard in that durometer (nitrile is available in 70A and 90A).
My solution was using square profile 208 o-rings in a 70A durometer. Because more of the o-ring supports the chain it provides the same chain tension as the stock o-ring as measured by mm slack in the middle of the chain: 8mm for square profile 70A vs. 8.5mm for the stock. This amount of slack is also well below Tsubaki's maximum tension (page 15: https://catalog.ustsubaki.com/view/303394094/14/). The square profile will also better support the chain and reduce the chain eating into the o-rings.
Square profile -208 70A o-rings can be easily be found at any o-ring supplier or at McMaster-Carr: https://www.mcmaster.com/4061T23/
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| Square profile o-rings installed. |
Since I'll be oiling the chain every 8 hours, I'll inspect and potentially replace the o-rings at the same time.
