A few DIY parts for V2 Hobie Mirage drive

Sounds like chain slap to me. I think the water and hollow kayak tend to amplify the sound. If you've ridden a bike or motorcycle before, you notice that if the chain has too much slack, it will slap or pop as pressure is applied and the chain goes from slack to taught. Being that the chain is so short, there will be a very small margin of adjustment between getting slap and too tight. Keep testing the adjustment. I'm sure you'll find the sweet spot eventually.
Good luck, Kevin.

OK, I think I've diagnosed the issue, but I'm still stumped as to how to fix it.

The links below discuss similar noises from V2/GT mirage drives, and others have figured out that it is a chain issue. What seems to happen is that there is some slack in the chain on the non-power side, and that can cause the chain to catch on the sprocket, then pop back into place, and thus the noise. In the picture below, you can see some slack in the upper chain.

Of course, I can tighten the nuts to take more slack out of the chain, but there is some twist and such, so that there will be some play under full pedaling load, unless the chain is extremely tight--too tight for my liking.

So, why doesn't this happen with the Hobie cable/chain? It's a bit difficult to explain, but fairly obvious once I figured it out. Here is an attempt to explain: Unless it's extremely loose, the Hobie cable holds the chain steady, front-to-back. In contrast, my twisted chain approach allows the chain to easily move front-to-back if there is even the most minimal slack in the assembly. When moving thru the water, the water pressure pushes the chain towards the back, which is a minor issue with Hobie cable (just tighten it a bit if there is any popping noise, and it'll go away), but becomes a problem with my floppy chain approach.

The only way I can see to prevent it would be to have a cogs that are much "taller" so that the chain cannot semi-disengage when there is a bit of slack. But, if anybody has other ideas, let me know!






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https://www.stripersonline.com/surftalk/topic/649715-help-mirage-drive-v2-making-knocking-noise/#comments

https://www.hobie.com/forums/viewtopic.php?f=75&t=45246

https://www.hobie.com/forums/viewtopic.php?f=11&t=13155

My thought here is to compare the chain and cogs to a chain on the bike and the teeth on a chain wheel. The bike chain wheel has narrower teeth and probably deeper teeth that have more "room" fitting into the chain links and of course, a tensioner to insure proper constant tension. Getting your two chain system spot on as far as alignment goes is a problem. One remedy might be to use clip in pedals which allows for a back pull on the drive arms on the return stroke and thus keeps constant tension on the chain.

One other thing to consider. From the photo it appears that the chain is a cheap non O or X-ring chain. It wont be a cheap solution but if you swapped the existing chain for a O -ring style, it may quiet things down some. The O or X ring chains tend to be a little stiffer due to the friction of the rings. That may be just enough to eliminate the sloppiness of the non O-ring stock chain. Any motorcycle shop should have descent chains in stock like DID or RK brands. An added benefit is that the O-ring keeps water out of the pins so the chain will last longer.
Kevin.

One other thing to consider. From the photo it appears that the chain is a cheap non O or X-ring chain. It wont be a cheap solution but if you swapped the existing chain for a O -ring style, it may quiet things down some. The O or X ring chains tend to be a little stiffer due to the friction of the rings. That may be just enough to eliminate the sloppiness of the non O-ring stock chain. Any motorcycle shop should have descent chains in stock like DID or RK brands. An added benefit is that the O-ring keeps water out of the pins so the chain will last longer.
Kevin.

I didn't even realize that there was another kind of roller chain. The chain that I used is an exact match to the chain that Hobie mirage drives use (#35 stainless). I do see some #35 O-ring type, but not in stainless. Besides, I doubt that would solve the issue, as it seems to me that it's an inherent problem with having flex in the "wrong" direction.

My thought here is to compare the chain and cogs to a chain on the bike and the teeth on a chain wheel. The bike chain wheel has narrower teeth and probably deeper teeth that have more "room" fitting into the chain links and of course, a tensioner to insure proper constant tension. Getting your two chain system spot on as far as alignment goes is a problem. One remedy might be to use clip in pedals which allows for a back pull on the drive arms on the return stroke and thus keeps constant tension on the chain.

Out of desperation, I tried filing the teeth on the Hobie spindle to be narrower, like on a bicycle. Sadly, that didn't help. If I could make them stick out a bit further, that might do the trick, but that does not seem easy.

Not an exact analogy, but imagine a bike chain that has a similar twist to it (of course, you could actually pedal it, but bear with me...). Then, you would not be able to shift, as the derailleur would be pushing on the top/bottom of the chain, instead of on the side of the chain. If you could get the chain super-tight, then you might be able to shift, but it would be very sloppy. Anyways, as I see it, something comparable is the problem.

Clipless/clip-in pedals is an interesting idea, though...

You already have 9/16ths bike threads on your drive arms so popping in a pair of clipless/clip in pedals is easy. Got any bike shoes with cleats running around? I've used mtb sandals with cleats for years. Work good on the water with neoprene socks. For long distance pedaling clip in pedals really make a difference in spreading the muscle work load through out the leg muscles.

A quick update...

I noticed that my "twisted chain" had one extra link on the part that goes over the chainring (as compared to the standard Hobie chain/cable), so I removed that. It is now possible to adjust it to eliminate the popping noise, although it still needs to be a little tighter than I'd prefer. Due to the shorter overall length, I've got to get longer eye bolts to test it more thoroughly--I've ordered them and will update once I've done the additional testing.

In addition, I have figured out exactly where the problem arises. When pedaling with force, all of the slack in the system accumulates in the front chain, on the side with the "up" fin in front (same side as the pedal that you are pushing on). It is fairly easy to mimic this: If you put the mirage drive flat on the floor with the fins out to the side, and put pressure on the pedal that's to the rear, you'll see where the slack in the chain appears.

The upshot is that the rear chain is never a problem, so it looks like it'll always be possible to use my indestructible no-cable chain to replace the rear-side Hobie cable-chain. So, even in the worst case, I'll only need to buy 1/2 as many expensive chains from Hobie.

Anyways, I should get a chance sometime next week to test it enough to give the final word on this mod...

Nice work!  I wonder if there is a way to attach a spring or other device to provide tension during that moment of slack?  Might lessen or eliminate the noise. 

Lots of fishing lures make rattle or clunking noises - maybe that noise could be a desired feature?  Seriously though, great work on building this!

Seems to be working perfectly with the V2 drive. I still need to do a bit more testing with the GT drive before I can declare victory...

https://youtube.com/shorts/sKxXDdPPQHk

Seems to be working perfectly with the V2 drive. I still need to do a bit more testing with the GT drive before I can declare victory...

https://youtube.com/shorts/sKxXDdPPQHk

Awesome! Very cool!

that sweet (no-)sound of victory! 

Trying to make a replacement turbo fin
(in case you cannot see the url, try youtu.be/UoMFN7zjP1s)

site doesn't recognize youtu.be links, but clicking the link will convert it back to youtube.com and that link will work in your posts.

site doesn't recognize youtu.be links, but clicking the link will convert it back to youtube.com and that link will work in your posts.

I see. Is there any chance of increasing the size of images that will be accepted. Photos on my iPhone seem to default to 6M, and I believe they won’t post unless they are smaller. Kind of annoying to have to resize…