what's your opinion on those chain tubes that are pretty common? (HP Velotechnik, Actionbent, Challenge) what are their pros/cons if any? Are they easy to buy and install on any bent, or just certain brands?

I use them on both return and drive chain on my cheapie homemade trike. In terms of simplicity, you can't get better. It means you have one less roller to worry about, and since your return chain runs very close to the drive chain, a bit more ground clearance. Disadvantages could be a tiny bit of noise but that is partially muffled by the tube. They are easy to buy, usually normal pvc tubing 10mm cost around a dollar per metre. You would need a chain breaker, and to straighten the tube, you hook it to a wall, clamp the bottom, and pore boiling water into the tube and leave to rest. The tube then settles straight, as the hot water reshapes it (as they usually come round).
The last advantage is cleanliness for the chain and you. It cleans off the guck that can build up on your chain. It also allows you to handle your trike or bike without getting chain marks on your skin or on your clothes. This is often very important, as in recumbents, the chain travels between your legs as it comes of the front. This means that without tubes the chain can bounce around and leave oil marks on your skin.

wouldn't you have to coat the inside with some type of lube or something? Do you lose any drivetrain efficiency?

I dont like the idea. Sooo much drivetrain friction. I'd rather the extra roller. At least I'd be going a little bit faster with a little less effort. Plus, dirty chains and legs, that dont matter to me. I'd still lube my chain every 2nd ride anyway, even with a tube. My opinion is that recumbent manufactures use these as a cost saving measure, plus, in reality, they do the job they're intended to, just not as well as a 2nd roller. Chain Tubes are ****!

what if the inside were some magical material like teflon or something? would THAT reduce friction enough to be as frictionless as the rollers?

Well, if we're talking teflon as a liner, then I could see it being bascially frictionless. But then again, teflon is a very, very pricey material, which defeats the purpose of a tube as a cheap alternative to a roller setup.

I have added tubing to my trike to keep the grease and the chain where I want it. First I used drip irrigation tubing which works just fine however, when I had access to the real stuff, I installed it. The trike runs the same, but the teflon tubing is much quieter. My trike uses one roller and the tubing by the way. This is not a slow trike nor would it be any faster without the tubes. The tubing that manufacturers use is often referred to as teflon tubing and is very slick stuff whatever is in it. The Hostel Shoppe lists some for sale. The tubing I use on my trike (Logo) is a set I adapted from an ICE trike--they install them on all their trikes.

Chip
recumbenttrikestore.com

i wasn't looking for tubes as a cheap alternative to rollers, i was looking at them as superior chain protection. (and by the way, those companies i mentioned use teflon tubes.)

Superior chain protection from what? Straight path DFs use no pulleys or tubes. Chain tubes manage the chain path--that's it.

Chip

well according to HP Velotechnik's and other companies, the tubes are to keep the chain clean as well.

As a tube proponent, I can say that I don't think they matter for that. ICE claims that the tubes keep you and the trike clean. I started with tubes for that reason before I read their criteria and it is the only one that seems to matter. One thing that may be of interest is that chains seem to stay cleaner on a trike than a DF because there is no leading front wheel to send dirt all over the chain.

Chip

I've seen photos of some 'bents that have the ENTIRE DRIVETRAIN encased! In addition to chain control, the enclosure keeps ALL gunk off the chain - once lubed the post said that the chain didn't need service but once per year!

I mainly keep chain tubes on my trike, to keep all the gunk off my legs. I commute to work and I don't fancy the idea of arriving with a grey streak down my leg every day.

Some bikes need the tubes to keep the chain from rubbing on solid parts--not all bikes have clear chainlines.

I bought a first bent (a SWB) that had a lot of tubing, it was bad for two reasons--it had DRAG on the chain that you could feel. And secondly, it made cleaning the chain well just about impossible, because the tubes were always full of gunk.
This is a page showing how I cut mine down:
https://www.norcom2000.com/users/dcim...ster_tube.html
on this bike, the tension-side was clear, but the return side was not--so all the tubing could not be eliminated.

Also we note: in the US, hardware stores sell plastic piping that is pretty much identical to the tubing that comes with bikes--except that the hardware store PTFE pipe is often a different color--usually milky-white. It is the same size and texture however, and is pretty cheap to buy per-foot. It is often curled a bit because it is shipped on rolls, but it does relax and straighten out if you heat it up a bit with a heat gun.
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Cons: chain tubes are noisy, messy, and hard to clean
Pros: they keep the bike cleaner, and possibly your legs as well (depending on the bike)

My Seiran came with a choice of with/without chain tubes. The tester had tubes, and I found them annoying. I ordered mine without -- much quieter!

Careful: if you go without tubes, make sure nothing touches your chain. In this picture (https://bikezen.org/pix/seiran/target2.html) you can see a cable getting too close to the idler. You also see my equipment bag rather close to the chain. (Both problems were remedied...) Chains and idlers are very unforgiving to cables and such.

Doesnt sound like a very well designed 'bent to me .

I just got rid of one of my chain tubes tonight. It sounds great! when fall comes around and I start having to wear pants again(instead of shorts) I may have to re install it to keep my pants clean. But for now it's awesome.

I've been toying with the idea of cutting my tubes into short sections, attaching them as guides only at key points. This might reduce any friction/noise they produce. Although I've not had a real problem with them so far, I'm thinking I might try it to see if I get any better performance.

You may increase both friction (negligible in any case I think) and noise by introducing additional tube ends through which the chain must pass.

Chip

Lots of hardware stores sell PTFE tubing, and essentially it is Teflon, not just coated on the inside, but all the way through. There's a few different sub-types but they are overall very similar. The type that I mostly see in hardware stores is milky-white, where bike shops seem to use the black colored stuff. The two kinds feel identical, held in your hands. And the hardware store white stuff is even often in the same diameter/thickness that is used for chain tubes.

Below from https://www.zeusinc.com/teflon_tubing.asp
...the main problems I have seen with chain tubes is where the chain enters and exits the tubing ends. Often the chainline does not line up with the tube perfectly and so the chain is rubbing on the end-edge of the tube. This causes a significant amount of drag especially where the chain is entering the tube.

I can see where one might want a bit of tubing on a commuter/general short-run utility bicycle, but for a recreational machine I prefer to do without if at all possible. They don't keep the chain from getting dirty, and don't make the whole thing any easier to clean either.
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I'd guess the tubing is pretty close to frictionless when it's brand-new and clean, but the problem is that it doesn't stay clean for long. And it's probably acceptable on the lower-run of chain that is not under much tension and the tube ends are lined up well with the chain. It's when it's used on the upper-run that it eats into the efficiency.
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Well said Doug

I have very short pieces of chain tube on my trike, and that is just to protect the frame.

Joel.. What idler is that you've got? Does it have a "pulley" for both sides of the chain, like it looks in the photo? I'd like to get something like that to replace the POC (piece of crap) I have now that only hits one side of the chain. The other side simply sits under the sprocket.

-Tim

The idlers are made by TerraCycle, and there is two idlers a power side and a return side. It isn't cheap but does a great job. https://www.teracycle.com

I too keep my chaintubes on my trike as chainguards. They protect my pants and the paint job. You do need to pay attention to the power side of the chain. It needs a perfectly straight line for all 3 chainrings. That means you only want to hold the tube near the idler. If you use the tube as a guide on the power side, you will wear it out pre-maturely. On the return side you can guide the chain wherever you want with minimal drag. I found one article that recommends dry chain lube (teflon) for tube'd chains to keep them clean inside. Also remember not to overtighten the zip-ties as this may cause the chain to be chocked off and cause problems.