Straightening Chainline Recumbent 6' Chain Front Hub Motor

[Recumbent Bicycle Source]

1. My recumbent has a long... very long chain. When I measure distance from where the chain leaves the back derailleur to the furthermost point of the large chain ring the distance is 72". That's a whole lot of chain (just over 12' of chain total!) Proper "chain line" on this bike is really not possible... but better chain line?

2. I've attached a photo (See Below) that will help make it easier to understand what I want to accomplish.

3. I want to "clean up" or "straighten" the chain line by moving the front chain rings out away from the boom. Options? Is this even possible (Mfg Specifications/Standards prevent this?) 68mm bottom bracket with a longer spindle... spacers? Or?

4. I also have other Electric diamond frame bikes so just saying get a different bike will fall on deaf ears. I've already got 3K riding on the Hub Motor, but the bike would be more enjoyable with a better chain line.

So again if you look at the picture it represents how my current chain line looks from above now. If I can move the front chain rings out the chain line will straighten out. Ignoring for now the other chain rings because I don't use them. For now the inner chain rings front and back are just acting as spacers. I could easily go single speed and ride just fine. The problem then becomes a chain which is too close to the frame and interferes with the front fork needed for the hub motor. If I take the front hub motor off and swap back to the original fork most of this takes care of itself. But I don't want to do that.

I don't really care about "Q Factor"... and I know it's not directly related to spindle length and chain ring placement as these are standardized for the most part (Road chain line at 43.5mm, Mountain at 47.5 or thereabouts). And extra inch added to the Q-factor isn't going to effect the way I ride on this bike because I am not straining my knees in a reclined position and the motor is doing all of the real work... I'm basically just resting my feet and spinning.

So if I am making any sense at all...

How can I move the front outside chain rings out more so I can have a straighter chain line over all. Moving the front chain out even half an inch would solve the problem. And I'd just ride all the time in that position. Noting again...I have a 68mm bottom bracket. Is this even possible as all manufacturers are making cranks to a standard by application. Very confusing finding a crankset to do this... easy in concept. I'm fine replacing the entire front crank, bottom bracket, etc.

Advice?

 

[Recumbent Bicycle Source]

After too much reading... here is what I'm thinking (Probably Flawed)

Buy a Shimano FC-M590 Triple Crank with a 50mm Chainline. This should give me 2.5mm out to the right.

Then install 2 5mm spacers between the first and middle, and middle outside ring. Should give me another 10mm

The two combined will give me .4921" which is essentially the half inch I need to clear the fork.

I would only be able to use the outside 42T ring... which is what I want, because the chain would now drop between the rings if I tried to shift. Oh well.

Now... can you install spacers between the chain rings on the FC-M590?

 

[amberwolf]

I'm a little uncertain about exactly what you want, but if it's like in your drawing above, where you are using the chain on the two smallest rings, you would be much better off to ride using the largest front chainring, and then whichever rear sprocket gives you the same ratio.

You'll get a straighter chainline, and you'll have more teeth engaging the chain on both ends of the chainline, meaning you'll wear the sprockets less and less chance of chain skip, jump, etc.


As for the long chainline, you could probably add a guide along the return (bottom) chain path because it's the slackest part of the system, and the most likely to bounce around and cause derailings. On my CrazyBike2, I use an old rear derailer mounted on the bottom of the frame, locked in position to ensure the chain lines up with the bottom of my single-speed sprocket on the rear wheel, becuase of bounce.

The same thing can be done on the top of the chainline, too, if your problem is that it won't stay on the front ring instead of the rear.


Regarding singlespeed; if you need to use a single sprocket freewheel to help the chainline, but it doesn't stick out far enough, then you can either simply rearrange the sprockets on your multispeed freewheel to put the sprcoekt you want in the middle isntead of one end or the other, or you can use spacers on the threaded part of the hub to bring out the single sprocket freewheel out further from the hub, and if there aren't enough threads to secure the freewheel then use an old BB cup threaded in there and jammed against the hub's threaded area.

 

[Chalo]

The longer the chain run, the less chainline matters-- because it's about the chain angle, not the gross amount of lateral misalignment. With 6 feet between centers, your chain will tolerate a great deal of misalignment without symptoms. However, if your chain passes under an idler, then it's the chainline between idler and sprockets that counts, not the relative alignment of the sprockets. So the lateral location of the idler and the distances between it and the sprockets become more critical, those distances being shorter and exaggerating the effect of misalignment on the chain's angle.

If you're only going to use a single chainring, then only have a single chainring on the crank, and change its position (inner or outer) and/or the length of the bottom bracket to get the chainline you want.

 

[Recumbent Bicycle Source]

The picture is not what I'm trying to do... just an example of a chain line.

I want to run it on the Large Ring (furthest out) and the 2nd smallest ring.

This pushes the entire chain ring OUT.

The reason is to stop interference of the Chain hitting the side of the Fork (This is an issue only with Recumbent High Racers). Right now I have to use a chain tube and the tube rests against the fork.... thus the chain is rubbing on the side on the inside of the chain tube and the chain alignment is terrible. Shifting is so very sloppy... so running on the large chain ring (Which I will reduce to a 42T) and the 2nd smallest ring (to avoid jamming) should solve these issues. Gearing absolutely doesn't matter with the hub motor. I don't need to shift at all.

The only reason for a Triple is to move the chain out. A single would actually be preferred but it would be centered and move the chain in.

The is really hard to explain.

 

[amberwolf]

If gearing does not matter because of the hubmotor, do you actually need/want to provide any motive power via the pedals? Or are you only wanting to get some exercise by pedalling?

If the latter, then you could actually remove the chain, and simply tighten the bearing cups to cause sufficient friction to push against as hard as you prefer. This would need readjustment from time to time, and eventaully require replacement of those, but it would let you exercise without cranks spinning wildly/freely, and remove the entire problem of the chainline. And it is extremely simple to do, as long as your cranks do not have cartridge bearings. If they have cartridge bearings, it would require some other method to generate this friction, or changing to the older type of bearing/cranks.


If you do actually need to keep the chain, then there may be a few ways to alter the chainline, but I'd need to see exactly what you have to be sure of a solution.


It might be easier to explain to us if you would post pictures of your actual setup. I don't remember seeing any pics of your bike in any of your posts. The way you described the drawing, I mistakenly took it for how your chain was actually setup.


I know generally what various types of recumbents look like, and variations of each basic type, but without seeing your actual setup, and seeing the exact problem(s), it's hard to know exactly what to recommend to fix them.



I know you said you arent' much for DIY, but if I understand your problem correctly, it sounds like you may need to do some of that to solve it.

With pictures of your bike and problem, someone here could probably help you figure out exactly what to do and how to do it, and with what parts--or at least get you a lot closer than the vague suggestions we can offer at present.

 

[Chalo]

Try using the outer chainring position and a long bottom bracket spindle, like 127.5mm from Shimano or 135mm from Sickbikeparts.

A crank set up to have three rings can just as easily have one ring in any of the three positions.

You could also try using a real bicycle, since all these design issues were worked out generations ago. But if it pleases you to discover firsthand why a normal bike is normal, then by all means try doing things the hard way first and figuring it out for yourself.