PDA

View Full Version : Chain line management on my modified Voyager



bambuko
02-11-2013, 01:24 PM
Like most of you I have taken Brad's plan and tinkered with it to get "my" bike :rockstar:
However I now got to the stage where I need to sort out the idlers for chain management and because my Voyager is so different to the original I am a bit stuck :confused:

Here is what it looks like:

In lowest gear

https://lh6.googleusercontent.com/-K4Oh2DVe0t4/URkz6DPAgaI/AAAAAAAANKQ/XmC9yaNw4Tk/s800/IMG_6654.jpg

Clearly no problem, might just need to do something to miss handlebars

https://lh3.googleusercontent.com/-t8XBmtE1Qnk/URkz65DWuVI/AAAAAAAANKQ/1E8lOuiFp_Q/s800/IMG_6651.jpg

But... in the highest gear

https://lh4.googleusercontent.com/-MJYkMi6BLCE/URkz7TjdHBI/AAAAAAAANKQ/sCZVAVxZ8wA/s800/IMG_6659.jpg

It rubs the seat bottom and is (too) close to the suspension pivot point - I can see it will rub when suspension works.

https://lh3.googleusercontent.com/---3zgowd0-Y/URk0AjEj4UI/AAAAAAAANKQ/1kwJnKaGeAs/s800/IMG_6662.jpg

Another view

https://lh6.googleusercontent.com/-5_m8-cPcBWk/URk0A5lV6YI/AAAAAAAANKQ/KI8rOdo54do/s800/IMG_6664.jpg

How would you guys handle this chain?

Radical Brad
02-11-2013, 02:08 PM
A 3-4" idler just ahead of the seat for the drive chain. Then use the hose method for the return chain.
The idler will push the chain just under the pivot and stop it from smacking the seat base when you burst into a hard pedal stroke.

Brad

bambuko
02-11-2013, 02:56 PM
Thanks Brad!

That's just perfect :rockstar::

https://lh3.googleusercontent.com/-NYfx_f1wbeU/URlMQfZAWUI/AAAAAAAANKw/rLg0euIef7c/s800/chain%2520line.jpg

trikedoc
02-11-2013, 06:41 PM
Thanks Brad!

That's just perfect :rockstar::

https://lh3.googleusercontent.com/-NYfx_f1wbeU/URlMQfZAWUI/AAAAAAAANKw/rLg0euIef7c/s800/chain%2520line.jpg

Couldn't you use a pulley between the seat back and rear suspension pivot point to slightly depress the top chain

Radical Brad
02-11-2013, 07:58 PM
Couldn't you use a pulley between the seat back and rear suspension pivot point to slightly depress the top chain

That would also work, but there may then be an issue at the handlebar area.

Brad

Ticktock
02-11-2013, 09:48 PM
My first question would be "Where did the chain run on the original bike? " I can see a suspension induced bounce problem coming in here without some thought.
Can you give a pic showing the swing arm from the top, chain side, showing how much room there is between the whel and the swing arm over the top of the swing arm (where I think the original cahin was)
And while a single pully to hold the chain down just behind the seat would work while in low gear and a tight chain and no bumps, put in top gear, slack chain and a bump and it would almost certainly not stay on the pulley. Easy to over come with another pulley, but does not address the possible SIB problem .
Steve G

bambuko
02-12-2013, 06:29 AM
...Where did the chain run on the original bike?...

Similar to "my" Voyager - (not very good, but hopefully clear enough) picture:

https://lh5.googleusercontent.com/-Tr8qF4pQ69w/SuLygZxZFaI/AAAAAAAAIWY/1CIWzp03RQY/s800/001apollo-abyss_donor.jpg


...how much room there is between the whel and the swing arm over the top of the swing arm (where I think the original chain was)...

No, the original chain run below swing arm - see the pic above and close up below:

https://lh3.googleusercontent.com/-Nt_WYXehpes/SuLyhAuQkkI/AAAAAAAAIWc/EQf_1-xDNOw/s800/002apollo-abyss_donor1.jpg


...I can see a suspension induced bounce problem coming in here without some thought...
Well... that's why I am hoping that discussion here will help me to avoid disappointments.
It's not for nothing that TexasTuff called his Voyager (Pogo) (http://texasrecumbents.wordpress.com/our-recumbents/voyageur-lwb/)



...And while a single pulley to hold the chain down just behind the seat would work while in low gear and a tight chain and no bumps, put in top gear, slack chain and a bump and it would almost certainly not stay on the pulley...

I am slightly confused about your low/high gear...
As far as I understand it in low (front 32/ rear 23) there is plenty of slack in the chain and in high (front 52/ rear 11) the chain is tight - see picturebelow. Having said so, I do agree with you that the issue is chain staying on the pulley.

https://lh5.googleusercontent.com/-CkTEqy36u2o/URoliMgG3uI/AAAAAAAANLI/9USW056_p4w/s800/high-low.jpg

I like Brad's suggestion and (subject to clearing handlebars) it can be made to work with the idler behind or in front of the seat. It is simple and least of the necessary evil (any pulleys/idlers in the drive chain are to be avoided if possible) but I am concerned about pogo effect:confused:

I guess it will be down to experimenting... unless somebody knows the answer?

Ticktock
02-12-2013, 08:44 AM
Why it does not make sense is because your bike is not in top gear! Top is 52/11, not 52/34! the rear of the chain is lower, and less likely to stay on the pulley.
52/11 is a good top gear , by the way.
The chain looks unusually slack when not on big cogs.. I use the same gears at back, with a 52/40 at the front, so I can't duplicate your situation, but it does seem that the derailer is not pulling tight enough when on the smaller gears. On 52/34 my chain is tight, with a bit to spare. On 40/11 it is not as slack as yours!! That does not help solve the other problem though.
It really is a problem as to which way to go, as I really see Suspension bounce as a problem. I have seen these style here in Beijing, and wondered what happens if ridden hard.
Ideally the chain should pass just above the suspension pivot point, but because of the wide swing arm, this is going to be difficlt/.
Looks like the best you can do is to get as close to the pivot point as you can.
Just had a look at the Voyager plan, and another look at your bike, had a beer, then another beer, and came to a decision as to what I would do if It was my bike. I hope it helps you, and that it works if you try it.
Basically, follow the plans, as close as you can. Use a rear idler just as Brad has, but you can only get as high as you can get, allowing for suspension travel and chain clearance . Check this idler position with the chain on the 34 cog then the 11, and at both extremes of suspension ,movement, Ignore the front when you do this. Once that pulley is fixed, its time to fix the front, pretty much as Brad has done .
Make sure that you have room for handle bars to miss the chain and the pulley on full left and right steering.
The return chain goes any where you like in a hose guide, as per the plans.
I wish I could say that this will eliminate bounce, but I think its as good as you are going to get, and if I was a gambler, I'd bet you will be OK.
Hopefully, when you get the puleiys and guides srted out, the tension will look better. Your chain is about 12 inches longer than mine.
When you make up the final chain , get it as tight as the derailer will allow when on both big cogs, and full suspension travel--it's not the official way to set it up, but with the big steps on the front cog, its about the only way wou will get any tension when you use the smaller cogs. Remember that you will (or should) never be using both small cogs together! Its a good way to wear out an 11 tooth sprocket!
Steve G,
Beijing.
By the way, where did you get the front chain rings--I've been told here that I can;t get a 52 with triple cogs! Would love to get a set like yours!

bambuko
02-12-2013, 11:50 AM
Thanks Ticktock,

I guess this is what we are talking about?
Bottom half shows swing arm deflected by about 10 deg (I guess this is max ?)

https://lh5.googleusercontent.com/-sUG9ZjHdsbI/URpvfmRoZ-I/AAAAAAAANMU/6m4qf20ZZCE/s800/Drawing1%2520Layout1%2520%25281%2529.jpg

BTW 52 with triple cogs - you caught me talking out of my a**e :rolleyes4: - it is standard 22/32/42
Yes I would also want one with 52, but for now I am using bog standard one.
As for the source, here is one (Vuelta):
http://www.gaerlan.com/bikeparts/parts/crank/crank.html

TexasTuff
02-12-2013, 12:41 PM
Hi bambuko
The drawing that Brad did should help a lot unless you want to make it a double pulley to hold the return chain up out of the dirt.
I would build a truss under the seat all the way back to the hinge. Under the seat is where I bent the main boom. You have very good photos to see what I am talking about. Picture riding this bike off a curb. The shock bottoms out and that puts a lot of upward pressure on the seat upright and with a lot of leverage being transferred down to the main boom. Right in front of the seat upright and under the seat is where my boom bent. A simple truss under the seat should strengthen this. This may not be a problem for you if you are not up to my 190 lbs or my sons 210 and you don't ride off curbs.
Pogo did bounce a bit. It may have been that the spring was weak on the shock. If I were to do it over again I might mount 2 shocks on it so it did not have such a soft ride. Maybe even a small motorcycle shock with a coil over instead.
I'm not an engineer, I just know what my eyes tell me. If you grab the seat upright and pull forward and put your foot on the seat and push down you will probably see some flex in the boom. Some flex is good, but a lot of flex does not always return to its original shape.
Best of luck with it. Their fun to ride.

bambuko
02-12-2013, 01:02 PM
Thanks TexasTuff,
I am indeed around 210lbs, but I have modified the main boom (mine is 2" diameter) so I am hoping to get away without a truss?

I would also prefer to keep things as simple as possible, hence my preference for a single idler as per first drawing. The question is - how much of your pogo was caused by the spring you had and how much by chain line bounce?
BTW - how heavy was your Voyager?

Brad quotes his around 40lbs, mine so far is about 39lbs and there are still few bits to go on ...

trikedoc
02-12-2013, 01:18 PM
bambuko, I think you will find there will be a lot more than 10 degrees of suspension travel.
Have you sat on the bike to see how much the suspension compress or bounced on it? Thats why I suggested the pulley be above the top chain just in front of the suspension pivot. Preventing the chain from raising up and hitting the bottom of the seat and allowing the chain to follow the motion of the swingarm. It may require a small pulley just forward and below the back pulley to prevent the chain from bouncing out of the upper pulley. this would give a near straight upper(power)chain run above your underseat steering.
When your chain is one both the front and rear largest gears is there any slack left in the rear chain tensioner?

TexasTuff
02-12-2013, 01:36 PM
I never weighed mine but it was pretty much built to specs. I think 40 lbs would be close.

This was my sons and mine first build and I think it turned out fine except for the bounce and it was mostly from components and not from chain line bounce.

If you decide you don't like under seat steering you can drill a hole all the way through the boom (just in front of the seat) and mount the head tube through the boom. That way you can have USS or OSS either. My last two bike have been built that way. I'm presently gathering parts to convert my present ride to OSS.

I like the chain stays on your bike, looks cool and keep things out of the way.

George

bambuko
02-12-2013, 01:45 PM
thanks trikedoc,

I guess you are talking about something like this:

https://lh6.googleusercontent.com/-KSYeM5J89uU/URqM1Y7SpOI/AAAAAAAANNQ/CALY0ACA_Fk/s800/chain_management.jpg

Perfect from a point of view of chain bounce and not sensitive to the amount of deflection!
The only problem is that we are now facing 3 idlers (from the original simple 1) and I am concerned about power losses in the chain drive...

trikedoc
02-12-2013, 02:07 PM
thanks trikedoc,

I guess you are talking about something like this:

https://lh6.googleusercontent.com/-KSYeM5J89uU/URqM1Y7SpOI/AAAAAAAANNQ/CALY0ACA_Fk/s800/chain_management.jpg

Perfect from a point of view of chain bounce and not sensitive to the amount of deflection!
The only problem is that we are now facing 3 idlers (from the original simple 1) and I am concerned about power losses in the chain drive...

I wouldn't use the one in front of the seat. The rear two pulleys would be almost touching. The lower one there to prevent the chain from dropping out of the bottom of the upper one. Bottom one shouldn't cause any chain deflection. As for bottom chain support Brad's bracket and tube support would provide minimal drag.

bambuko
02-12-2013, 02:35 PM
I wouldn't use the one in front of the seat...

I like this one a lot, from a point of view of chainline simplicity, clearing handlebars easily and rear idler being exactly where it should be to avoid chain induced bounce, but as you can see from the picture below, I would have to do something about seat bottom ie raise it?

This would cause another problem - bottom bracket at the moment is just in line/slightly above seat level. Any increase in the seat level would put bottom bracket too low...

Hmm :confused:

https://lh4.googleusercontent.com/-YUF8aLN-Hy8/URqXjCkpTTI/AAAAAAAANNw/dYhAaPJkZBE/s800/chain_manage.jpg

ps - I wasn't concerned about the losses on chain return, it's the chain drive that's I worry about.

trikedoc
02-12-2013, 04:23 PM
I like this one a lot, from a point of view of chainline simplicity, clearing handlebars easily and rear idler being exactly where it should be to avoid chain induced bounce, but as you can see from the picture below, I would have to do something about seat bottom ie raise it?

This would cause another problem - bottom bracket at the moment is just in line/slightly above seat level. Any increase in the seat level would put bottom bracket too low...

Hmm :confused:

https://lh4.googleusercontent.com/-YUF8aLN-Hy8/URqXjCkpTTI/AAAAAAAANNw/dYhAaPJkZBE/s800/chain_manage.jpg

ps - I wasn't concerned about the losses on chain return, it's the chain drive that's I worry about.
Your drawing still shows some upward chain deflection buy the lower rear pulley. The upper back pulley can be brought forward say half way between the suspension pivot point and the seat back riser. then lowered a little to keep the chain from contacting the seat bottom. As to the seat mounting tabs it looks like you welded them at the center of your main frame tube. Then used spacer blocks between the tab and seat.
If you weld the seat mounting tabs on flush with the top of your main frame you would gain at least 1" of additional chain clearance

bambuko
02-12-2013, 09:13 PM
Thank you guys, for all your contributions!
I have decided to remove current seat and it's brackets.
New brackets will raise seat just enough to clear the chain and allow this layout:

https://lh6.googleusercontent.com/-1DOoqyvNUBs/URrymoulekI/AAAAAAAANOQ/PZGp5-6huAQ/s800/chain_management%2520Layout1%2520%25281%2529.jpg

Idler "A" will be halfway between idler "B" and the handlebar, to both help clear handlebar and prevents chain dropping away from idler "B".
Idler "A" will only come into action when there is a slack in the drive chain, otherwise leaving clear and straight chainline between crankset and idler "B".

At least that's the theory :cheesy: - I will report the result as soon as it is completed and tested.

In the meantime the only thing that still bothers me (and I do not have an answer to) is the fact the rear dérailleur seems unable to take up chain slack at low gear, while still straining very tightly at high gear :confused:

It could be something to do with dérailleur cage? I would guess that I need long cage (longest possible) to take up all this slack and to be honest the one fitted for this test is just some old one from trashed bike so I don't even know whether the cage is long, short or medium?

Ticktock
02-12-2013, 09:18 PM
Thats pretty close to what I would do. The front pulley could (?) be placed under the rear of the seat, so it just misses the seat, and the chain just passes clear of the seat base, but over the bars, and with just enough push down to keep contact with the rear pulley on full bump.
The rear pulley is shown exactly where I thought it would fit.
Unless you have some good hills in your area, you might want to try a 52/40, as 52/11 is a really great top gear for this bike, and 40/34 should manage any mild hills with ease. 42/11 you will soon find is a bit low.
Raising the seat by an inch would make no difference in comfort or speed unless you are trying to break records. Mine is raised three inches, which is too much, so I will drop it by two inches, just to be more comfortablke when stopped. But you should not need to do this.
Steve G

trikedoc
02-12-2013, 09:31 PM
In the meantime the only thing that still bothers me (and I do not have an answer to) is the fact the rear dérailleur seems unable to take up chain slack at low gear, while still straining very tightly at high gear :confused:

Is there anyway to increase spring tension on the rear derailleur? I think its just the shear weight of all that chain. When you get all your chain management in place things will look a whole lot better.

bambuko
02-12-2013, 09:40 PM
...Unless you have some good hills in your area...
Unfortunately I got plenty of hills :mad: and I am a fat old fart in c***p condition, so I need all the help I can get :punk:


...front pulley could (?) be placed under the rear of the seat...
I intend to initially make it's position adjustable (clamped to main boom with j-clips) until I am happy that it works OK.


...Is there anyway to increase spring tension on the rear derailleur? ...When you get all your chain management in place things will look a whole better.
No there is no way to increase the tension and anyway I don't think it's the lack of tension, because like I say, in high gear dérailleur pulleys are straining almost horizontally, whilst still slacking in low gear... so it seems to me to be cage size related?
I hope you are right :rockstar: and I intend to sort out the chain management before I decide what to do about the dérailleur.

trikedoc
02-12-2013, 09:58 PM
Unfortunately I got plenty of hills :mad: and I am a fat old fart in c***p condition, so I need all the help I can get :punk:


I intend to initially make it's position adjustable (clamped to main boom with j-clips) until I am happy that it works OK.


No there is no way to increase the tension and anyway I don't think it's the lack of tension, because like I say, in high gear dérailleur pulleys are straining almost horizontally, whilst still slacking in low gear... so it seems to me to be cage size related?
I hope you are right :rockstar: and I intend to sort out the chain management before I decide what to do about the dérailleur.

I couldn't tell from your donor (photo of the wrong side) but is the whole derailleur angled forward more than on the donor? Maybe due to the whole swingarm angled down at the rear more than when it was on the donor? But really your asking the derailleur to pull the slack out of three times the original chain weight.

Ticktock
02-12-2013, 10:05 PM
There are now too many different pics of this bike as to be certain which one we are talking about!
The maib concern is to get the drive chain into a position that does three things.
Eliminate or reduce SIB,
Clear the frame and bars,
Clear the seat.
WE can't get the chain above the pivot point on the swing arm without a major rebuild of what I think is an alloy arm. So th next best thing is to get as close as we can . Its the chain position that counts, not the pivot of the idler pulley.,so in this case, placing rthe idler on the arm pivot is not the best answer we have . The chain can be pudhed up to very close to the pivot point (and I think it will work OK at that point), but it then needs to be pulled down slightly to mis the seat. With my suggestion, the chain is almost sandwiched between the two pullies as they are quite close together, and the chain is kept high enough to give room for steering, with the pulley well clear of the bars.
As to your derailer? To gather up all the chain it needs to handle 43 links . My MTB does this ok, with a bit of slack on the the two small cogs, which are never used together. My LWB needs 35 links, and it does this with heaps to spare, so there is a problem with the derailer somewhere--it does not seem to be gathering enough chain when on the small cogs. You might get two links out of that chain and still get both big cogs, but thats about all. If you can get it to work when on the 22 at front and middle cog on the back, that should be enough for normal use.
Steve G,
Beijing

bambuko
02-12-2013, 10:07 PM
I couldn't tell from your donor (photo of the wrong side) but is the whole derailleur angled forward more than on the donor? Maybe due to the whole swingarm angled down at the rear more than when it was on the donor? But really your asking the derailleur to pull the slack out of three times the original chain weight.

The swing arm is roughly the same position as on the donor, so this shouldn't change the dérailleur angle, but I can see that in the low gear on my Voyager, lower jockey is only just behind upper jockey, whereas on the original donor it would be far behind making it almost horizontal backwards.
So this would point to the lack of tension and when combined with triple chain length... it might be just the answer?
Don't know whether fresh/new dérailleur would make a difference?

bambuko
02-12-2013, 10:15 PM
...There are now too many different pics of this bike as to be certain which one we are talking about!...
We are talking about final design I have settled on as shown in post #18
What is "SIB" ?
and... yes I am beginning to think that this particular dérailleur will need to be replaced!

Ticktock
02-13-2013, 12:11 AM
OK, just make sure that the chain is going to keep on the rear pulley with suspension completely unloaded(bike up)
SIB---Suspension Induced Bounce.
There is a problem somewhere with the derailer in my oppinnion. Does not seem to gather enough slack chain.
Let me know how you like USS, as mine is high bars, and as all my riding is in city traffic, I have been reluctant to change.
I can actually fit both on my bike (at the same time), so maybe I should stop making excuses and give it a go!
All the best with the build, looking good so far.
Steve G

adrian
02-13-2013, 11:14 PM
I had some interesting chain-related adventures on a similar Voyageur build (http://www.brennans.net/adrian/bike/).

I initially went with a single idler, but the chain wouldn't stay on so I added a second as per the plans. That lifted the chain line nicely, but caused some interference (http://www.brennans.net/adrian/blog/archives/552) with the frame (diagnosis here (http://www.brennans.net/adrian/blog/archives/588) and here (http://www.brennans.net/adrian/blog/archives/642)). The picture here (http://www.brennans.net/adrian/blog/archives/653/img_0677) is after modifications, and shows the chain under no load about an inch below the suspension pivot With me on the seat and the chain under load it's a little above, and there's slight but noticeable SIB at low cadence. Notice also in that picture the rear derailleur position for middle chainwheel and largest rear sprocket. The chain is deliberately too short to fit around the large chainwheel/large sprocket - a combination I'd never use anyway.

I hope things work out for you... and if not it's not too hard to tweak these creations, is it.

Cheers,
-Adrian

bambuko
02-14-2013, 05:55 AM
Thanks Adrian, I tried to refer to your webpage when I pondered my options but for some reason it was playing up just when I needed it ... anyway, it's back now so I can benefit from your experience as well - thank you.

Our bikes are effectively identical, apart from one significant difference - the chainline management.
Yours follows standard Voyager design with rear idler "B" having chain going above it (hence your problems with chain rubbing on the swing arm). This design is meant for chain going above swing arm (as is the case in vast majority of typical bicycles) not below.
Because my swing arm (same like yours) is not triangulated, I propose to have chain going under rear rear idler "B".
You can see the comparison here:

https://lh6.googleusercontent.com/-7U2RXoIx3gk/URzBQJ4BHsI/AAAAAAAANOw/ShoxNDUSCkU/s800/my_voyager.jpg

Of course I am exchanging problems with swing arm clearance for problems with seat clearance, but I am raising the seat as we speak :punk:

I will report the result when I am done and tested.

Ticktock
02-14-2013, 08:03 AM
Trust me, Adrians answer is the better answer, same as I suggest. The front pulley can come further back with no problems, and will sneak in behind the slightly raised seat, and leave plenty of room for the chain and bars to miss each other.
If you let the chain get any lower as it passes the pivot point, I think you will get problems with bounce. Aim to get the chain to just miss the swing arm when its on the 34 cog and on full bump--thats the best you can get.
Steve G