[RiderInTraining]

I really liked the setup that Mountainboat had on this Monocog - single cog and triple chainring. So I got myself a Melvin and put everything together.

I planed on using a 19t cog, but that's where the problem starts. The space between the cog and the upper pully is so narrow that the chain won't fit through it without trouble. I use a 17t right now and everything works fine. I might be able to squeeze a 18t in there, but even that's a pretty high gear for me on a 29er.

My questions now... is there anything that I could have done wrong by setting up the Melvin? Does anyone know if the Rohloff chain tensioner would work the same way and would offer more clearance?

Any help would be much appreciated.

 

[flipnidaho]

I really liked the setup that Mountainboat had on this Monocog - single cog and triple chainring. So I got myself a Melvin and put everything together.

I planed on using a 19t cog, but that's where the problem starts. The space between the cog and the upper pully is so narrow that the chain won't fit through it without trouble. I use a 17t right now and everything works fine. I might be able to squeeze a 18t in there, but even that's a pretty high gear for me on a 29er.

My questions now... is there anything that I could have done wrong by setting up the Melvin? Does anyone know if the Rohloff chain tensioner would work the same way and would offer more clearance?

Any help would be much appreciated.

Look at SIGMA's setup further down the thread. That is the proper setup for the Melvin (looks like a derailleur). I set one up for my SO's bike that has a 20T cog with no problem (for a 2X1 setup)...

 

[PeanutButterBreath]

But what does it look like when the chain is on the 42 up front?

I had the same issue as OP with the Melvin. Weird.

 

[flipnidaho]

But what does it look like when the chain is on the 42 up front?

I had the same issue as OP with the Melvin. Weird.

The pulley cage is horizontal (or close to it based on the amount of chain you kept). The original Monocog setup on the referenced thread had the Tensioner setup incorrectly. Once it's on the bike and the chain is in the smaller chainring, the Tensioner should have the pulley cage pointing straight down. The pulley cage works just like a derailleur pulley cage.

 

[RiderInTraining]

Well, SIgma is using only two chainrings. Mountainboat is using 3 and my Melvin looks pretty much like his when in the small and middle chainring.
I still can't figure out why my 19t cog won't fit.

 

[PeanutButterBreath]

When the cage was pointing straight down on my bike, there was contact between the upper pulley and a 19T cog.

 

[RiderInTraining]

PeanutButterBreath, same with my setup. The funny thing is, that if you look at Mountainboat's setup, he's using a 20t cog and still has room between the cog and the pulley. I don't know if his derailleur hanger is longer or if there's a different version of the Melvin with a longer arm or what.

 

[madonenm]

Works for me...

My setup works just fine with a melvin and a 19T freewheel. Take a look at the following thread (http://forums.mtbr.com/showthread.php?t=252176) for some details on my setup.

 

[madonenm]

PeanutButterBreath, same with my setup. The funny thing is, that if you look at Mountainboat's setup, he's using a 20t cog and still has room between the cog and the pulley. I don't know if his derailleur hanger is longer or if there's a different version of the Melvin with a longer arm or what.

I don't think there are different melvins but the derailleur hanger might be the issue. What is your rear dropout configuration (i.e. track ends with hanger, sliding dropouts, etc.)?

 

[mountainboat]

works for me.....

I run a 20t Surly cog with my Melvin with no problems. It's real close, but no contact. I had a 22t Surly cog, but had problems with contact like you mention. Also, the stock singlespeed cog that the bike came with had a taller tooth profile. It didn't work as well as the Surly, but was functional.

Setting up the chain length properly and staying within the 22t difference limits of the Melvin is a key point of making a 3-speed set-up, such as mine, work properly. I'm pretty sure the difference limit for the Melvin is 22t. Although someone stated 20t in a different thread. I run mine with a 20t difference to avoid the extremes of tension on the pulley cage. It sure looks like I could run another couple teeth difference though, based on the position of the pulley cage in the low gear.

flipnidaho-

I think you are mistaken that the tension on my Melvin is set-up improperly. Or to put it another way, that my chain length in incorrect. Reference the drivetrain close-up at the bottom of the thread, and you will see that the pulley cage is pointing vertically when in the middle ring of my 3-speed. This allows me to downshift without the pulley cage traveling back so far that the chain rubs on the cage, and I can upshift without putting so much tension on the chain that it pulls the pulley cage too far forward.

RiderInTraining-

My initial thought on your problem with contact between the cogs, is that it may be due to the relationship of your derailleur hanger to the wheel axle in the horizontal plane, but that is just a guess without knowing your dropout configuration.

What kind of chain and cog are you running?

A photo of your set-up would help.

One thing I notice in the photos of other's dinglespeed set-ups, is that the arm on my Melvin, that replaces the paralellogram on a derailleur seems, to be pointing down more on my bike than other folk's bikes. This would be due the geometry of the derailleur hanger itself, or it could just be the angle of the photos. This would drop the pulleys on my bike further away from the cog. The angle of this arm is not adjustable on a Melvin like it is on a derailleur.

I've never tried to run a Rohloff tensioner before. I would look into how much the tooth differential is for one before I considered ordering it, since the chain length of a Rohloff hub set-up doesn't change. The tensioner for the new Shimane Alfine internal hub looks like an interesting option too.

 

[totally_fixxated]

Melvin/Rohloff

Does anyone know if the Rohloff chain tensioner would work the same way and would offer more clearance?

The older Melvin would work alot better than the new one, since it pivots right next to the top jockey wheel(pulley).

Compared to the new one that pivots below the top jockey wheel, moving the jockey wheel closer to the cog as you tighten the chain.

You could also adjust the spring preload by moving the spring tang to one of five different holes on the older one.

The Rohloff pivot is through the top jockey wheel, keeping the distance from the cog the same no matter if you loosen or tighten the chain.

View attachment untitled.bmp *New Melvin*

 

[flipnidaho]

flipnidaho-

I think you are mistaken that the tension on my Melvin is set-up improperly. Or to put it another way, that my chain length in incorrect. Reference the drivetrain close-up at the bottom of the thread, and you will see that the pulley cage is pointing vertically when in the middle ring of my 3-speed. This allows me to downshift without the pulley cage traveling back so far that the chain rubs on the cage, and I can upshift without putting so much tension on the chain that it pulls the pulley cage too far forward.

My bad, I didn't read the OP thoroughly. I was thinking that it was a 2 ring setup not a 3... Carry on...

 

[RiderInTraining]

OK, I tried an 18t cog, it's a no go as well. It fits in there with just enough clearance, but another problem seems to be the alignment of the cog and the pully.

Even though it looks OK without the chain, as soon as I start putting pressure on the chain when I pedal, the chain starts to slip pretty bad. I think, it's because the Melvin is flexing a little, which throws the alignment off, which causes the teeth to miss the chain by just a little. With a 17t cog, it's not a problem because the larger space between the cog and the pully compensates for it. At least that's what I think is happening.

Next thing on my list is the Rohloff hopping that it gives me more clearance between the pully and the cog. If that doesn't work I can build my own derailleur hanger or just ride a 'real' single speed.

Here are the pictures of my set up...

 

[SIGMA]

I bent the hanger.

i stood behind the bike and used an adjustable wrench to bend the hanger toward the the rear of the bike.:eekster: the melvin has no screw like a derailluer to move it back.i just pulled it back till it cleared the jockey wheel. it didnt break,the aluminum is pretty soft.

 

[totally_fixxated]

One chainring too many?

At least that's what I think is happening.

http://www.paulcomp.com/techmlv.html

4a. For bikes with two front chain rings, cage should be in an approximately straight up and down position in the smaller of the two chain rings. This set-up will probably require stepping up cage tension, see (5.)

I would try to line-up the rear cog with the middle chainring, if it is offline and see if that helps? Then recenter the tensioner, if needed.

If that does not work, I would lose the BigRing!

 

[RiderInTraining]

Problem solved. Turns out that my LBS is some kind of genius. He suggested to move the cog further out on the cassette. I still don't quite understand it though.

To me it looked just fine the way I had it before. Also, I would think that this alignment is not really THAT critical in my case, since it's not a real single speed. I mean the chain runs through the tensioner first, so it seems more important to line up he pully with the cog. But hey,... I stand corrected.

I'm just really happy that it works now. Thanks again to Mountainboat and Madonenm to share their set-up.

 

[mountainboat]

Problem solved. Turns out that my LBS is some kind of genius. He suggested to move the cog further out on the cassette. I still don't quite understand it though.

To me it looked just fine the way I had it before. Also, I would think that this alignment is not really THAT critical in my case, since it's not a real single speed. I mean the chain runs through the tensioner first, so it seems more important to line up he pully with the cog. But hey,... I stand corrected.

I'm just really happy that it works now. Thanks again to Mountainboat and Madonenm to share their set-up.

Glad to see you were able to work it out.

Welcome to the "Simpleton" drivetrain club.

Here's a shot of the tensioner I want for my next 3 speeder. Looks like it might have more adjustment:
https://photos1.blogger.com/blogger/4881/1620/1600/Alfine.jpg

 

[RiderInTraining]

I've looked at the Alfine as well. You'll find a better picture here.
You can already get it on ebay for a little over $20 plus shipping, if the guy is willing to ship it to the US.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=009&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=190075899106&rd=1&rd=1