Tension of "Captain" (Lhs) chain on Tandem

[Guest Big H]

I hope one of our boffins can help. We have Sugino XD drive train on our Tandem. The two spiders for the long chain (chain from captain on left hand side) have Sugino 44 teeth chain rings on them. I cannot get the chain tension set properly. The chain was way too tight?? almost no play on it. I cut the chain and added one small link and one large link. The chain now has way too much tension play. There is approximately 80 ? 90 mm tension play.  We have a 7.7mm ?captain? chain on the tandem?? measuring across the rivet. The permissible available cam length on the front BB to adjust chain tension seems to be about 8mm measured horisontally and that is more than the 25.4mm of a chain link (both large and small side plate)<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Is this a function of the large 44 teeth chainwheels?????

Our previous drive train on el rapido was the normal crank set found on the steel framed Peugeots. It had a smaller chain ring and I was able to set the chain tension properly.

If so what size chain ring must I put on? The chord length of the five spider crank arm is 64.6mm which equates to a 110 mm BCD.

Any help would be appreciated as I want to order things from www.chainreactioncycles.com and want to include the chain rings in my order.

Big H2008-12-29 03:07:37

[turtlek]

I had a similar problem with one of the tandems i serviced a while back

 

 

 

when you turn the cranks does the chain in any way become loose or does it stay stiff through the whole revolution??

[Johan Bornman]

No, it has nothing to do with the chainrings. A tandem's cam can't give you as much adjustment as two links (one inner and the obligatory outer) add to the overall length. You are just unlucky with the distance between captain and stoker BB.

 

I suggest you put on a standard 8-speed chain - single speed if you can find and add a half link like this:

 

 

This will than bring the cam within the adjustable range.

 

The trick is to fit a wide single-speed chain on there to justify the cost and expense of finding a half-link. That excellent chain company, KMC makes half links but others too. They even make an entire chain comprising half links.

 

 

 

 

Johan Bornman2008-12-29 03:10:31

[Guest Big H]

Thanx Johan, It has a KMC chain on at present. Do you purchase the half link seperately (of coarse as seen from the pic) and where can I get one? Where can I get the single speed chain?

[Johan Bornman]

Thanx Johan' date=' It has a KMC chain on at present. Do you purchase the half link seperately (of coarse as seen from the pic) and where can I get one? Where can I get the single speed chain?[/quote']

 

I should have said "track chain" (as in singlespeed track bike). It is a 1/4 inch (8mm) chain that doesn't flex laterally. However, first try and get the half links and then buy the chain accordingly. You may even get a half link for the chain you're using now.

 

Where to get the chain? Any competent bike shop should have track chain. Otherwise, CRC I suppose.

 

Those same competent shops should have 1/2 links in stock or should be able to get some for you. I don't buy the stuff since I have a 1/2 bike, so I can't say where. Shop around or ask the guys at Harris Cyclery (www.harriscyclery.com) to send you the chain and link. If it exists, they stock it.

 

 

 

 

[Johan Bornman]

I had a similar problem with one of the tandems i serviced a while back

when you turn the cranks does the chain in any way become loose or does it stay stiff through the whole revolution??

 

Have you somehow managed to put a Biopace ring on one of the cranks?

[turtlek]

I had a similar problem with one of the tandems i serviced a while back when you turn the cranks does the chain in any way become loose or does it stay stiff through the whole revolution??

 

?

 

Have you somehow managed to put a Biopace ring on one of the cranks?

 

 

 

Nope funny enough they had used FSA chainrings that were made for a compact crankset on the captain chain and in doing so they had overtightened the chain with the cam and due to the pressure or torque (not too sure which one is correct to use in this instance) after a few rides the rings had been deformed into an oval shape causing a tight spot in the chain

[Guest Big H]

We are now back in Angola. I fitted the two 39 teeth chainrings last night...... the Tandem previously had 44 teeth rings...... and viola!!!!!!! the chain can now be properly tensioned!!!!!! .......... by the way ..... I also ordered the half links so I now also have a "cheap" optoion available.