Low cost folding tandem on the train

Page may contain affiliate links. Please see terms for details.

brunobranson

New Member
Location
Frome, Somerset
Great article John!! Just done the rear wheel to get higher ratios, also would like to do the chain ring to get even higher. Now thinking about the stand, which relies on the front wheel staying straight as it is so far back.
 

Shrimpy

New Member
John, great write up. Thanks very much. I've just posted this as a reply to your write up and will copy it here:

I've just bought a new one this week (August 2020). I've been riding/building/modifying tandems and folding bikes all my life and have 35 years tandeming under my belt. Here is my take on gears:

Yes the current models come with the 14-28 freewheel and now a 36T chainring. This is a drop down from the 42T chainring on John's older bike. I assume this was to generate a lower hill climbing gear because, as we know, tandems do not climb so well. Trouble is, this gives a gear range of 25.71" to 51.43". This is fine uphill but useless anywhere else. Basically at 51.43" top you are really spinning at 9mph and have to coast at 10mph until speed drops. No good on a tandem. This is not a criticism of the product which is built to a price remember. So, what to do? Well I've considered ALL possible options and have concluded there is only one perfect upgrade for the bike which retains the very low hill climbing gear a tandem needs alonsgside an acceptable top gear for decent cruising speed. I have ordered the parts and will update here when complete and tested. First up is to ditch the 36T drive chainring and go with a 46T instead (yes there is frame clearance, just). This is a simple £13.72 upgrade from Ebay. Next is an 11-34 freewheel (Megarange) similar to John's cassette. If you can not go above 46T chainring (which you can't) on a 20" folder then you NEED an 11T sprocket, anything else is a pointless upgrade. Such freewheels are very rare and no longer made by Shimano because of the propensity to use a modern cassette. Of course, as John describes, a cassette needs a new hub and wheel re-build so a suitable freewheel is preferable if one wants a simpler solution. They can be found if you hunt around. Better still DNP make one especially for E-bikes with extra heavy duty freewheel components to handle the incredible torque generated by an electric motor. This is ideal for tandems that also generate double the torque of a normal bike. Said freewheel retails for £40 but is currently available on Amazon under DNP's new brand name of Drift Maniac for just £25.72 with free delivery. This is a bargain (e-bikes use standard freewheel hubs of course). Current link here:
Amazon product ASIN B07XZ64MJ8View: https://www.amazon.co.uk/gp/product/B07XZ64MJ8/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1


This combination of 11-34 freewheel and 46T chain ring maintains the very low gear for steep hills of just 27.06" whilst giving a decent top end cruising gear of 83.64". This range is ample for a 20" wheeled bike that has to manage on what is effectively only 6 speeds with an extreme 'granny gear' for when needed.

As for chains you should change this too. If you increase anything you should increase the chain length to match. The existing chain may work but only by over tensioning the rear gear pullies which in turn causes the chain to jump when on the biggest sprockets. The existing chain is 107 links and seems correctly sized so my upgrade to 34 tooth freewheel and 46 tooth chainring requires a new chain length of 115 links so a standard 116 link chain is an ideal option.

Hope this is of use to other Ecosmo buyers. The result is a good all-round compromise at a bargain price that means I have a tandem that folds in seconds and fits, would you believe, into the boot of an Astra hatchback with all seats raised!
 

BoldonLad

Not part of the Elite
Location
South Tyneside
To endorse @Shrimpy comments above.

I have made similar modifications ie: 11-34 FreeWheel (Drift Maniac), but with a 42T chainwheel, and, retained original chain.

This makes the bike much more pleasant to ride.

The Drift Maniac Freewheel is 11-13-15-18-21-24-34, so for the most part on reasonably level terrain, the first three gears give suitable speed/cadence (well, for us, two 73 year olds). I don't have accurate cadence figures, but, according to my Garmin Edge, pedalling at a reasonable cadence for us, gives 17mph on the 11 tooth cog, which is perfectly adequate for our "coffee and cake" rides ;)
 
OP
OP
johncantor

johncantor

Active Member
I recently wrote up our experience and modifications to an Ecosmo folding tandem. We took it to France on the train and had a great time.
This might be of interest to some.
http://foldingtandem.blogspot.co.uk/
A flurry of activity here on this blog. Some very good advice on how to improve the gears. Looks like e-bike quality cogs are an answer to wear-out-too-quickly items on a tandem
 
Top Bottom