Coupled Tandem

[iandusud]

The 50/50 split appears to have potential to make up overlapped as a psuedo solo for wheeling accros the station panniers in place and loading into a single bike space. So far I've not got this idea further than a few photos and scribbles. This might be a good way to go if the stoker can't deal with the luggage alone, as in Kim's post. If a train that takes bikes standing down on their wheels is part of a regular trip it would be worth putting some effort to make up the custom couplers for pseudo solo. They wouldn't need to be especially strong so lumps of plastic or plywood might do.

Once again thank you for your helpful reply. I didn't understand the above paragraph. Could you explain what you mean by "psuedo solo" please? With regards to the positioning of couplers I tend to agree with you with re two sets and it makes sense to me to position them so as to get two equal length pieces. I'm not too bothered about dealing with the timing chain. One thing I would like to achieve is a solution that will allow us to transport the tandem in a rented car without having to pay for a bigger car than we need for just the two of us.

Cheers, Ian

[MartynA]

The 50/50 split appears to have potential to make up overlapped as a psuedo solo for wheeling accros the station panniers in place and loading into a single bike space. So far I've not got this idea further than a few photos and scribbles. This might be a good way to go if the stoker can't deal with the luggage alone, as in Kim's post. If a train that takes bikes standing down on their wheels is part of a regular trip it would be worth putting some effort to make up the custom couplers for pseudo solo. They wouldn't need to be especially strong so lumps of plastic or plywood might do.

Once again thank you for your helpful reply. I didn't understand the above paragraph. Could you explain what you mean by "psuedo solo" please? With regards to the positioning of couplers I tend to agree with you with re two sets and it makes sense to me to position them so as to get two equal length pieces. I'm not too bothered about dealing with the timing chain. One thing I would like to achieve is a solution that will allow us to transport the tandem in a rented car without having to pay for a bigger car than we need for just the two of us.

Cheers, Ian

The idea is to bring the two halves together side by side overlapped so the extra frame length is lost but the bike will still wheel and pack in a solo space. It looks possible from holding the frame sections close with the front of the rear section pitched up at the front. So far only an idea and the design and making of adequate specific parts would/will take some work. Should I make any progress on this I will write it up.

About coupling protectors. I am using plastic bottle tops on the male ends, milk bottle and an old motor oil bottle, and cuts of foam insulation inside the female sleeves.

Fashion is for open frames but we are headed the opposite way with recent purchases of two double marathons. The coupled 2004 Thorn Discovery looks like a good buy with Reynolds 725 tubing 1.0 - 0.7 - 1.0 mm wall thickness so should be good for the rough and tumble of loading on trains and under coaches.  The paint is poor but I will patch it up for now also with rough and tumble in mind. The other bike, a Thorn Vittesse, looks like new and rides very well but is in need of surgery due to internal rust so I may enquire with Kevin Sayles at Woodrup as Jackson seems to be really gone after all.

[PhilP]

Reading the press yesterday, Woodrup are the purchasers of Bob Jackson, so maybe there is a chance of a new coupled tandem from them, although the article did mention 6 months delay before they start building again, and with a brand new workforce.
We have had a coupled Thorn, and in Oct 20, a coupled Bob Jackson. Both split in front of the captains seat tube, which negates the requirement to unship the timing chain. Time to split or unsplit, maybe 5 minutes depending on dexterity.
Using Ground Effect solo bike bags, our only train journey has been to Avignon, from Ashford and return, with the Thorn. It worked perfectly and circumvented Eurostar’s ban on tandems (several years ago). Big fan of couplings, once you have forgotten the price, they make a tandem easier to live with.

[iandusud]

Reading the press yesterday, Woodrup are the purchasers of Bob Jackson, so maybe there is a chance of a new coupled tandem from them, although the article did mention 6 months delay before they start building again, and with a brand new workforce.
We have had a coupled Thorn, and in Oct 20, a coupled Bob Jackson. Both split in front of the captains seat tube, which negates the requirement to unship the timing chain. Time to split or unsplit, maybe 5 minutes depending on dexterity.
Using Ground Effect solo bike bags, our only train journey has been to Avignon, from Ashford and return, with the Thorn. It worked perfectly and circumvented Eurostar’s ban on tandems (several years ago). Big fan of couplings, once you have forgotten the price, they make a tandem easier to live with.

Hi Phil, thanks for your comments. I have in fact been in touch with Kevin Sayle who is the frame builder at Woodrup and has also had a good stint at Thorn so is well acquainted with tandem building. It is our intention to ride over there once the lockdown is over to discuss measurement etc and place an order for a frameset. With regards to the placement of the couplers I can certainly appreciate the benefit of not having to remove the timing chain but I don't see us splitting it very often and suspect that splitting the bike into two equal lengths will make it easier to fit into a small hire car. (I think some disposable gloves will come in useful!).

Ian

[PhilP]

Ian, I've been through this loop recently, and ts often useful to know some numbers, for perspective.
Obviously your machine will have different dimensions, but just to give a ball-park idea.
Our Sapphire Pro measures 248cm end to end, with the 'long bit' measuring 165m, provided the cranks are vertical (the S&S is just in front of the pilots BB). Short bit 83cm. All measurements with wheels / mudguards racks.
So, if you split in the middle, its possible to have 248cm / 2 = 124 cms pieces, saving 41cms.
To achieve this length, you may need to also remove the stoker bars, since on our bike, they protrude over the half way point, making the front section longer than 124cms. Also unshipping the timing chain, as discussed above.
Hope that helps your decision making! (I spent hours discussing this with Ruth!)

[LittleWheelsandBig]

When I get a coupled tandem, my plan is to use a Gates belt as the timing chain. I really don’t like having to tweak my saddle position to compensate for timing chain wear and ensuring clean fingers when splitting the frame (behind the captain’s seat tube) has got to be an advantage.

[iandusud]

Ian, I've been through this loop recently, and ts often useful to know some numbers, for perspective.
Obviously your machine will have different dimensions, but just to give a ball-park idea.
Our Sapphire Pro measures 248cm end to end, with the 'long bit' measuring 165m, provided the cranks are vertical (the S&S is just in front of the pilots BB). Short bit 83cm. All measurements with wheels / mudguards racks.
So, if you split in the middle, its possible to have 248cm / 2 = 124 cms pieces, saving 41cms.
To achieve this length, you may need to also remove the stoker bars, since on our bike, they protrude over the half way point, making the front section longer than 124cms. Also unshipping the timing chain, as discussed above.
Hope that helps your decision making! (I spent hours discussing this with Ruth!)

Thank you. very helpful.

[iandusud]

When I get a coupled tandem, my plan is to use a Gates belt as the timing chain. I really don’t like having to tweak my saddle position to compensate for timing chain wear and ensuring clean fingers when splitting the frame (behind the captain’s seat tube) has got to be an advantage.

I've been thinking about a Gates drive for the timing for the obvious reasons. Having read the following article I'm not sure if it would be practical with coupling behind the front seat tube.
https://www.rodbikes.com/articles/gates-belt-drive.html
Ian

[LittleWheelsandBig]

When you split a coupled tandem, you can then pivot the two halves towards the belt side. That lets you remove and fit the belt without damaging it.

[iandusud]

When you split a coupled tandem, you can then pivot the two halves towards the belt side. That lets you remove and fit the belt without damaging it.

Interesting. Have you done this?

[LittleWheelsandBig]

Yes, a friend had a coupled tandem with a timing chain. Why would it be any different for a belt drive?

The Things OTP had a coupled magnesium tandem with a timing belt but I never saw them actually pack or unpack it.

[iandusud]

Yes, a friend had a coupled tandem with a timing chain. Why would it be any different for a belt drive?

The Things OTP had a coupled magnesium tandem with a timing belt but I never saw them actually pack or unpack it.

It sounds like quite a feat to align the belt, the cranks and the couplings simultaneously. The Rodriguez link says that you can't "roll" the belt on, as you might a chain. For the sake of some disposable gloves (which are a good idea to carry anyway) and ziplock bag for the chain I'm not sure it's worth the extra cost. I do however like the idea of a clean, low maintenance drive.

Ian

[LittleWheelsandBig]

It isn't difficult to do it with a chain. Why would it be particularly more difficult with a belt? The belt preload isn't huge.

Rodriguez is talking about rolling the belt onto a chainring and pulley at a fixed distance.

[iandusud]

It isn't difficult to do it with a chain. Why would it be particularly more difficult with a belt? The belt preload isn't huge.

Rodriguez is talking about rolling the belt onto a chainring and pulley at a fixed distance.

If I was doing it with a chain I would couple the bike first and then roll the chain on. 

[LittleWheelsandBig]

I don't. I set the timing chain a bit too tight to do that comfortably, to allow for frame flex under hard pedalling.

[PhilP]

I've had a Gates carbon drive on an uncoupled solo, and think if the timing belt was Gates, then it would simply slide off horizontally. Unlike a chain there is nothing to prevent them moving in a horizontal plane, apart from the width and rigidity of the belt. It would be great for a timing chain (?)
Gates timing chain wasn't an option for my BJ tandem, but I know Co-motion would supply these.
Of course, the cranks may need to be different left and right, if you have a timing Gates drive and chain final drive - maybe Middleburn could do this, I don't know, Co-Motion must have a solution. Costs start adding up.
As a drive system, I loved the Gates carbon drive.

Ian, re my post above on measurements - I wrote that without realising you already possessed a tandem, so I'm afraid it was a redundant post - apologies.

[LittleWheelsandBig]

Quite a few Gates belts now have a centre track, with chainrings/ pulleys to match, that mount to standard cranks and hub gear hubs.
https://www.bike24.com/p2141148.html
https://www.bike24.com/p2141237.html
https://www.tritoncycles.co.uk/components-c9/chainrings-sprockets-c69/centre-track-belt-drive-chainring-p17557

[iandusud]

I've had a Gates carbon drive on an uncoupled solo, and think if the timing belt was Gates, then it would simply slide off horizontally. Unlike a chain there is nothing to prevent them moving in a horizontal plane, apart from the width and rigidity of the belt. It would be great for a timing chain (?)
Gates timing chain wasn't an option for my BJ tandem, but I know Co-motion would supply these.
Of course, the cranks may need to be different left and right, if you have a timing Gates drive and chain final drive - maybe Middleburn could do this, I don't know, Co-Motion must have a solution. Costs start adding up.
As a drive system, I loved the Gates carbon drive.

Ian, re my post above on measurements - I wrote that without realising you already possessed a tandem, so I'm afraid it was a redundant post - apologies.

As mentioned above the Gates drive now uses a centre track. Re your comments on measurement, not at all redundant - very helpful.
Ian

[Russell]

My issue with a Gates drive belts is that they come in fixed lengths meaning that you need specific size rings and bottom tube lengths.  We are small folk, Mrs R particularly so, so we specified a shorter bottom tube to suit, saving length, weight etc and so we cannot have a Gates.  We need to run a half link unfortunately.

[Joe.B]

It has been interesting to read through the previous comments about Gates Belt Drives for the timing as I’ve wondered about this on and off for quite a while.
The biggest obstacles seem to be the fixed length, (though less of an issue if you keep the eccentric BB), and the fact that those chainrings and cranks aren’t cheap. 

[LittleWheelsandBig]

A tandem with a timing belt needs an eccentric to set the correct belt tension.

By the way, if you need a half-link to keep your timing chain within the range of your eccentric, changing your timing chainrings for ones that are one tooth larger or smaller should bring you back into the adjustment range of your eccentric. Costs more than half-links though.

There are a couple of riveted split belt systems that allow custom length belts (particularly for tandems and retrofitting to unmodified bike frames), though I've not seen any of them in the flesh.
https://www.veercycle.com/collections/all/products/split-belt-pro-belt-drive-for-tandem?variant=29894672154702

[Russell]

There are a couple of riveted split belt systems that allow custom length belts (particularly for tandems and retrofitting to unmodified bike frames), though I've not seen any of them in the flesh.
https://www.veercycle.com/collections/all/products/split-belt-pro-belt-drive-for-tandem?variant=29894672154702

Very interesting, will seriously consider it when the timing chain needs replacing.

[Russell]

Had a look into this and while it would be nice it would work out very expensive.  There's the £300 odd for the tandem kit and then as I run Middleburn RS7 cranks with direct fit chainrings, I'll need to buy 2 spiders as well at an additional £60 something each.  We'll be nudging £500 in total.   

I've contacted Veer to ask if they have plans to produce compatible belt rings, there's a precedent as they make compatible rear sprockets for hub gears.

Having said that replacement chainrings are £97 ea!

[LittleWheelsandBig]

Tandem coupler options are pretty limited.

S&S couplers are the most common by far. I still have my coupled solo which was built for PBP99. Couplers are heavy and expensive. They stick out beyond the tube width, so the top tube coupler rubs against my thighs, which irritates during long brevets.

The Ritchey Breakaway system is lighter and a bit cheaper but relies on the friction of painted surfaces to transmit torque. The coupler components appear a little undersize for tandem down tubes. The interfaces with the frame tube don’t seem to have lots of additional area like S&S lugs do. I don’t know of any tandem builders offering this, other than Ritchey’s own tandem offering in one size only.

Santana’s couplers allow for oval bottom tubes and are flush with the tube surface but of course cannot be retrofitted and tie you into their complete system (160mm rear axle spacing and the rest).

http://www.groupj.net/blog lists a BFC coupling system that I hadn’t seen before - basically a Ritchey/ S&S hybrid. Given that the website has not been updated for five years, I guess it got a cease and desist order or otherwise went pop. A pity as it looks like a viable option for retrofitting.

No.22 do concealed frame couplers with hydraulic line separators but they are only fitted to their own bikes and aren’t tandem-compatible. https://22bicycles.com/blogs/news/introducing-our-all-new-coupler-system

[Russell]

I've contacted Veer to ask if they have plans to produce compatible belt rings, there's a precedent as they make compatible rear sprockets for hub gears.

To square the circle here, I've had a reply from Veer who say that they do have plans to manufacture direct fit beltrings but cannot give a timescale as they have other projects lined up first.

Watch this space  suppose.