UKC

I have grand dreams of building such a thing to carry the tandem I am yet to buy, and not spending £2-400 in the process.

Has anyone done this and got any advice?

My current plan is to get a 2m (or so, length yet to be confirmed) length of inch square aluminum box tubing, bolt it to the roof rack with u bolts, and use my uprights from my kayaking days, and some bits recycled from an old bike rack (gutter rests? Not quite sure how to describe them) to secure the wheels/frame etc. So far only about £30 spent. For £20 extra I can get myself a fork mount and QR skewer for a more secure fixing at the front.

Getting really fancy, I wonder about having the fork mount on some sort of swivel so I only have to lift the front of the bike up to the roof, secure it, and then swing the back up into place, much easier on my own. (Why you ask would I need to move the tandem on my own...?)

However, I can't find any sort of swivel unit that I could just bolt on. And I'm struggling to envisage quite how it could be done. Not helped by the fork mount by necessity sitting at 90° to the long strut.

I'm hoping to fix it all using nuts and bolts rather than any sort of welding, as I've never done it, don't have the kit or the contacts  and I'm trying to keep the cost down.

Any help/ideas/criticism/abuse gratefully received 

Cheers 

GTE

I've considered it but not got round to it as it always seemed more hassle than it was worth. 

Sounds like you are trying to to this on the cheap. https://www.sjscycles.co.uk/transporting-bicycles/atoc-tandem-topper-car-ro...

The front swivel needs to rotate on a vertical axis to swing the tandem to the side.

A vertical bolt will do that.

The front wheel swivel needs to rotate on an horizontal axis to swing the tandem to the up/down.

A front hub with a quick release skewer does that every time the wheel rotates and has the right dimensions & locking mechanism.

Imagine a couple  U bolts with saddles clamping body of hub to a solid aluminium plate about 10cm  square. The hub bearings allow rotation between axle tandem is clamped to and hub body.

In the middle* of the aluminium plate you have a bolt down into something clamped to the roof rack.

*eg in middle of the 4 holes for the u bolts so force from forks centred on the vertical bolt to minimise leverage

You might need to raise front hub 15cm to give clearance to the front chainring when swinging tandem on/off.

Any more photos or videos of what thepodge links to would help with that but looks like 15cm ish on the sjs site.

Having seen a bike fall off the back of a car on the A66 I'd encourage you to make sure to do a bloody good job of building it (if you are competent to design and manufacture it), if you are not competent I would just spend the money as the cost of an insurance claim for your bike rack failing might be quite significant...

On behalf of the poor bastard behind, who might get a face full of roof rack, I'd suck it up and pay the £200. 

A full Thule system won't be much more than £250. 

If it goes wrong, and injures or worse, kills someone, yo'll be in a world of shit. 

I have built such a thing

materials I  used

8ft of of 3"x 2" (1/8" wall thickness) aluminium alloy U channel

for the mounting hardware.   2x https://www.roofbox.co.uk/scripts/rbvehsel4_tab.php/car-specific-accessorie...

I didn't bother with the complexities of swivels to make lifting the bike easier, I'm 6' tall so was able to lift our tandem up onto the rack when it was fitted to my Vauxhall Corsa.

If I was doing it again I would use 2x Thule Proride 598 as donors for the support arms because they make it so much easier to load the bike, the clamping arm being the type that is open on 1 side.

I just had a standard pair of roof bars. Take the pedals off one side of the tandem, lock the handlebars  (rope or some mechanical device) and slide it onto the roof bars sideways (so that it is led on its side).  Strap down secureley to roof bars.