Lee Cooper Cycles might be able to help

http://leecoopercycles.terapad.com/
"CYCLE FRAME BUILDER.
Builder of quality built cycle frames. UNIT 4, THE SIDINGS, BIRDINGBURY ROAD, MARTON, CV23 9RX, TEL;01926 633 590"

What is the frame ? steal or alloy etc
If getting a frame blast cleaned (grit, bead, sand) and sprayed by a non-bike specialist (anyone in the yellow pages that just does anything and everything) then make sure that the BB threads are protected(leave old scrap cups in during cleaning and painting to prevent damage and over spray)saves having to clean the threads up afterwards. Also have a good look at the frame for cracks etc before painting, they are not so easy to find after painting.

Have a look at
http://www.hopegb.com/page_mep_force_57.html

Road bikes have a lower bottom bracket than MTBs and sometimes double sided pedals can just clip/ HIT the road, on roundabouts etc.

Saw this on the Highpath site under bike information http://www.highpath.net/
"Shimano rear derailleurs
Because their sprockets derail so easily, Shimano can fit weak springs in their rear mechs to make a lighter action. However derailleurs with stronger springs are more reliable in the long term and work better on sprockets with longer teeth.

Shimano derailleurs also have a floating top jockey wheel. You'll probably find that shifts are more positive if you replace this with a normal, non-floating jockey wheel."

Tony Oliver had a book called Touring Bikes which had some information on building / designing tandems, which will apply to tandem triplet.

http://www.vartools.com/catalogue_var.pdf
Kit de réparation des manivelles
Permet de faire un nouveau taraudage à une cote supérieure
(5/8’’x24 tpi) dans les manivelles recevant les axes de pédales
et donc de conserver vos manivelles.
Enduire l’extérieur de la bague réductrice de frein-filet
NL-77400 puis la visser dans le taraudage.
Enfin, replacer l’axe de pédale dans la bague taraudée.
Les tarauds s’adaptent sur le tourne à gauche DV-04330
Ce kit comprend :
– 1 jeu de 2 tarauds-aléseurs (D&G) 5/8’’x24 tpi
– 5 bagues taraudées pour manivelles droites
– 5 bagues taraudées pour manivelles gauches
– livré dans boîte compartimentée
PE-04703-5 – sachet 5 bagues 9/16’’x20 tpi coté droit (jaune)
PE-04704-5 – sachet 5 bagues 9/16’’x20 tpi coté gauche (grise)
A utiliser impérativement avec l'huile de coupe CD-77000-00250

9/16" x 20tpi (threads per inch)
Weldtite do what they call crank bushes and taps
http://www.weldtite.co.uk/pdf/weldtite_cyclo_tools.pdf

also Cyclus
http://www.cyclus-tools.eu/tretkurbeln.html?&L=3

Hope do RS Mono wheels.

Hope do a tool
http://www.hopegb.com/page_mep_force_58.html

thisisnotaspoon mentions car wheels, where opinions vary quite a bit
http://www.honestjohn.co.uk/forum/post/index.htm?t=82119

But on bikes there is stuff like: Ritchey Liquid Torque "Creates extra friction between two surfaces, allowing tightening torque to be reduced
by up to 30%.
Particularly useful for use where over-clamping can damage sensitive components such as Carbon bars or steerer tubes.
Approved for use with carbon, steel, alloy and titanium surfaces.
Use with Ritchey Torqkey to ensure safe installation of Ritchey bars and stems."

Effeto " Carbogrip

Carbogrip is a special high-molecular weight silicone resin that, sprayed on a component, creates a strong grippy surface.

HIGHLIGHTS:
– prevents part slippage and the consequent overtorqueing of the fixing bolts
– facilitates clamping of smooth carbon parts
– anti-seizing
– perfect as threadlock (steel, titanium, aluminum, carbon bolts)
– waterproof
– very easy to use: no need for brushes as with other assembly pastes/liquids "