Crafting our custom bikes to shape your next Islabikes

Islabikes is best known as the innovator in the children’s cycling market. At our workshop in Ludlow we have the expertise to design and build bespoke bicycles. Fuelled by our workforces’ passion for cycling and a wealth of engineering know-how, we craft one-off frames to ride and use as test beds, shaping new products and designs in our children’s range. Here, Islabikes’ in-house frame builder, Robert ‘Keen’ Burns takes us through the different stages involved in creating one of these masterpieces.

These incredible machines are only available for Islabikes colleagues – if you want one, you’ll have to come and work with us!

The design process and tube selection

The intended rider of the bike sits down with Islabikes’ founder Isla Rowntree and discusses what kind of bike they want. Then, Isla will look at the person sitting in the saddle and decide what tube lengths and frame angles their new bike will need in order to design their bike. A specific tube set will also be chosen according the the person’s riding style and bodyweight.

Islabikes’ custom builds use steel tubes from Reynolds, a famous firm based in Birmingham. Tubes come in a vast array of sizes in either standard form, plain gauge, or butted. Butted tubes are thinner in the middle and thicker at the ends which isn’t noticeable from the outside, as the external diameter remains the same. Butting saves weight whilst maintaining strength where it’s needed. This is reflected in our children’s bikes, which are all designed with butted tubing, making them light and strong.

We typically order Reynolds 953, 853, 725 and 525 tube sets for our custom bikes as they are specifically designed for modern framesets and TIG welding. Keen says:

“Old Reynolds 531 tubes had quite a high manganese content. There is a lot more chrome in the tubes now, which makes them a lot stronger and stiffer. So modern tubes, such as the 953, are 10 times stronger but they look exactly the same as those old tubes.”

Custom builds at Islabikes

Cutting and mitring

Isla gives Keen a drawing of the frame design and, once the tube sets arrive, he starts marking out the tubes, identifying where the butted profiles are. Normally one butted section will be longer than the other, so Keen has to orientate the tubes to match the butt profile with the design and have the strongest of the tubes where they are most needed.

Then Keen can mark out which bits he’ll cut off, roughly to length. He cuts and mitres the tubes by hand, using files and hacksaws. Although he does have a small lathe for drilling and machining, Islabikes’ custom frames are almost entirely hand built. Whichever sort of tubes Keen is working with, he puts them together in exactly the same way. With the bottom bracket shell in the jig, he will start by creating the seat tube joint. Keen will do the mitring, filing the tube ends perfectly to shut out any daylight, then tap the joints together.

Cleaning

Before Keen can start welding, the tubes have to be scrupulously clean. He cleans the inside with acetone and has a die-grinder to get everything nice and bright. If a tube is handled with bare hands, ever-present finger grease can compromise the weld, so it has to be clinically clean.

It’s also important to keep the general welding area free from draughts. Keen uses a TIG welder to create our custom frames. This requires the area being welded to be ‘clean’ of oxygen, which will cause the weld to crack. To achieve this, Keen has to ‘back purge’ and get inert, clinically clean argon has inside the tubes as well as on the outside where he is welding. Keen has adapted his argon gas bottle and fitted it with a dual outlet on the regulator, so a tube taking argon gas can be placed inside the frame, with all holes blocked off.

Welding

Now it’s time to start welding.

After mitring the bottom bracket shell and seat tube in situ, Keen removes them from the jig and welds the joint freehand. The TIG welder has a tiny Tungsten blade sticking out, which is a small electrical flame shrouded in argon gas that keeps oxygen away from the weld pool. This little electrical flame goes around the joint and Keen uses a filler rod to make the weld smooth. Because the tubes’ wall thicknesses are so thin, Keen’s filler rod is actually less than 1mm thick – it’s almost like a run of paint going round.

TIG welding removes the need for lugs, which makes for lighter frames because you don’t have tubes fitting inside other tubes. That also means we are not constricted by predetermined lug shapes and allows us to use any frame angles we like. Another benefit of TIG welding is that, unlike brazing and lugs where the weld filler effectively glues the metal tubes together, a TIG weld actually melts the molecules of the parent tubes and joins them directly together. This makes TIG-welded frames particularly strong. The filler rod only acts as a catalyst to help join the tubes together and makes things neat.

TIG welding only uses very intense but localised heat, rather than more widespread heat, so it doesn’t deform the tubes or destroy their inherent strength. That’s why we use specific Reynolds tubes made for TIG welding – the very edges of the tubes bond as one.

If you add heat to any tube set it will bend but by welding freehand, Keen can manipulate the tubes the way he wants. If he spots a tube is pulling slightly to one side, he can alter his weld pattern and weld to the other side to compensate. That way he can keep things absolutely straight, so there is no bend in the cold setting of the frame after the weld.

Keen says:

“It’s a proper craft but it’s a nice process when you get the weld absolutely lovely because it’s so neat. You don’t get the big shells, the stack of dimes as you get on a welded aluminium frame.”

Custom builds at Islabikes

Working round the frame

Keen will start with the weld between the bottom bracket shell and the seat tube, then move onto the bottom bracket and down tube. From here he’ll fit the head tube ― either a 1 1/8 inch head tube or a new 44mm head tube, which will accept a modern 1 ½ inch to 1 1/8 inch tapered steerer tube for added strength. After that he’ll fit the top tube before moving on to the rear triangle, first with the chainstays and then the seatstays.

The stays may need more than just welding. If Keen is making a mountain or cyclo-cross frame he may have to manipulate the tubes to allow for tyre clearance. This is where Keen’s background as a tool-maker comes in helpful, as he has created all the jigs and fixtures he needs to bend or dimple the tubes into the required shape.

Keen says:

“Isla uses a lot of narrow chainsets, so a bike might have a very low Q Factor and I’ll have to really bend the seatstay in for heal clearance, before bending it back out again to accept the 130/135mm (mtb) rear end. But all this relates directly to the research and development we need for our children’s bikes.”

Custom builds at Islabikes

Finishing off

When the frame has been welded together, Keen will go all over it with Scotch Brite looking for any imperfections. Then he’ll chase the head tube and bottom bracket shell so they are ready for the headset and bottom bracket to be fitted when it comes back from being painted. Islabikes’ custom-made frames are painted by Euro Quality Coatings in South Wales. It’s a two-stage process with a phosphate finish, which stops any rusting inside the tubes. Then the frame is given a super hard powder outer coating.

Keen says:

“It’s not a glossy paint, it’s more of a satin finish. Turkish Green is my favourite colour. We pop the frame in a box with a delivery note and a colour choice and then three days later we get the frame back. We put the decals on between us, so that everyone gets a little bit of experience of the bike-building process. Then it’s all ready to be built up with whichever components have been chosen and the excitement really begins!”

Islabikes’ man with the TIG welder: Robert ‘Keen’ Burns

‘Keen’ is 54 and before working at Islabikes has worked in engineering ― tool rooms, foundries and maintenance departments ― since he was 15 years old. He’s also been a lifelong cyclist and, as a grandfather, can boast that he now has three generations of his family all riding Islabikes.

“All I do of an evening is study other welding techniques, I don’t watch telly anymore!”

Custom builds at Islabikes

Choose your Islabikes site

GB Flag

You are visiting the UK-English Islabikes website

German Flag

Would you like to visit our German website?

German site
German Flag

You are visiting the German Islabikes website

GB Flag

Would you like to visit our German website?

English site
GB Flag

You are visiting the UK-English Islabikes website

USA Flag

Would you like to visit our US website?

USA site
German Flag

You are visiting the German Islabikes website

USA Flag

Would you like to visit our US website?

USA site