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Jake Robbins Girder Forks

Repairs & Manufacture

Jake Robbins talks about his girder fork engineering business, and shares his insight into girder forks care, repairs, maintenance and manufacture

(Part 1)

 

▲ Jake inspecting his replica Castle girder fork in his workshop—an old blacksmith's foundry near Hastings in East Sussex.

 

Jake Robbins remanufactured Castle Forks

 

Girder fork components

 

Jake Robbins in his workshop

 

Fork spindles awaiting repair or replacement

 

Bronze bushes for girder forks

 

 

Girder fork damper knobs

 

 

Jake Robbins retubes, rebushes and re-casts fork components

 

 

Another finished set of Castle girder forks

 

Jake Robbins - girder fork specialist

 

Telephone: 07986 254 144

Email: elkforks@aol.com

www.jake-robbins-vintage-engineering.co.uk

 

Jake Robbins began his career as a girder fork engineer working with the late Steve Burniston, the man behind Elk Engineering. Steve died in 2002, leaving Jake to continue the business which has gone from strength to strength. Now trading under his own name and operating from a workshop in Hastings, East Sussex, Jake explains some of the intricacies of the girder fork and shows how to maintain and get the very best from them.

"I’ve always had a passion for bikes. My older brothers all had British motorcycles, while I had Italian machines mostly. Currently I run a Ducati 250 café racer and a BSA B50 fitted with a Rotax 500cc engine. It was 1990 when I began working with Steve.

"Steve had amassed a considerable collection of girder forks and needed an engineer to help develop the business. There were various jigs to be built and equipment to be sourced.

"The work back then was mostly straightforward reconditioning of spindle bushes, but I now re-tube and remanufacture forks, and also
re-tube and repair frames. But girder forks are my core business.

"I offer a fixed price for re-bushing and re-spindling the more common types of girder forks, such as BSA M20/M21, Norton and Velocette Webb types. The price is between £200 and £250, and the work includes new knurled washers, friction discs, and pretty much everything that wears and looks tatty.

"People often send me pictures for quotes and appraisals, and I’m happy to do this. There are hundreds of forks out there, and even for an expert it’s not always easy to tell one from another. But I’ve got plenty of experience and lots of reference material and can usually work out what’s what.

"I supply some spare parts, such as spindles and bushes for people to recondition their own forks. I make front wheel spindles too where required."

 

 

Inspecting girder forks in situ

 

"The best way to check the forks is to fit them to the bike and rock them back and forward whilst applying the brakes. You need to watch the upper spindle areas and listen for any clicking.

"Earlier bikes without a front brake really need two people for this check. It’s important to load up the bike a little to replicate how the forks behave under load, and not how they behave in the garage.

"You need to watch the side plates too and look for uneven lateral movement. But take care that the side plates on the girders haven’t been overtightened.

"People do that sometimes thinking it will take up wear and/or hoping to slip the bike through an MOT. In fact, all it does it mask wear and it damages the side plates. There has to be a small clearance. When forks have been abused like this, they need to be stripped and have the worn surfaces built up with weld.

"Also, you should stand with your legs on each side of the front wheel and twist the bars against your legs and feel for play. There’s a fair amount of latitude, but ideally there shouldn’t be any play at all."

 

Inspecting dismounted girder forks

 

"Usually you can tell good forks by the way they ring or rattle. It’s similar to railway engineers clanging train wheels to listen for dull spots. Your ears can tell you a lot if you just listen carefully.

"You get an eye for it too. When I get a set of forks in for repair, I check them in a variety of ways. I look for squareness. I feel the tubes and lugs searching for damage. I give them a good rattle and listen for rust particles—or larger pieces—moving around inside.

"Naturally, it’s harder to do these checks when the forks are fitted to the bike. I also inspect all threads and lugs—both of which are easier to repair effectively when the forks are off the bike. So take advantage of strip-downs and restorations.

"Many of these checks can be performed by owner riders—and riders should also constantly monitor the way their bike performs on the road which, with a little sensitivity, will give long advanced warning of problems."

 

Girder fork springs

 

"The quality of girder fork springs is important. A breakage could, at worst, lead to a collapse and cause the front wheel or front mudguard to slam into the frame leading to a total loss of control. So always check the springs—especially with regard to the earlier Druid type forks that effectively hang on the spring.

"You need to look for obvious damage. Cracks, for instance. Or severe pitting or rust. Or thinning areas—most likely at either end of the spring rather than in the centre. Check too for uneven coil widths and that the spring is compressing evenly and not skewing to one side.

"Later forks with a central compression type spring (such as those fitted to military BSA M20/M21s, or pre-war Triumph Speed Twins—think of them very broadly as Webb type) are not quite so likely to break a spring. But it can happen. So check regularly."

 

Hidden cracks in girder forks

 

"I once had a set of Vincent Brampton forks, (not to be confused with Vincent Girdraulics), and although they looked absolutely perfect externally, there was rust weeping around the lower casting on the fork blade. One blade had completely fractured through age and internal rust, which was obviously dangerous. Luckily, the owner quickly realised that something was wrong.

"I retubed the fork completely (which means removing the tubing from the cast lugs) and the bike is now back in service. It really pays to watch for these kind of cracks. Rust can be a useful indicator.

"The parts that held the tubes together were cast or dropped forged —but usually cast. They do crack and corrode, but damage is usually due to accidents."

 

Girder fork spindles & bushes

 

"Girder fork spindles are usually made of EN16 or EN24T steel. It’s a high carbon hardened steel with a slight springiness that allows it to flex a little. You might say that it has a “good memory”. This type of steel is important, because brittle steel would simply snap under heavy use.

"Girder fork bushes were originally a high copper-content phosphor-bronze type. It was good enough in its day, but I use Oillite bushes. Oilite bushes are made from compressed granular beads of phosphor bronze impregnated with oil. As you machine these bushes, some of the oil comes out. But it also means that the bush will hold an oil lubricant better. Think of it as a bronze sponge.

"Girder forks bushes have an interference fit, which means that they are designed to be very tight in the spindle bore hole. However, once pressed into place, the compressive forces invariably squash the bushes undersize. This means that the bushes need line-reaming – which re-cuts the bushes to an exact, fitted size. I make my own reamers and modify them to suit.

"Occasionally people try to deal with wear in the spindle bushes by fitting homespun shims, such as bits of aluminium or even bits of steel take from ordinary tape measures. I’ve seen many other examples. But re-shimming isn’t going to really help, except perhaps in the very short term.

"Girder fork spindles wear oval. You need to either remove the worn bushes and repair in the proper way; or, where appropriate, rebore the spindle holes and fit oversize bushes.

"Bodges that might work on the bench won’t necessarily work on the road. The result will be sloppy—and perhaps dangerous—handling. Be warned.

"Bush-to-spindle clearances vary from fork to fork. It’s hard to specify exact clearances because girder forks themselves simply aren’t precision enough, certainly not after fifty or sixty years on the road, and you have to be sensitive to the application. What is important is that the spindles have a good sliding fit. Not too tight, and not too loose.

"Much of what I do is actually by feel and eye. The work is somewhere between an engineers and a blacksmith. Aas I said earlier, there is a fair amount of latitude here. You have to be realistic."

 

Girder fork and frame straightening and repair

 

"The next major aspect of my work is straightening and repair of road damage. For instance, I recently had a Sunbeam Model 9 in the shop that had been in a shunt. I worked for the insurance company and collected the bike, estimated the costs, got the “okay”, and rebuilt and retubed the forks. The frame also needed straightening, which I handled too. The job took about 8 months from beginning to end, but much of that was waiting for the okay from the insurance."

 

Retubing girder forks

 

"Retubing a set of forks would normally take 3-6 months. It sounds long, but the tapered tubing isn’t available off the shelf. I have to buy in the tubes and send it off to be tapered and altered to suit each specific job.

"It’s all Renolds type CDS (cold drawn seamless) tube, which is high carbon steel and pre-annealed—which means that the steel has been softened so that it can be tapered.

Tapering builds up the wall thickness in critical areas. No material is actually removed. It’s all just pushed into shape, like squeezing plasticine."

 

Finishing Girder Forks

 

"Forks can be finished in a variety of ways. Traditionalists might want to use enamels or cellulose. But most people these days will opt for a good two-pack paint or even powder-coating. Modern powder coating is actually quite good. The steel is etched primed and heated treated. The final coat is quite thin, which is what you want, and it looks like enamel."

 

Read Part 2 ►

Part 2 includes information on various types of girder forks and advice on general maintenance.

 

Jake Robbins

Girder fork specialist

Telephone: 07986 254 144

Email: elkforks@aol.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 











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