Wednesday, March 19, 2014

More Fenders

Steam chamber and old bending jig.
 So, I've been monkeying around with bicycle fenders for some time now. It all started out of necessity really. My plastic fenders would eventually crack in half, so I would splice them back together only to have them fail again eventually.

My first attempt at a less destructible  fender was made from flat 1/16 x 1 1/2" aluminum stock which I bent in the shape of the wheel and then riveted the old mounting hardware to. These worked pretty well but were also really flexy. A better choice would have been to use full 1/8" aluminum stock or to add a rib or channel to the aluminum. Both of those options require either equipment that I don't own or have access to, or time to build the right die/mandrel to stretch the fender around.

New bending  jig.
For the second attempt, which was last year, I decided to try and make some wooden fenders. It seemed like it should be pretty easy and I already had most of the woodworking equipment. I just needed to build a form to dry the blanks on so that they would hold the curve. For this I used an old rim with some wooden blocks that I screwed to it. The blocks spaced the diameter out to the radius I needed for the finished fender.

At this point I used the saturation bend technique, which meant I soaked the wood in the bathtub for a couple of days and then wet bent them against the mold. To keep them in place I clamped them and then left them to dry over the heating vent. This worked OK, but not great. The wood was not nearly as pliable as it really needed to be and although I did get a distinct bend, the curvature was not quite as tight as I would have liked. This meant that when the fenders were installed, they had a little bit of spring to them. It turned out that there were some actual benefits to that as the spring keeps them very rigid and taught. I'm still using these fenders on my bike. I've since extended them by tacking another chunk of fender onto them with and urethane glue rivets. Fully functional if not the nicest things out there.

Cathy's maple fenders set for finish and hardware.
This past year I decided to go all in on the wooden fender building process. As such, I researched and then built a steam chamber and bought a steam generator. This in and of itself was a fun little project. Along these lines I also built a new bending/drying mold. This time I used an old 26" DH MTB rim that was wider and screwed on wider spacers that would hold two sets of bent fenders. I also built the jig suck that it had slots to hold the fenders in place, negating the need for clamps.

Finally this winter I put the system to use with some wooden blanks that my brother cut for me from ash and maple. I'd not tried maple before but was optimistic to give it a try. The system worked well and made bending a breeze. I did have some trouble getting the wood up to optimal bending temp, just above 200 degrees, but the wood still bent just fine. In the future I am going to insulate my steam chamber with heating/cooling duct insulation. That should help get the temperature up some.

Finished quick mount maple fenders.
For the hardware of the new fenders, which I made for Cathy's Cannondale SuperX disc cyclocross bike, I used Planet Bike SpeedEZ hardware. This is readily available direct from the vendor and is good quality product. It isn't overly inexpensive though as a set (enough for one pair of fenders) will run you $24. Beyond the fenders, I also built the mounts to which the struts bolt via an eyelet bolt. I simply used 1" x 1/16" aluminum which I got at the hardware store. It is lightweight, easy to work with and readily available. Unfortunately, with the cost of raw materials these days, even a small 4' section of the aluminum costs about $8. That is enough for about two pairs of fenders if the mounts are not super long, which means you get about $30 in materials alone, assuming the wood was free, which it usually isn't. If you bought a 1" x 2" piece of maple it would probably run another $10 for an 8' length. Cutting that down on the table saw would probably only get you two strips, enough for six fenders.

Mounted on a bike not designed for fenders.
The new set took a little bit of fiddling to get onto the disc equipped bike but not that much. They sat securely and worked really well. For these I used an old reflector bracket I had and made a clamp mount for the seat tube, which helped hold the rear really secure. The maple is my favorite by far out of the oak, ash and maple that I have worked with. I think using redwood, mahogany or cedar would be neat as well given that they are naturally resistant to moisture damage. I may try some poplar also as it is cheap and light with an open grain that should take finish nicely.

Custom fenders.

This week I got a call from Chris at the bike shop. He had a really high end Cannondale Synapse for a customer that he couldn't get fenders to mount onto correctly. He asked if I could put a set together for him, in a day. Luckily I had a set of blanks all bent and ready to go. After a trip to his house yesterday (his day off) to get custom measurements and fitting off the bike, which he was working on on his day off at home, I returned home to start work. I got the fenders roughed then sanded and put some stain on them.

Because time was short, I went with a natural tungoil finish on them. I'd wanted to try an epoxy finish but wasn't sure it would cure over night. Of course, the test batch I did cured overnight just fine but I couldn't run the risk. While the fenders were drying I picked up so more aluminum to finish the mounts. I left them really long and wide so as to clear the rims with room to spare. Last night I riveted the mounts on and robbed the struts off from Cathy's new fenders (sorry) and finished the new ones up.

Installed on the Synapse.
This morning I went over to the shop and fit them onto the bike, a long process made longer by protecting the bike's finish with tape. This was a pretty (very) expensive bike so everyone wanted to be extra careful and make sure every detail was just right. That translated to a couple hours on top of a number of hours that had already gone into the built.

There is a reason custom anything doesn't come cheap when you start adding time involved into the equation. It was a fun project though that helped the shop out, a shop that has done a ton to help me out, and hopefully the bike's owner will like them. The fit is pretty solid and I think they look pretty sharp. I wasn't certain how the ultra modern Shimano DuraAce Di2 electronic shifting equipped bike which also has full hydraulic disc brakes and big Enve carbon fiber clincher rims would look. Given the sort of retro race bike paint scheme and somewhat otherwise blacked out feel, I think they work really well. Makes me think of a 50's era woody that had been hot rodded. The fenders also run pretty low which gives the impression that the rig has been lowered.

I know, I'm biased but I think they look pretty darn cool. Guess I'd best go order some new hardware to replace Cathy's so she has fenders on her bike. She heard no end of it being the only one on the team ride last night without.


Hill Junkie said...

MKR Fenders... I see a Kickstarter venture in your future. Good stuff.

Brendan said...

I bought some of those bamboo ones once off of ebay and they lasted about a season before a wayward stick took them out. It was the rear one and it interestingly snapped between the two struts. Is maple beefy for going into the woods?

I've had good luck with the strutless PDW ones, because there's nothing for debris to get caught on. The downside is that they're not full coverage.