The Bike – Part 4: The Seven Factory Tour

Let me just say right up front that I love factory tours. In elementary school we toured the local Stroehman’s bread factory (the smell was heavenly), where we saw a worker use a large shovel to scoop back into the carts big piles of dough that had fallen on the floor.  In the fourth grade, I got a personal tour of the Avco airplane engine factory in Williamsport as part of a science project.  In my junior and senior years of college, my major (ceramic science) had a required, 1 credit, one week field trip in late August, just before school started.  We visited steel mills, glass and dishware factories, brick makers, and so on. It was incredibly interesting!

All that said, seeing my actual bike getting made at the Seven Cycles factory in Watertown, MA, this past week was special.

Seven entrance

The entrance to the factory was hard to find, an unassuming doorway tucked behind a car dealership.  Entering the door on the left in the photo, I stepped around workers doing construction in the garage bay, then went through a door marked Main Office, into a good sized room w/ a counter and desks behind.  A guy from one of the desks greeted me.  I told him I was a bit early for my 11:00 tour.  No problem. He asked me to sign the guest book, which was clearly geared for guests there for tours, then ushered me into a larger room where I would wait for the next person.

And what a fascinating waiting room it was!  About twenty feet square with high ceilings (it was a really old industrial building that had been refurbished), with a wide variety of Seven bikes on display – road bikes, mountain bikes, all sorts of bikes, mostly titanium (Ti) or carbon fiber/Ti composites.  One corner of the room was set up with rows of folding chairs and a small lectern.  There was a leather sofa and, best of all, there was a coffee table laid out with some tubes and manufactured bike parts.

The tubes in the photo on the left are all the same size but different materials and construction techniques.  The difference in weight was obvious in the heft.  From the left, from heaviest to lightest, is double butted steel, straight wall Ti, double butted Ti, and carbon fiber.

The pieces in the right photo include a Seven nameplate, rear dropouts, a seat stay crosspiece, and sample welds.  The workmanship was impeccable, a pleasure to touch.

Shortly, a fellow named Matt appeared, to take me on the tour.  We chatted a bit about my riding experience and plans, he gave me a pair of safety glasses to put on, then we went through a set of double wooden doors onto the factory floor.

In front of us were some racks holding a selection of shiny titanium tubes 10 or 15 feet long.  Next to that was the machine shop, pictured below, with a variety of lathes and milling machines.

Seven-machine shop

Each machine is set up for a particular part of the frame.  That way, they don’t have to spend a lot of time on setup – just tweak a bit for the specific design at hand.

In the photo above on the left, you can see a set of chain stays jigged so that the cutting tool cuts both tubes at the same time with precisely matching cuts.  ( The cutter looked a lot like a normal hole saw you would buy at the hardware store.  Matt said that is basically what it was.  They used to use special, expensive cutters, which needed frequent sharpening.  Now they just buy cheap cutters and discard them frequently.) The photos on the right are closeups of a horizontal milling machine and a lathe.  Matt said all these machines were bought used and they all look really old, but he says they last forever and can be repaired.

One person machines all the parts for a single frame, and at the conclusion of all the machining, signs a paper traveler that moves along with the bike.  He or she (I saw at least a few women workers) selects stock from the rack, cuts pieces to length, then moves from machine to machine to produce all the pieces, all based on the design and dimensions called out in the design in the traveler.  It is most definitely not a case where a person makes a bunch of  the same piece, one after the other.  It takes about a day for a machinist to cut and machine all the tubes for a typical bike, although Matt later pointed out a carbon fiber/Ti frame with an incredible amount of intricate machining that he said took 5 days.

After the pieces are machined, they are cleaned inside and out with a solvent.  Then they go to the welding shop.  There the frame pieces are held in precise alignment in a hydraulic jig, shown below with a frame held in place.  The really important thing is to hold the head tube, the bottom bracket, and the seat tube all in exactly the correct relationship to each other.

Seven-welding jig loaded

When everything is lined up, a person tack welds each piece to the next.  This holds everything together so the frame can be removed from the jig for final welding.  Then all the major joints are welded.  Next all the detail welding is done, such as adding cable guides, fender mounts, water bottle mounts, etc.  All the welding is done by hand, using TIG welders, with the inert gas piped in to each workstation.

There were two newbies there learning to weld.  Matt told me they had been hired about a month ago, both with welding experience.  They weld practice joints all day.  That is all they do.  He said they should be ready to weld real frames by the spring.

Next the frame goes to the finish machine area.  There they double check all the alignments.  I think this is also where they install the rear dropouts, although that may have been done in the main welding area.

One thing they do here for sure is to prepare the top of the seat tube. There is a lot to that.

As I’m sure you know, the seat post (which holds up the seat) slides inside the top of the seat tube.  A clamp around the top of the seat tube holds the seat post in place.  The top of the seat tube has a small slit cut into it, so the clamp will have something to compress.  And as Matt pointed out, if there is a slit, there has to be a small hole drilled at the end of the slit to avoid stress cracking.  And so there is.  (It turns out that 4 of the 5 metal bike frames in our house (both steel and aluminum) do indeed have that small hole drilled.  The lone exception is my aluminum Cannondale mountain bike.  However, there is no stress cracking apparent.)

One common problem with all metal bikes (it has never been a problem for me with my carbon fiber bike) is that, after time, the seat post and/or the seat tube corrode a bit, and weld themselves together.  At best, you can separate them with a lot of effort.  At worst, you cannot separate them without destroying the bike.  (That is currently the case with my old steel Bianchi, the original Bill the Pony.)

This should be less of a problem for a Ti bike than for steel or aluminum, I would think, but possible none the less.  So Seven installs a carbon sleeve (not carbon fiber – the sleeve is a dense fibrous carbon) inside the top of the seat tube. The sleeve is pressed into place, then the whole frame is baked in a low temperature oven for a while to cure the bond.  Then they cut the slit and drill the relief hole.

The other big thing done in the finish machine area is CNC milling of the bottom bracket.  The bottom bracket is probably the most important part of a bike frame, in terms of alignment and precision requirements.

CNC stands for computer numerical control.  This is a large cutting machine for precisely machining components.  As the name says, it is done under computer control, so every piece should be exactly correct.  Matt told me that all this machine does for them is bottom brackets, of which they only have a dozen or so variants that cover all their bikes – road, mountain, tandem, you name it. So they mount the frame on the machine bed such that the bottom bracket is at a known point, load the proper program, close the door and press a button.  Out comes a perfectly aligned bottom bracket.

The photo on the left shows the bed of the CNC machine, which is inside an enclosure.  On the bed, the things standing up are magnetic chucks which mechanically clamp to the frame and are then held in place on the bed with strong electromagnets. It makes it really easy to securely clamp any frame in a precisely known position, so the cutting head can very precisely machine the bottom bracket threads.

The cutting head is above, near where the little red thing with the yellow tip is sticking out.  (I’m guessing that red thing is an oil squirter.) In the picture, there is no cutting tool in place.  The head moves to a carousel holding about a dozen different cutting tools and picks the tool it needs for the next operation.  The photo on the right shows the bed, the enclosure doors and the control panel.  This machine is about 30 years old, and they are beginning to worry about getting spare parts.

After all the machine finishing is complete, the frame goes to a hand finisher.  There, a worker  uses a ScotchBrite-like material to lovingly polish every square inch and every nook and cranny.  You can see, and feel, the titanium going from a dull luster to shiny, never to dim again (unlike steel).  If the frame is to remain unpainted, as the vast majority of the Ti frames are, then it is now complete, except for the application of the decals.  No clear coat necessary.

My bike is to be painted – matte canary yellow.  Here is the paint scheme.  (I hope the color looks better in real life than in this rendering.)

Bill the Pony II paint scheme

We finally caught up with my actual frame in the queue outside the paint booth.

The photo on the left shows Matt pointing to my frame, hanging in line outside the paint booth.  Each frame has its paper traveler hanging off it, with all the information about this frame.  The photo on the right is a closeup of my bottom bracket.

The paint booth is a serious affair.   It is actually two adjoining little rooms in the middle of the manufacturing space.  One room is the actual spray booth, and one is  a drying room.  There was one bike in the spray booth, and several in the drying room, all with various colors, designs, and masking still in place.  One person does all the painting, but I did not meet or see her.  She too will sign the traveler.

Matt didn’t know how many coats my bike will get, but probably 3:  one primer, one color, and a clear coat.  He also didn’t know how long that would all take.

Seven-holding my frame

[ For the record, they promised 6 to 8 week delivery from December 3.  So I am expecting the end of January. Anything sooner would be a bonus. ]

From there, my bike will go to shipping, where it will be boxed and sent to the Ride Studio Cafe in Lexington, the dealer I bought it from.  I will pick it up, caress it for a few days, then take it to the Bikeway Source in Bedford, to be built into a complete touring bicycle.

I can hardly wait!

About Dan Hurwitz

A software guy taking the time for a big ride - coast to coast.
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1 Response to The Bike – Part 4: The Seven Factory Tour

  1. sailaketch says:

    I love old factories also, I used to get paid to visit them

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