Soft Jaws...they're not just for pudding anymore

Though the process of creating a custom bicycle varies from customer to customer, the basic components are the same, allowing the use of dedicated tooling to be created.  Often this tooling is designed with a range of variability so that minor changes in design can be accommodated.

Production work, however, necessitates that dedicated, fixed position equipment be used to ensure accurate, repeatable results from piece to piece.

Today, I want to talk about the importance of "soft jaws".  Soft jaws are replaceable tooling that hold a part for machining, often not heat treated, allowing the operator two distinct advantages; the ability to shape the jaws to perfectly fit the piece being machined.  Secondly, the shaped clamping surface provides greater surface contact allowing for a less robust clamping surface, leaving no impressions on the finished part.

The example we are going to look at here is a set of jaws that were shaped to accept the spider interface for the Hot Rod cranks.  In this case, the part is water jet cut to the rough dimensions and the center hole needs to be opened up to 24.02 mm and then face relieved a skoosh so that it is a tight slip fit over the bottom bracket spindle.

The base part, before machining

To place this part into a standard set of pointed hard jaws in a lathe makes concentricity difficult to attain part to part, as there is minimal surface contact between the jaws and the part to be machined.  I used a tool post grinder, mounted to the cross slide, to create a shaped opening in the face of the jaws, allowing me to have a surface that holds the part perfectly flat and concentric to the spindle for machining.

The lathe jaws, ground to accept the part

This shaping of the jaws permits a consistent origin point from which to begin the machining process, and contacts a majority of the outer surface leaving no clamping impression, therefore meeting our goals.

The part clamped and machined in the soft jaw

Whether in a vice, lathe, or in a fixture, precision soft jaws created for the operation are an asset to the fabricator and should be considered for any production piece.

cheers,

rody

Setting standards...

Forums are places where folks of like minds can gather to enthusiastically share their interests, hobbies, and professions.  The ironic twist with the niche of frame builders is that our numbers are so small, often pros, hobbyists, and lurkers share the same space.  Professionals who desire to mentor, share, and encourage others to begin the journey to mastery, struggle with how to set standards for acceptable practices.  Keeping "the bar raised" on what is to be considered the standard for quality is no easy task.

The issue with the internet, is that misinformation spreads like wildfire.  "Experts" are born behind a keyboard and within a short time, are establishing  facts that are anything but, only to have others pass it on.  The crux is when an experienced pro who knows better attempts to correct the misinformation, only to be barraged with negativity.  Soon, the experienced mentors retreat to their shops, frustrated and unwilling to make the effort again.  This is how the loss of knowledge begins in today's classroom of zeros and ones.

Enough time has transpired through many list serves/forums/pages that it has become clear to me that one can never remove the human element of ego and need for affirmation from discourse, regardless of the subject. Moderation can provide some constraint, but will never re-direct those who refuse to acknowledge or conform, regardless of the experience or knowledge possessed by those offering assistance. 

The best way to "keep the bar high" and provide the level of mentoring we wish to convey is to be the one on the field keeping the bar in place, setting the professional example. It takes time to be a presence, guide, mentor via the interwebs, and each of us must decide if that is within themselves to share and provide at the cost of time, frustration, and little thanks. 

A unified presence/effort by those that want to make a difference and see standards set is the tool to get this job done.

I'll continue to add my voice where appropriate and hope for a chorus and not an echo.

rody

Removing a broken stud...

Picked up a new to me Diacro bender that had a stud broken off in the fixturing portion of the table.  Here's a quick video showing one method of removing it so that the table will be fully functional again....

cheers,

rody

One of these is not like the other...

You've likely heard the instant ripples coming across the internet; yes, there is another bottom bracket spec coming down the line.  This time, however, it is not driven by a big corporation wishing to redevelop a standard to sell more of their branded components, it's origins lie among a small frame builder, a family owned component company, and the man who has been responsible for the explosion in frame building today by developing more high quality fiddly bits and offering them for sale, than any other.

It began one year ago, at the Philly Expo, when a conversation between a customer and a builder blossomed into a discussion on what needed to improve upon the bicycle as we know it. At the crux of the conversation, the inadequacy of most frame builders to accurately create a high tolerance, well machined interface for the press fit 30 bearings, and therefore, the erosion of consumer confidence in the standard.

Once you've been in this industry long enough, you begin to see "trends" come around a time or two.  The complaints about the press fit 30 bottom bracket ring through the air; the bearings must be pressed in with a special tool, after use they can creak and make noise, bearings fail more rapidly, they are hard for consumers to work on, etc...  Anyone remember Klien, Fat Chance, and a few others?  Pressed in bearings that gave people fits and subsequently went back to threaded interfaces...here we go again.

Let me introduce the T47 bottom bracket; a piece that begins with the same inner diameter as the press fit 30 and then adds threads.  Isn't this just a bigger standard English bottom bracket?  Nope, let me explain why...

The T47 has the following positive attributes:

- uses a larger shell to allow oversized diameter tubing to match without swaging
- the shell is thick enough to allow welding of both steel and titanium without distortion
- the threads are properly sized to facilitate hand tapping post fabrication and for maintenance
- the bb shell will allow cups to fit all current crank spindle sizes
- existing frames with press fit 30 metallic shells can now be reamed and tapped with threads, prolonging their lifespans of use
- at least three bottom bracket manufacturers are already producing parts for this spec, so parts will be available

The T47 has the following negatives characteristics:

- weighs slightly more than a standard English bottom bracket shell of the same width
- builders will have to purchase new taps and make tooling accommodations
- people who like to grumble have another opportunity to do so

I've been fortunate to have known of this for quite some time and I'm in favor of it.  I like the fact that if I include it in a build, it allows the customer to have options in the future.  I like the fact that it will save some frames already equipped with noisy pf30 shells.  I like the fact that a certain headset maker whose product I love will be making their first bottom bracket to match this spec.  I like the fact that I have a shell in my hand to build one of the first bikes...off to the shop to start making plans.

What does it mean to race?

“So are you riding in Dr. Knob’s Malevolent Team Challenge on October 10th?”

It’s a question I’ve asked a lot of folks as the date draws near.  Some respond with an enthusiastic “YES, can’t wait!”, but many give me an automatic response… “No, I’m not a racer, I just enjoy riding for fun.”

That’s disappointing, let me share why.

Whether the trails you enjoy riding are privately held or on public land, the monetary burden of maintaining these trails often falls to local volunteer groups who have embraced the effort of maintaining and improving the trail systems to the benefit of all.  Though their time is given freely, tools, materials, insurance, and requisite permits/fees are not.  That money has to come from somewhere.  With government budgets under the scrutiny of the public eye, that money must often be generated by private groups who care enough to see the trails thrive. 

Here in Ohio, revenue is commonly the result of participation in our local races.  331 Racing and the OMBC both host races on private/public trail systems with proceeds from the race fees returning to the venues to be used by the local advocates.  Your race dollars are going back into the trails you are gliding across, administered by the folks who care the most about them. 

In the case of Vulture’s Knob, we toe a very tight financial line.  Unlike public lands that have the ability to include rider liability into their overall insurance policies, funded by a large tax base, this property must stand alone and pay for its participants each season.  We generate income through two primary revenue streams; donations and race participation.  Donations yield about $1500.00 a year, leaving a gap of approximately $8500.00 annually to cover insurance, utilities, maintenance, and any improvements we wish to make to the trail system.  That’s no small potatoes.

I implore you, re-define your perspective on what it means to participate in your local races. 

Some race to set performance goals, push physical limits, and compete; it’s about going fast and we welcome that.

There is, however, another relevant perspective; racing is an element of community participation and support.  It’s part of a movement to support your trail systems, creating a sense of advocacy, ownership, and contribution to a larger goal.  Race participants are the financial backbone of many of our trails, creating recreational opportunities for all to enjoy, from cradle to grave.  Regardless of whether you stand upon the podium or just finish with a smile, race participants are stewards of our trails. 

For us, it’s about giving back to something you believe in.  Vulture’s Knob allows us to share our love of mountain biking with others in a way that is unique, special, and is held tightly in our hearts.

“So are you riding in Dr. Knob’s Malevolent Team Challenge on October 10th?”

I hope you will join us?

Broken seatpost removal...

Have not had anything too informative that has not been covered in this blog in the past, but had Paul's Space Bike come in with a broken seatpost, the end stuck fast in the frame.  That makes riding difficult if not down right uncomfortable.

You need two distinct forces to remove a stuck stub of post; mechanical and temperature.

I've never met a stuck post I could not remove yet, so though I don't relish these fixes, they are strangely alluring in their challenge.

Here was a walk down memory lane for a stuck Thomson...

Stuck Thomson post...

This ti post gave up the fight pretty easy though.

First thing I did was look to gaining some mechanical force.  Trying to grab the stub with a pipe wrench or other "crimping" style tool will only ovalize the tube and create pressure on the inside of the seat tube, increasing the difficulty of removal.  So I drilled a through hole in the remaining material that allowed the passage of a 5mm allen tool that I would then use as a lever to turn and lift with.

Next, I applied heat to the inside of the post in it's full diameter; enough to create some expansion of the seat tube and loosen the potential corrosion, but not enough to affect the paint.

Then it was a simple twist and pull with a few choice words when I cut my finger on the ragged edge of the broken post.

Wah-lah...

Inspection of the post showed that there was a distinct discoloration inside the wall of the tube about 1/8" long, possibly a defect during the drawing of the material.  Who knows, just glad that Paul is Okie Dokie and that the bike will now be on the trail again soon.

cheers,

rody