Last minute opening for July 22nd frame class

26 06 2013

There has been an cancellation for my July 22nd class only a month away.   This is your chance to circumvent the 6 month queue and get to making some bikes.   Check out my website to secure your spot htttp://www.framebuildingschool.com

Thanks everyone!

Dave Bohm





You really don’t need a fancy jig…really!

9 05 2013

What I speak of a generally called a frame fixture or jig.   An apparatus that holds all the frame tubes in the right proximity to one another to allow one to weld/braze a bicycle frame.   Believe it or not a most excellent job can be done without one or with minimal fixturing.

Yes, I have one.   Actually I have three.   What does it do for the professional?  It makes us much faster while still being accurate.   Time is money and in addition to that I am fully capable of screwing up at a moments notice.  I have literally looked at a number and convinced myself it says something else so fixtures remove the possibility of making gross errors.   It is much easier to look at the seat angle of my Anvil fixture and when the hash mark lines up with 73 degrees, its 73 degrees.   Yes it’s a beautiful thing and I highly recommend the fixturing from any of the great suppliers.

I want to say this.  If a fixture is not easily set up and accurate when set up I rather not even have it.   Yes, I would rather build with a simple surface plate than have a fixture with a headache of a setup, is slow to setup and only opens me up to mistakes.   So it’s either a well made fixture, professional solution  or table.

Most students have the fixture/jig and numero uno priority when they get home.  I press very hard that so much comes before this.   Of course the basic hand tools, work bench, vise, torches but the next thing on my list is a flat surface of some sort.   You cannot (yes I said it) you cannot do good accurate work with only a frame jig.  You must have some way of confirming your work and therefore the surface plate is central to the whole process.   Does it have to be a big heavy thing?  not one bit.   We are not looking for aerospace tolerances here.  Many solutions will do.

Wait, there is more!   Do you know you can use your table as a fixturing device as well.   With some very simple hardware, much of it bought from tooling suppliers for very little money you can build accurately and quickly.  One of my former students just did such a thing and I am very proud of what he has done.   Pictures to follow.   The concept is simple.  It was relatively inexpensive and allows for great variations in design.  Also it allows for the requisite checks necessary to ensure a well aligned bicycle frame.

post3 Jig 3 Jig 2 post1

post6





Partial scholarship for framebuilding course in July

2 04 2013

$1,500 Framebuilding Scholarship

How:

Create a public social media campaign (YouTube videos/blogs/Tumblr page/whatever) to convince me why you deserve this scholarship. Judging is based on your creativity so have fun with it. Women and people from continents I have not taught from (Central and South American, Africa, Middle East, Far East) are highly encouraged to apply.

Fine print:

  • This scholarship is for the 07/08 to 07/20- 2013 class only.
  • Deadline for submission is May 15th 2013
  • The scholarship only covers half of the tuition. The winner still needs to pay the other half of the tuition, along with room, food, and transportation.
  • Scholarship winner must pay the $500 deposit at the time of scholarship acceptance.
  • Half of the remaining balance ($500) is due 2 months prior to the class start date.




Disk brakes on classic road frames a big no, no….

27 11 2012

Certain items just don’t work with classic diameter steel very well.

A prime example of this is disk brakes for road, road race or cyclocross use.   I look forward to the day we have great hydraulic disk brakes for road bikes but in the mean time there are maybe more disadvantages than advantages.

Steel road fork design currently dates back at least 60 years and they were not engineered with disks in mind.   If you visualize a traditional caliper or cantilever brake you can see that the braking forces are equal on each side and that they are closest to the strongest portion of the fork (the crown)  Disk work differently.    The braking forces are on one side only.   The force is as far away from the crown as possible creating a large leverage ratio.  The forces are also typically pushing straight towards the rear of the frame as well.   In the worst scenarios this can cause the fork to twist permanently and essentially it is damaged beyond repair.

In order to alleviate this one would have to use fork blades that are much thicker and therefore heavier, stronger crowns and disk brake mounts.  This is next to impossible with traditional forks that have a brazed crown.   It is possible with unicrown steel forks but there is a weight penalty as well and it does not fit the aesthetic of a traditional lugged frame.   Even carbon forks optimized for disks tend to carry a fairly hefty weight increase for the needed strength, around 150 grams.  Many of these new carbon forks are of the newer taper standard and this requires a huge head tube on a steel frame which is once again heavy as hell (at least a 100grm penalty) and no lugs are made to fit them which means by default you are welding or fillet brazing a frame.

Now onto the disk brake.  The only one that currently works well for road/cyclocross  is the Avid BB7 and although admirable it has its issues.   Disk rub and squeal for one.  Weighs a lot itself, add in the beefed up fork and downtube and it weighs more.   They interfere with rack placement and fender attachment as well.   The only thing I think one could really claim as being superior is alleviated rim wear but good ceramic coated braking surfaces will last at least 3 years under the hardest of use and honestly don’t cost a lot more than a new disk so I consider it standard wear items.   Maybe someday we will have much better options but heavy, noisy, and mounting difficulties make them not the best choice in my book for Randonneur or cyclocross bicycles.

Now, you may ask, “Hey Dave,  I have seen students who had disk brakes on their builds at your shop.”  Yes, that is the case but you may also notice that the build method was different.   I will do this but typically the frame must be fillet brazed to take advantage of the tubing that can handle this sort of thing.  The frame will weigh more.  Usually I suggest using nice Paragon drop outs for the rear which incorporate a disk mount and they cost more and are more difficult by far to work with.

You may also say, “Hey Dave, my Google-fu shows me that lots of other builders have done just such a thing.”   Well,  I am open to many different concepts with framebuilding and many ideas are great ideas.   Although in my opinion most of these builders doing this are just plain wrong.   Many do not have the technical expertise to make a reasoned decision on this.    Second, most of these bicycles are city bikes and the like which really will not experience high loading factors over the units life, like a mountain bike or a road race/touring bike.  It is very different if you really plan to use it to a high degree.  This singular choice pretty much dictates the design and construction methodology of the entire frame/fork so please keep these issues in mind when deciding to use a disk or a traditional brake.





Trust your builder!

13 10 2012

This will serve as one of my eventual list of canned responses.   I get a lot of various types of e-mails.

This one is a classic.   The “I hired another framebuilder and I am doing research into how, when, where, why for them.”

Examples of this are everything from where did you get your tubing to what are your exact design specs.   Most of the questions border on flat out asking for proprietary design elements but really what is the more annoying thing is this.

You (the client who is contacting someone other than their primary builder) has hired a professional to service you and that you should let them do it.   Either this comes from two places.

First and probably least likely is that the framebuilder really doesn’t know where to get said product or how to design/build the product and that alone should be a warning to the perspective client.

More likely though is that the client is not allowing the framebuilder to actually do their job and that is provide the contracted services to the client.   Maybe its that the client is trying to run over the framebuilder? or maybe the framebuilder is trying to put off the client and the client isn’t getting the point?  Could it be the client is trying to have made a product that is out of the scope of the builder or more likely trying to get a less experienced builder to make something that is made by the specialists for much more?   One can only guess.

Dear Client of another framebuilder.   Trust your framebuilder!  You have paid them for a service, let them provide that service.   If they cannot provide that service then seek out someone that can.   If you are just being anal, backoff.    At the very least have your framebuilder contact me directly.  I will be much more open to answering professional peer questions than I am a random persons e-mail.

Oh and by the way.  Inevitably these e-mails are practically a demand for information.  A couple of “pleases and thank-you’s” would go a long way.





Takin’ it to a whole nother level…..

2 08 2012

Got to toot my own horn here for a moment.  I recently finished a paint job on a student frame from a few months back.   This student stayed for a month and built two frames taking both the 101 and 202 courses back to back.  This is his second frame and incorporates more advanced techniques like lug cutting and producing your own lugs through a process called bi-lamination.  He did almost all of this himself.  The lug decorations were 100% him.  I only guided on the next steps following the production of the first frame.

I am throwing down the gauntlet on this one.

the gauntlet

If you are looking for a bicycle frame building school and you can find one that has empowered students to produced  results  ANYTHING like this then I wholeheartedly suggest you go there.

Around here at Bohemian….who know, we take it to a whole nother level…..





Some Lug hotness on a Tuesday

4 10 2011

Lest you think that because I am totally lame and almost never update my stuff (blog, facebook or websites) here are some goodies I have been working on.

and a sneak preview of retardedniculousness coming out the shop…








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