[Smudgemo]

I got the idea to build a sizing board from Neil (mod of The Frame Forum) and Doug Fattic awhile back because I felt it would offer a great combination of accuracy in an inexpensive fixture. Based on internet advice, I came up with the plan for this one as something somewhere between the simplicity of Neil's, and the hugely complex design of Doug's. I'd post Neil's pdf, but I'm not sure if that would be cool. Doug's can be seen on the FF if you search for my thread on sizing boards.

I figured out the dimensions with SketchUp, and built it mostly out of 6061 aluminum and MDF. I imagine the materials only cost around $50 or so. It takes some measuring and angle-checking to get set up, but I think it's going to work for me for now. I'm currently not able to set both chain stays in it, but I've copied another Doug Fattic tool for that, and it'll probably be a near-future S&TF entry.

In this photo I've got it set up for a fillet-brazed mountain bike that just happens to be in my preferred size. The miters are done, and the tubes need to be prepped for joining. I'm planning to include a set of posts for cantis because I've got this excellent set of non-disc King/DT Swiss/Mavic wheels that have been hanging around the attic for a few years, and I'm hopeful I'll be able to find a lightly used 100mm fork with posts somewhere.

I'd like to give a shout out to Doug and Neil for the inspiration and information to throw this thing together. I didn't use a fixture for my first frame, but it's feels really cool to having built a fixture that should be very useful. It's slow to setup, but not difficult.

This is my second frame, and I'm hoping to get the front triangle brazed up this weekend. While I'm at it, another shout out to zipzit for building the tube notcher program now hosted by Nova. It's sweet, and looks like it'll be extra helpful to cut the seat stays properly. The measurement to the center of the uncut tube was very helpful for lugless building.

Perhaps this is merely a Friday high and a Lost Coast Brewery 8Ball Stout talking, but bikes are really cool. I'm glad I sold my jet skis ten years ago and started riding.

-Ryan

 

[Thylacine]

I think I like the Aluminium extrusion designs better. MDF is horribly unstable.

 

[doug fattic]

Ryan,

Congratulations on your fixture. It should work great just as it is. In time - if you have the ambition - you can add some bells and whistles. If you wanted, you can stabilize its squarness (if it is not on the board) by placing another support piece diagonally between 2 of the other pieces that make up the outside rectangle.

It is also fairly easy to mark seat tube angles on the fixture so you don't have to use a protractor to do it. Another little feature very easy to add is a carriage bolt on the bottom support piece to the left of the head tube piece (that represents your wheel base line) to represent the center of your front wheel (You might already have one there). The advantage of this is that you can now measure from that point to where the bottom of your head tube should be very accurately. Just remember that you measure the rake at a right angle to the head tube piece and not along the bottom support piece.

I use carriage bolts to hold the pieces together. Those are bolts that have a square shoulder so they won't turn in a slot. I wasn't sure if that was obvious enough in my pictures.

I have found flat stock to work better for me than aluminum extrusion like 80/20. I've got massive cast iron surface plates (and an aluminum one too) but I understand that 2 pieces of MDF board glued together make a fairly decent and flat support. They are great for budget frame equipment.

One of the features that I really like with this type of fixture is that I can check the accuracy of my miters and if necessary alter the miters so that they are the same as the original design. Some fixtures require the miters to set the fixture which can result in some design variation.

Pictures of my fixture are here: <www.ukrainebicycletours.com> Anyway nice work and I think you will find it is easier to use your fixture to design a frame than do a full scale drawing.

Doug

 

[Smudgemo]

This is a photo during the build that better shows the individual parts. The backer is actually particleboard, not MDF. It's two 3/4" layers glued together and sealed with polyurethane. Moisture could very well be an issue, but a quick google search suggests it won't be problematic. Plus the humidity here is very low for most of the year. I might ditch the board at some point and add corners and braces to lighten things up and hold it together, but I wanted to be up and running before the next time I've got machine shop access.

The rear axle is 10mm drill rod tapped for a 1/4 20 bolt, so dropouts fit perfectly. Since it's only for reference, the front axle marker is simply a 1/4 20 threaded rod, nut and wingnut. Everything adjusts fairly easily, and I am indeed using carriage bolts.

Thanks for mentioning how to measure rake, Doug. I either forgot or didn't realize that part, so I'll have to recheck my measurements before I start joining the tubes.

 

[doug fattic]

Ryan,

A couple of questions. Did you recess the underside of the top and bottom supporting aluminum strips or the particle board to make room for the head of the carriage bolts? Did you buy the cones or make them yourself?

Thanks,
Doug

 

[Smudgemo]

I did route the areas below the slots. I you look closely at either photo, you can see I just free-handed it instead of clamping a fence to the sheet. I also made the cones myself, but I wasn't careful to follow any set plan. It seemed a longer one would be better utilized at the bottom of the HT.

Feel free to offer any suggestions/criticisms.

 

[doug fattic]

Ryan, I think the way you've made your fixture (Neil isn't here so we can call it by its American name) has the greatest cost to performance ratio. In other words you got the best result compared to how much it cost and the difficulty of putting it together. I think many just starting out should look at your design as a model of what they can do if they are on a tight budget. Features to make it more convenient can be added if and when there is a desire.

If someone doesn't have access to a milling machine to make the slots in the flat pieces, it is possible to create them by bolting or brazing 2 pieces of slimmer flat stock together. For example, if the top and bottom support pieces are 1" wide and the middle slot is 1/4", it is possible to create the same thing using 3/8" wide flat stock with short pieces of 1" flat stock (with a tapped hole in the middle) underneath so everything can be bolted together with 1/4" (or M6) screws into one piece. If someone wanted to braze them together it could be done with 1/4" thick cold rolled steel with 1/8" X 1" cross strips holding them together.

I've seen a lot of ingenuity in home made fixtures and have thought about their design a lot. When I turn my framebuilding class notes into a how-to-make-frames manual, I know readers won't have my Anvil or Bike Machinery fixtures to build with. Neither will some be able to afford the fixtures I have laser cut and etched out of stainless steel that you partly based your design from. What they can do is make something similar to what you have done. We are all different and approach problems like fixture making in different ways but I think yours should receive top consideration from new hobby builders.

Doug

 

[golden boy]

Thanks for sharing your design, Smudgemo. It's a nice endorsement to have someone like Doug Fattic offer his praise. I am preparing to hobby-build my first frame and this morning I have been diving into frame fixtures. It's a bit overwhelming. I've read that one can build a first frame without using a fixture of any kind, but I can't imagine how one could produce a quality frame that way. If I'm going to do this, I want to do it right, and for me, that means using some kind of frame fixture.

 

[Smudgemo]

Thanks.
Funny story. I made that jig and then never used it. Each frame has been built using v-blocks and a BB post. At some point before I used the jig I bought BikeCAD. Having every angle and length measurement on hand seemed easier than setting up the jig and cutting each tube to fit how the jig was positioned. Now I measure the angle of the HT/DT, then the DT/ST, and then the CS/ST. The top tube and seat stays are cut to fit.

Before buying a bunch of stuff and then trying to figure out how to use it, I’d really suggest you skip a jig for now. Buy one later if you decide you hate building in subassemblies.

 

[golden boy]

Yeah, I after I posted to this thread, I came across your v-blocks and BB post.

Dang, getting started is harder than I thought! So much to think about. Thanks for encouraging me to skip the jig for now. I think it is proving to be a distraction. I may start by just designing the frame using CAD, maybe BikeCAD. At least that's something I already have a level of comfort with. I've done CAD at a previous job, including 3D stuff using Pro/ENGINEER. BikeCAD or similar ought to be a piece of cake by comparison.

 

[padelsbach]

Sorry for resurrecting this thread, but I'm wondering if one actually tacks/brazes in the fixture. How far off the board is the joint/tubing? Seems like the board could burn if it was too close.

Thanks and nice work!