Have a look at the original Plycycle here .

29 April 2013

Making the rear stays work...

On the first Plycycle the bottom rear stays came together with relative ease, it has become apparent that this was for several reasons. First, I didnt know it could be a problem area, but mostly because I had chosen to build the frame around 700c wheels with racing tyres which are very thin. I was also lucky in that the chain set I chose was a design with a large gap between the crank arms. Both of these factors allowed me to make the bottm rear stays straight and strong with no need for fancy shapes to get clearance.
However on the Plycycle Mk2, I have decided to use 26 inch wheels with slick tyres. These are essentially mountain bike wheels which are wider, even with the slicks on they are nearly twice as wide. Added to that the chain set i had planned on using (the Simano Alfine) has a relatively narrow clearance between the crank arms. I think I will have to look into an alternative crankset as I will need all the space I can get.
This drawing shows the problem, in order to make the new rear stays I am going to have to make the bottom rear stay a fairly complex shape. I may even have to set the wheel futhur back to make the space I need. I have already toyed with the idea of moving the botton bracket forward by an inch to help make more space, but this may compromise the cycling position.
I started to try and plan it out with some card board, and as things stand I would need a shape similar to the drawing above.
This is about as fat as I can get the bottom rear stay,
the fatter the better as it is a point of high stress in the frame.

From the side the geometry looks like it will all work out fine.

I like scribbling notes amd measurements down on bits of wood.

 I think the best way forward is to get the chainset, then work to that, otherwise it will all be a guessing game.

21 April 2013

Frame shaping continues.

This was a trimming and tweaking session. Earlier in the week I had spent some time looking at the frame, trying to work out what should stay and what should go from the initial (rather generous) frame cut. I marked out my thoughts with pencil and today I started trimming.
In some places I took off about 6mm, and in others it was just enough to get all four layers to match exactly.
There was lots to do with the jig saw, and I used an angle grinder with a car paint stripping disc to do some edge rounding. But both of those tools while quick are a bit heavy handed. They leave little bumps and irregularities that are best fixed with hand tools. I started a bit if hand tool work, but that will mostly start in ernest in the next session. So the power tools are quick but it is vital to remember to leave a little extra to alow for the refining with the hand tools, which does inevitably take more off the frame.


It is good to see the shape coming together now. I am always guessing how much to take off, as once gone it can't go back. I want this bike to be lighter, but it also needs to be strong enough. The first plycycle was strong, but a touch on the heavy side, so I am trying to improve on it. Only time will tell.


This clip shows what I have described above in more detail.

12 April 2013

Digital design.

I had a go at knocking up the old Plycycle in Google sketch up, with a view to useing it as a tool to push the design of Mk2 in the digital world, but to be honest I was fighting a loosing battle.
I think that the best way forward is as with the first project, just get into the garage and make the thing.
In the past, I have often had the oppotunity to learn computer animation, but it just never sat very well with me and I have always felt more at home working in the physical stop motion world, where things are made and you can touch them. I do like the digital design world, and I do use it alot, but with other people driving the computers. I think I will leave it that way for a bit longer.

Any way here is a little animation of what I did build in Sketchup.
So I failed to move the design on digitaly, but I did have more sucsess (as seen in the last post) with a sheet of card board.

7 April 2013

Cutting the main frame shapes.

Just getting on with it is often the main problem on a project like this, so I grabbed the opportunity to get started today.

I adapted the frame shape using the original cardboard template from Plycycle, I added extra around the bottom bracket area, and I am going to try a wooden seat post structure this time too. So with those additions I cut out four shapes from the template.

Last time I used dowel to hold the elements together, but this time I have used some bolts, the dowel was tricky to get out of the finished frame without damaging it last time.

That was a solid two hours work, including the thinking, prep and cutting of the main frame elements from the template.

The cardboard template on the fresh sheet of plywood, ready to be cut.

The four frame elements all bolted together.

It feels great to get it started!

6 April 2013

A fresh sheet of ply.

I made the first move in building the Plycycle MK2. I bought a fresh sheet of plywood. I made the trip to Avon Plywood, who are the main retailer of ply near Bristol. They store it flat and have a huge choice. This time I went for 9mm long grain birch ply. The first Plycycle was made from 12mm birch, and this worked very well, but having looked it over and ridden it a lot now, I think 9mm birch ply will be strong enough and be lighter into the bargain.

The Avon Ply warehouse, they got alot of ply.

I think it is great that a sheet of wood can become a bike.

4 April 2013

The original Plycycle.

The first wooden framed bicycle I made was the Plycycle. There is a website showing the finished bike at www.plycycle.co.uk there you will also find a link to the blog of the build.

3 April 2013

The Plycycle Mk2 starts here....

Ok, so this is only the blog, but this is where i will track the build of my second wooden framed bicycle, the plycycle Mk2.