Gluing the frame part one.

There was a window of warmer weather last weekend which allowed me to do the first epoxy resin work on the frame this year. I glued the left hand quarters of the frame together.... making a half. A small but significant step.
I Mixed up the West System epoxy, 'wetted' up the two sides and then spread on the resin with microfibers for the main bond. All god so far. it was only when i cane to clamp it all together that i remembered that last time I had to borrow extra g-clamps. I had forgotten to do this so I had to improvise. I used what clamps I did have to hold the main sections and then to clamp the remaining areas I placed the frame on some wooden blocks and then used some heavy engineering bricks from my back garden to apply pressure. it wasn't quite enough so I put a tool box on top of the bricks.

Make shift clamping in action.

I am pleased to say that it worked. The bond is good. however I will be borrowing more clamps as it really is much easier that way.

Laying out the pieces.

I had a good stint on the build this weekend, and the main aim was to lay out the main pieces and see how it all looked. This was the first time all the main bits have come together and actually resemble a bicycle. Finally! It was a mile stone.

After I got over the fact that it looks like a bike, I started to take a more critical look at how it was actually shaping up. As it turned out there was a much larger gap between the rear wheel and the frame than i had anticipated. I think this was because when I first set the geometry I was going to use track style drop outs as I had on the Plycycle Mk1. But I changed to vertical drop outs, and although the geometry lines are the same, the place in which the wheel sits is set, and it is quite far back. I hadn't appreciated how much difference this would make. Not to worry though, it is a wooden frame and it is simple to shorten the stays, but this changes the angles of the rear triangle. I couldn't change the bottom stay fixing as it is surrounded by the main frame, however the top stay junction is fairly simple. So I set about the fix and an hour later it was done. See the before and after pics below.

 Before fix. Large wheel gap.

After fix. Wheel closer in.

I also notice now that the angle that I had placed the forks on is not great. They are just placed on, but along the pencil line I had thought would be best. I think that the problem is the opposite to the rear wheel. I think that the front wheel needs to come forward, away from the frame a tad. I will have to look at that properly when I have the head tube made and ready to fit.

Putting  a temp wheel in made me realize that it will be much more critical getting the rear drop outs in the correct place now that i am using vertical rather than track style. With track style there is a bit of wiggle room when bolting the wheel in as you can slide the wheel left and right a tiny bit to get a good alignment. However with the vertical drop outs the wheel is set, one position only. I think I will need to make a jig fot the final gluing.

Rear stay rough assembly.

Over the winter I have managed to get some time to tinkering done on various bits and pieces on the frame. Mostly it was tidying up details and making joins more accurate.

Rear drop outs rough assembly.

 The biggest step forward has been the shaping and fitting of the metal work to connect the rear stays to the drop outs.
I am doing it loosely at the moment to get the fitting. I will then spot bond the metal work in place with an epoxy ready for braising. I have to be sure of the fit as I don't really want to have to remake the metal parts, so it is has to work first time. This system worked well on the Plycycle Mk1 so I think it should be fine this time too.
Incidentally I bought the drop out ready made and raw tubing from Ceeway.

Making it hollow.

As I am not an engineer these stages of a build often cause me to procrastinate over the next stage. The solution has usually been just to get on with it and follow my instinct. So that is what I did for this bit, the hollowing. On Plycycle Mk1 i created a lattice of triangles along the top and down tube sections. I wanted to try something different, so I have used a simplified version of a technique that Renovo Bikes in Oregon USA use. Rather than hollowing out the whole frame section as one, the idea is to add some strength by creating a devider and making two cavities. I really hope this works as it is critical to the integrity of the frame. I am not reducing weight to make some sort of feather light bike, I just want it to be a reasonable weight, with out compromising the strength or becoming too flexible.

Here I removed the outer two layers of the frame and bolted the two center sections back together so that the holes lined up, obvious, but really vital that it all lines up when it is time to bond it all together.
Just on a technical note, I was possibly a bit hasty with my 27mm spade drill and I caused a couple of laminate layer chips in a couple of places, I will have to cut them clean and resin in some filler strips. unfortunately two of them are on the top tube section and will be very visible if not patched up well.

The two middle sections with cavities cut out.

I think I will drill additional holes once more of the finishing is done. Once I am happy with this it will be time to bond the two half's together to allow for more accurate shaping to continue.

Some lovely bits arrived.

A very strange looking parcel arrived in the shape of a blunderbuss.

However it was the Ceeway parts delivery.

Lots if lovely metal bits for the build.

The long tube is the shortest length I could buy the 22m diameter 0.9 chromoly in. I will make the sleeves to connect the wooden stays to the rear drop outs. 

So now I just need to get busy bringing it all together.

Resurrecting the build.

I had intended to make most of the frame by the end of the summer, however, real life (family, work, money) got in the way and I have had to endure seeing the project sitting idle in my garage  as I get on the Plycycle Mk1 and ride to work each day. However, I have got the wind in my sails again and work on the Plycycle Mk2 continues!

Where I left the frame was cut out with some very basic shaping and also some basic shaping of the rear stays. However they were all still separate bits.

So to move things forward i decided that I needed to see the frame come together. To do this I needed to cut out the receiving shape for the bottom stay. I had originally intended for this to be a simple 90 degree cut into the main frame, however when I came to cut it I realized that there was enough material to make a slot. So I carefully cut the slot and i think that with some shaping it will not only add a bit of extra strength, but will look really good too. this is another example of the organic nature of my design build process.

Plycycle Mk2 frame cobbled together for the first time.

Bottom stay junction.

 

rear stay wheel space.

I am pleased that all of the measurements worked out so far. The curved shapes of the rear stays seem to work out too, which is great as they were hit and miss with several attempts. I have ordered the metal pieces from Ceeway hopefully they will arrive soon and that will be a focus for the next stage.

A look at the cobbled together frame.

An extra problem is that with the onset of winter doing any resin work becomes tricky as it doesnt like the cold, it takes an age to go off. I am looking into some heated workshop options, but in reality the resin work may have to wait until the spring. 

Rear stay rough carve.

 

So having trimmed off some bulk material, it was time to do some carving. I attached a rough grit car paint grinder to my angle grinder and set to work. It worked a treat. Fast and suprisingly accurate. I wouldnt use it for anything fine, but as a tool for getting the shape fleshed out it is marvelous.

 

Rear stay sections rough positions.

 Rear stay sections.

 

 

Getting the symetry to work on this has been a challenge. The parts do not have to be identical in shape, but the points at which they meet the frame and the wheel drop outs do need to be very acurate. So the stay arms will be a little organic in shape, but the wheel will (all being well) sit true to the main frame.

 



 

Video clip of the rear stay work in progress.

Trimming.

Having bonded the 5 layers of each rear stay it was time to start the shaping process. However I needed to get rid of lots of material in some places, so instead of hacking at them with files and rasps, I set about them with a wood saw.

Cutting rear stays down to size.

 

Nesxt step is to actually do some broad stroke shaping. I am going to give the angle grinder a go fitted with a car body paint stripping grit disc. Should be interesting.

 

 

 





Rear stay bonding.

Having spent a while getting the shape of the rear stays how I needed them, and then a delay getting the epoxy, it was great to finally bond a set together.

As I mixed the epoxy up the process came flooding back to me, wetting up, micing the microfibers and then clamping together.

It was quite warm last night so the pot life of the resin was going to be short, so I worked as speedily as I could. It is a fine line between getting it all done before the resin goes off and going so fast that mistakes are made. I think I got it right, just as I finished the mix was setting.
I am using West System Epoxy as shown in the previous post.

I need more clamps really.

Scrap wood to spread the load.



The rear stay blocks will start as five layers of 9mm ply, but i have only laminated four at the moment. This block will be for the bottom rear stay and it needs a grove cut into it to take the bottom bracket reinforcments. Last time I had to retro cut this into the already shaped stay and it wasnt easy, so a lesson learnt, I will cut the grove in this block then laminate the final layer to cover the cut.

Just enough pressure to get good contact with the resin.

 

Once the resin is all set I can start the proper carving and shaping.

Epoxy resin

I splashed out on the West System epoxy resin for the build today. Hopefully this much should be enough.... It was last time.

Making rear stays.

So having done a lot of thinking and working out on paper, I decided to test my ideas. So I set out to prove myself wrong. I made a straight stay, and to be fair it could be forced work, but not very well.

So having proved that I was correct in my assumption about shaped rear stays, I set about making them.

 I cut a test shape, but forgot to allow for the extra clearance for the disc brake, so I started again. Here is the revised shape, with extensions to all the ends to allow for trimming. One thing I learnt from the www.plycycle.co.uk project was best to have too much and cut it back than not have enough and wish you had more. Its like any type of carving, or reductive sculpting, once it's gone it's gone. Having spent ages marking out the straight stays, I dove straight in, marked out the vital measurements and drew the rest free hand. I like the more organic approach.

Final shape with extension for disc brake clearance.



Having got the shape how I think it needs to be, I cut more. Four for the top ( the top stay is slightly longer at the top where the frame connects) and four for the bottom.

 

 

Here they are stacked up ready to be laminated together. I will go for West System epoxy resin again as I got to know its curing behaviour on the last bike. I have found that the local candler has started to sell it, so I won't have to trek across town to get it like last time.

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.