Cutting n Gluing

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Day 1 – All the parts ready to go. All that is needed is one careful woodworker.

You can see some of the tools i used laid out in the photo. Here’s a list of the essentials:

– Jigsaw – Router – Electric hand drill – Straight edge and square – Stanley knike – Small hack saw for fine cutting – Sand paper (all grades) – Plenty of clamps – Double sided tape for sticking small bits to the bench and each other while using the router – Metal file for the aluminium parts – Dust mask – Goggles

When i first started thinking about this i thought i could probably do it with just a jigsaw and a drill. I was wrong. I don’t think you get nearly enough control with a jigsaw to be able get a good finish and the round over and bevel cutters on the router made forming the shape of the tubes so much easier. In fact i think i’d still be going now if I had to do it by hand!

Another quick note before we get on to the fun bit. WEAR A DUST MASK! Hardwood sawdust is an irritant and leaves you feeling pretty funky if you breath it in whilst working on it. I learnt the stupid way and always wear a mask now. Goggles are also handy as you quite often get little bits of wood flying out of the router which aren’t so healthy for your eyes if you’re up close making sure you stay on the pencil line.

I read somewhere that it takes 6 minutes on a 3 axis CNC (computer numerically controlled) router to shape one side of a Renovo frame. I like to think of my method as CCN technique – ‘Carefully Cut by Nick’ – Every part has been painstakingly made by me, although this method does have the disadvantage that Renovo will probably have made dozens of better bikes in the time it takes me to make one!

There was quite a lot of work to get to the photo above. I created a CAD template for each layer to set out the size of the different internal cut outs from layer to layer. I traced around my CAD drawing to mark one of the pieces for each different shape. I then carefully cut out these pieces using the jigsaw for curves and the router for the long straight edges so that i could use the router edge guide against the edge of the bench. All the remaining pieces were then copied off the templates using a roller guided straight cutter fitted to the router.

The internal cut outs were cut out in pairs using a straight cutter. I then bevelled the inside edges with a 45° cutter to get closer to the round inner profile.

Down tube stacked up before I made the half  joints. All the pieces are identical due to the guided cutter that i used to follow the template pieces.

Here you can see the routed profile in the inside of the bubinga outer layer. I thought this was going to be tricky as i hadn’t really used a router before. It turned out to be pretty easy with the edge guide on the router. If I did this all again, I wouldn’t bother cutting out and shaping all the internal holes in each layer. You can see took quite a while. I’d simply glue up the solid pieces and route out the insides in one operation. You just can’t afford to mess it up once all the layers are glued together!

Half joints – another essential job for the router. The pencil lines parallel to the half joints show where I clamped my straight router guides to get the cut in the right place.

Seat tube half joint

Head tube half joint

BB half joint

I only half jointed the inner and outer layers with the wenge layer butt jointed. The half joints were also offset 6mm-4mm for each 10mm sheet. This meant that for each half of the frame there were 3 layers in one direction (4mm maple -6mm wenge – 4mm bubinga) and 2 layers in the other direction (6mm maple – 6mm bubinga). It felt like that would balance the joints well without me having to half joint the thinnest layer.

As an afterthought, whilst the half joints allow a large glue area between each layer and also allow the wood to have much better bi-directional properties at the joints, they do take a long time to form and are difficult to do really accurately. I’d be interested to see the difference in strength between the half joints and the Renovo finger joints. The finger joints would certainly be a lot quicker with the right tool. The finger joints also allow you to make up solid laminated pieces of frame rather than having to work on each layer individually.

This is the seat tube, you can see the step between the different layers before i profiled each of them and routed out the inside of the bubinga outer layer.

The sticky stuff.

You need plenty of good clamps and some good blocks of wood to make the clamps work over a large area. I’m laminating all the layers together here once all the joints had been glued up for each layer. You can see lots of plastic shopping bags. They are one of the few things that epoxy won’t stick to. I’ve got a few on top of the plans (to save the expensive maple flooring!) and a few in the middle to stop the 2 halves of the frame sticking together. Try to only use the back side of the bags as the print on the front of the bags tends to come off on the glue and you don’t want to end up with it on the wood.

And here’s something else that epoxy doesn’t get on with. PVC electrical tape. Wrap it sticky side up and it is really easy to remove. Use it to clamp bits together or use it to give a nice smooth finish to the epoxy coating.

Here’s one half of the frame after gluing up but before shaping the outside. I cut out the bottom bracket hole using a 45mm hole saw in a hand drill mounted on a makeshift pillar drill.

I did the cut outs for the stays using the router and just following the pencil lines by hand. I marked the pencil lines using the same full size templates that I used to set the overall geometry. It took a few goes, gradually increasing the size of them, to get a snug fit for the stays.

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9 thoughts on “Cutting n Gluing

  1. Hi,

    Brilliant bike and description of your construction process. Very inspiring! I have a question about the CNC method for this. From a structural perspective, Is it possible to use only 1 piece per half of a tube (say 25mm thick) milled out with the CNC to give the required tube thickness and joined together top and bottom with another half tube? I’m a student and was thinking about making good use of the latest equipment in the workshop.

    Thanks,
    Tom

    • Sort of…If you’re thinking plywood then it’ll work but will be too flexible to be a decent alternative to a conventional frame. If you’re thinking hardwood then you need the grain to align with the tubes so will need to join the pieces together at the corners. A fine finger jointer will do the job. Think carefully about the wood you’re going to use as that will define the performance of the finished frame. Then CNC the triangle that you’ve pre made. It won’t look as pretty as the laminated layers though!

  2. Hi
    How did you get the right angle for the chainstays and the seatstays so they would fit the rear weel hub? Did you give the cut outs in the frame an angle or is the angle somehow in the stays?

    Beautiful bike you made!

    /johan

    • I chamfered the ends of the stays by making a template at the right angle, clamping them so that the line I needed to cut on was horizontal, and then used the router to machine the surface. I had to do a little fine tuning by hand to get the drop out spacing just right.

    • Hi Wojtek
      The frames that I’ve made vary in thickness from tube to tube depending on how stiff/ strong I want them and what type of wood is being used. There isn’t one answer to the question. The thickest I’ve used is about 5mm and the thinnest is about 2mm in places although you need to be sure of the stresses in the frame, the accuracy of construction and the suitability of the wood to even consider that thin.
      Cheers
      Nick

  3. Hiya Nick, Love the build. Ive got my head round doing the routing of the sides via the adjustable slide on the router. I’m stuck at how to rout the stays “pocket” in the main frame. Theres no edge to run off from so any help would be great.

    • I just mark it in pencil onto the wood, set the router on a stable horizontal base and carefully rout by hand without a guide up to the line. Not as hard as it sounds although not much room for error

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