Bits n Pieces

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I actually started with these as they were the easiest to make and were also the smallest so I just about had enough wood to make a new part if I messed up. A luxury that I didn’t have for the main frame of the bike!

All 3 layers of wood have the grain running along the length of the stays. This is perfect for developing the strength and stiffness in the stays but I’m worried about what happens when I drill a great big hole for the bottom bracket and then put a big force perpendicular to the grain. I don’t much fancy my bottom bracket dropping out on the road! So, I’ve reinforced around the BB by putting 2 layers of 175gsm fibreglass tape with the strands running perpendicular to the grain inbetween each sheet of wood. This gives me 4 layers per stay. I don’t know whether this will be enough but I plan to put more reinforcement in the main bike frame so the combination of the 2 should hopefully be ok. When wetting out the fibreglass with epoxy make sure it goes completely see through to avoid any dry patches in the joint.

The stays were rounded and the ends bevelled with a router

Aluminium Parts

Head tube, part of set tube and bottom bracket from the donor bike cut to size and welds filed down. I’ve deliberately left the surface fairly rough to give a decent key for the glue to bond to when I glue them into the frame. I didn’t drill any holes in the seat tube as the seat post is such a close fit into the tube I thought I’d probably end up with either a jammed seat or a seat post that wouldn’t fit in the frame if I tried to do anything to the tube.

Swiss cheese head tube? I used a hand drill to pepper the head tube with holes to lighten it. All the forces will go throught the solid bearing mounts at the ends of the tube and into the wooden frame so I’m not too bothered about weakening it in the centre. I’m undecided as to whether I think the holes will increase or decrease the strength of the glue joint when it gets fixed into the frame. It feels like it should give it a bit of a mechanical key to grip on to but there is also a smaller surface area of tube for the glue to bond to… any ideas? Oh, and the lip that you can see at the ends of the tube was just a feature of the donor bike. Nothing that i’ve done. Although, i’m going to use it to wrap more fibreglass tape around the head tube to tie it into the frame.

A couple of shots showing the internal cable guide. It’s made from some 8mm aluminium tube that I picked up at Homebase. I wanted some plastic tube but couldn’t find any so this had to make do. I just bent it by hand with a little help from a vice and it’s big enough for the brake outer to slide through.

Drop outs cut from 6mm aluminium sheet ready to be glued and screwed into the stays

Brake bridge cut from 6mm aluminium sheet and slotted and glued into the seat stays

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13 thoughts on “Bits n Pieces

  1. Hi Nick,
    I’m currently at university and so happen to be creating a wooden aero road bike. I also found the Renovo bikes very intriguing. For my first one I’m using Ask with a purple heart centre but i was intending on using Hickory instead of the ash.
    I have a lot of questions but you’ve answered so many of them already.
    -With regards to the piping you up in the top tube did that work well? and what size tubing do you recommend?
    – How thick is your ‘walls’? I’ve designed it so that theres 1cm around but on your it looks thinner.
    – Also you mentioned about your chain stay’s I find it incredible that there so thin do you get a lot of flex?
    – I’m thinking about having an Integrated head tube as I thought that the headsets would be too chunky out the top of the head tube.
    Sorry about all the questions but I’m sure that I will have many more. Will make sure to link you to my page once its done. Would be great to see what you think.
    Wicked page, thanks in advance.
    All the best

    • Hi Joe
      Lots of questions!
      1. I used aluminium tubing that had the same internal dia as brake cable outer. It’ll rattle if there’s any movement. You can also get brass tubing that just fits the inner cable which is easier to use. I also looked at pvc tubing which would also do the trick

      2. Read my page ‘let’s talk numbers’ it goes into some more detail about tube thicknesses. The tube thickness is related to the diameter you’re using and how stiff you want the frame. I’ve tested 2mm thick large diameter tubes that are stiffer stronger and lighter than aluminium if designed and built properly. 1cm wall thickness will give you about a 5kg frame on its own! Aero profiling won’t help much when you’re on a 12kg bike.

      3. You want thinner seat stays for vertical compliance and larger chain stays for lateral stiffness. You’ll find fitting thick chain stays is a bit of a geometric mind bender to avoid clashing with the wheel or chainset. Possible though. Look at some of the chunky carbon frames with asymmetric chain stays.

      4. When you say integrated head tube I assume you mean that you’ll bond in a metal integrated head tube. Don’t try to press fit a headset straight into the wood.

      What course are you doing at uni?

      • Hi Nick,

        Thanks a lot all this is really useful!

        Was wanting to go thinner in the walls but wanted my first one to work. You got a recommended thickness? With having aero profiling all over the bike and karma tails it should be strong enough for roughly 6mm wall thickness. The down tube varies from 60 – 42mm too 70 – 42mm. Haha yea I totally agree its about finding the equilibrium between weight and aerodynamics.

        You say vertical compliance what do you actually mean? If they were too stiff would it cause more vibration and become uncomfortable? or lead to breaking?

        I’m just looking at the Chain stays now like you said its becoming a bit of a nightmare to fit! But having seen your’s its given me the confidence to go thinner. Which will undoubtedly make it a lot easier.

        Yea I’m brazing 2 integrated cups onto a straight 1 1/8 tubing. Then that will be inserted and bonded into the head tube. Didn’t want the standard headsets as I didn’t think it would flow very well with the head tube I’ve designed.

        I’m a third year doing Product Design at York St John University its a pretty decent course but this kinda stuff doesn’t happen every day. With it been quite far fetched it’s just been a lot of guess work hence why i over compensated for the wall thickness.

        All the best

  2. Ha! Check out my work in progress build…… looks familiar!

    Make sure you model the cranks, chainwheels (double and triple), front deraileur, chain, wheels and rear casette otherwise you’ll end up having to do some last minute modifications with a file! You can get all the manufacturers component dimensions off their websites.

    There are 2 types of stiffness. The first is up/ down when you hit a bump/ ride an uneven surface and you want the frame to be compliant (flexible) to give you a smooth ride on rough surfaces(read about the Trek Domane). This is all ‘in plane’ of the frame. The double triangle of a frame is naturally very stiff so making the seat stays smaller is the most effective way of softening the ride at the seatpost.

    The second is the lateral/ torsional stiffness of the bottom bracket which is ‘out of plane’ of the frame. You want this to be as stiff as possible to transfer pedal forces efficiently to the wheels with minimal losses. Hard pedal strokes twisting the frame are resisted by a combination of opposing forces on the handlebars and gripping the seat between your thighs. Hence a large diameter down tube to carry twisting forces to the handebars and a tapering seat tube from the seat down to the bottom bracket.

    I can’t tell you what thickness to make the tubes as it’s a function of the wood/ glue that you use, the tube sizes and how you joint it. There’s obviously a balance between making it too thin and the frame becomes too fragile (top end carbon, steel and aluminium frames are on the limit in this respect) and making it too heavy. By the sounds of it, 6mm should be fine but will produce a fairly heavy frame. Why not make a series of test tubes and break them to work out how fragile you can go? 6mm hardwood is stronger than any frame on the market.

    I’m obviously coming at it from an engineering perspective – materials, stresses, stiffness – but a product such as a bike frame can only function well when these are a core part of the design as there’s not much room for error if you want to design a decent frame with a balance between weight, stiffness, comfort, aesthetics and aero (last on the list!).

    Are you planning on CNC cutting the frame?

  3. Well were kinda on the same tracks! Pretty cool that! love the colour too will definitely be eye catching!

    You wouldn’t mind telling me the height of your front derailleur hanger would you! been trying to find the manufacturing standard for some time now! That would be another job done!

    Yea I’ve modelled out the components that I intend to use just to be on the safe side! Got a few minor niggles when I assembled it the first time but now working on making sure it would be fine with various component sizes.

    It interesting you say t6mm hardwood is stronger than any frame on the market, would love to do all the testing for the frame and see which was the best for every component but I’m afraid time isn’t on my side. With this been built mainly for my degree I have to have this designed and built in the next few weeks.

    Yes luckily I am using a CNC machine but it’s only a standard one now a 3 axis cutter. Using the CNC machine has actually been quite a farce as the stresses the machine puts onto the wood can cause it to rip out of its ‘holds’ in the bed of the CNC machine which as you can tell isnt good!

    You also said in an earlier comment that you heard that Renovo machine a side in 6mins where did you read that as I struggle to imagine this been possible! Seen as to machine my bike is going to take hours per side. Really good if that is the case though! Machining cost would be significantly reduced!

    I’m planning to refine this bike as much as possible well after university so the tube testing will be first on my list! The bike will most likely be too heavy first time round but with me been judged on it I wouldn’t want it collapsing after manufacture as this may jeopardise my degree and overall grade.

    Oh one last thing how did you manage to do the finger joints so cleanly did you use a spindle cutter? Was wanting to use this but wasn’t aloud due to university reg’s and outsourcing it would have cost a lot! If theres a simple way you know may have to change it to that as that was my desired joint!

    I do really like your other bike and i hope you get as much appreciation and attention as you have done for this one! I’m guessing your an engineer also?

      • Yea sorted it all now! has to just tweak little bits here and there! Its done so i have minimal sanding to do so i dont mess with the aerodynamic calculations too much.

        Just finished laminating all my wood! Now the waiting game!

        The links great! will defo be cross checking everything just to make sure!

  4. Answered one of my own questions! You’ve already said that you bought a finger jointer for the router. Was it expensive and easy enough to do? I will stop with the questions soon! just spent so long going through stuff in my head with no one around me having a clue what I’m doing.

      • No I’m been told to biscuit joint it and not CNC near the joint on the inside but im trying to get someone to let me use there tool bit like you suggested above. Just far too expensive on my budget. I dont want to use anything else but the finger joint so if i have to will have to purchase one. Emailed a lot of local joiners etc.

        How far along are you with the other bike?

      • I would be nervous about using a biscuit joint as the joint is only as strong as the biscuit. A finger joint bonded with epoxy will be as strong as the full wood section. You can finger joint with careful use of a band saw or alternatively a very thin diameter router bit and a router table. Google it I’m sure there are youtube guides.

        If you biscuit joint it, can you fit 2 biscuits per frame half one on top of the other (i.e. 4 big biscuits per joint)? And make sure you use hardwood biscuits (or metal) not the standard out of the box biscuits.

        Having already laminated the wood you’ve missed the boat on being able to half lap each layer

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