Woody 2

I haven't really unleashed the geek on you guys yet so far this build so here's some info on some background studies that I've been doing on the side.

The main difference between this build and the last wooden frame is the thickness of the tubes, all in the name of reducing frame weight. However, at less than 3mm thick in places it worries me that the frame may be too fragile. I've done the calculations to convince myself that the overall frame will be strong enough and stiff enough to perform well (similar to other high performance frames) but side impacts on the tubes are harder to check and there are no standards that give any tests or requirements for impact resistance. We've done some FEA modelling (computer stress analysis) to check this, using conventional steel and aluminium tubes as benchmarks for 'impact resistance', but the orthotropic and highly non linear nature of the wood makes the analysis difficult and the results dubious.

So, i made a test sample. 2mm thick Ash with internal stiffeners

The tube was very fragile before the stiffeners were fitted but felt very robust once glued together and only slightly heavier than a Columbus Airplane alu top tube.

I set up a highly technical test rig with a G clamp and my bathroom scales #backyardengineering

Crank puller taped to the G clapm to apply the point load!

Here's the wooden tube and a section of alu seat tube after being taken to failure

You can hardly see a mark on the wood but the alu tube is clearly dented.

Now for the interesting bit. What were the results? I did quite a few tests but have distilled the results into this graph

The sharp eyed will spot that the curves should be linear at the start (before the samples have yielded) I think the odd shape os probably due to my highly non technical test rig and some 'bedding in' movement that happened in all the tests (the foot pad is slightly spongy!)

The alu tube failed at a much higher force than the wooden tube, which dissappointed me as i was expecting it to perform better. I've also plotted the 'reload' curve after I reloaded the wooded tube several more times. It performed reasuringly (suprisingly) similarly under smaller loads despite having clearly failed in the first test.

However, I spotted something quite promising. What if we're not interested in the size of the impact force, but rather the energy of the impact. This would be equivalent to dropping something on the frame, or dropping the frame on something and absorbing the impact without damaging the frame. The energy absorbed by the tube is the area under the curve, which, is considerably larger for the wooden tube.

So, despite failing at a lower load, the wooden tube can actually withstand a larger impact because it is more flexible and deforms more enabling it to absorb more energy.

What this does not show is the post yield energy absorption as the alu tube would have a much better post yield behaviour.

I'd love to do the same for a carbon tube to see how it compares.

Anyone got a write off frame that I can cut up and test?

So the conclusion is that I'm quite happy with the robustness of the tubes compared with an off the shelf alu tube and the actual frame is thicker than my test sample (I got chicken) so will be stronger.

To put the test numbers into perspective, the wooden tube failed at around 110kg with a point load of around 1sqcm. I tried jumping on it (80kg) with my heel and hurt my heel but not the tube.

QED

I posted that in svendsvin's thread with the diy hydraulic brake levers etc., you're on the same level of madness just a different project. There are quite a few mad scientists on here!

this remains my stand out favourite project on LFGSS at the moment. Your stress testing is fascinating, and impressively detailed.

When I was reading the forum of your single speed project, you said the bike wasn't as stiff as the Condor, now when I was shopping for track frames, I noticed some older track frames had been filled with expanding foam to improve rigidity.

Your level of realisation is most excellent!

The single speed frame is at least as stiff as the steel Condor frame but is more comfortable as it absorbs vibrations better. It's not as stiff as large tubed alu or carbon frames though. Most of the flexibility that I've noticed comes from the lateral stiffness of the rear stays. I'm going to see how the stays on this frame feel when all glued up and may need to add an extra lamination to the inside to stiffen them up if need be.

Megathread, five stars!

Extremely well done, hats off.

Once again, painfully slow progress so no new pictures but it's getting pretty close. All glued up drop outs made, mech hangers aligned and fitted and final sanding in process. Almost ready for varnishing. But, before I do....

does anyone have a head tube and seat tube reamer and facer that I could pop over and use in return for beer/ wine or recommend somewhere (cheap) that will do it for me?

Might be ready for the planned finish date in June for the big rides this season..... oh, wait.....bugger.

Cheers
Nick

I have reamers. Pm me.

Amazing. PM sent. Cheers Nick

Big thanks to Matt at Talbot frameworks for help with the reaming (think I managed to avoid the innuendo there). Very helpful and knowledgeable chap. I also got to see his clever integrated di2 frame from Bespoked with the electric cables painted onto the frame in silver filings.

Final sanding and varnishing still to go before its finally complete.

Nearly there. A couple more coats of varnish to go. It changed colour dramatically when I put the first sealer coat of epoxy on so the red components that I've got for it aren't going to work so well now. I've included a before and after pic to show the difference. I've also never shown a pic of the drop outs so here they are ready to go.

leave components plain as possible. no colours.

take good photos afterwards

Better pictures, now, would amaze equally.
And please unleash the geek any time.

Got a pair of these to go on it

Unfortunately I'm limited by the terrible light in my spare room and photos on a camera phone. After 6 months I'm afraid you'll have to wait a few more days for decent pics when I can get it out in the sun after a few more coats

are you serious?

I'm really looking forward to proper daylight pics of your work though.

Err... no.... only joking. I was expecting more of a reaction though. Maybe it was that obvious.

Loving it. Went and read the website for Woody 1. Thank you for providing great literature for the builds, has inspired the carpenter within me to have a go at this myself. Brilliant stuff !!!

Frame done.

Its difficult to get the colour and grain to come out properly in the photos. Here's a shot with and without flash to show what the light brings out. Needs a bright sunny day to get the best out of it.... so maybe I'll get a decent photo next summer!

And the moment we've all been wating for. Only first fit up because, stupidly, I hadn't realised that the donor bike that I have has 1" forks. They also look a bit spindly as they were on a steel frame. Ordered some chunkier forks to go with the enourmous down tube.

Also still needs Ligneus logo and bottle cages.

strong work there!
what's the frame/total weight?
also, please make a matching wood head set cover/spacer.

Frame weight is bang on 2.2kg, which is disappointing. Thought I was going to be able to get under 2kg. Haven't done an all up weigh in as it's not all built up yet.

Speaking of which, there's no headset in the photo above. Not sure I have the patience to make wooden spacers now. Just want to get riding! Cool idea though.