Your force/displacement graph will change depending on the velocity because of damping, so you will need to produce a range.

Check out this paper http://www.mech-ing.com/journal/Archive/2010/4-5/1.Mashini/75_gavriloski.mtm10.pdf seems to be pretty on it in terms of air spring modelling.

This forum post, https://www.physicsforums.com/threads/air-spring-stiffness-calculation.520833/ also provides a non-linear equation which looks more sensible than simply using adiabatic compression, particularly as you would be assuming instantaneous compression/expansion which isn’t always the case.

If you google it there is also quite a bit on rolling lobe stuff for trucks which are just air springs, I am sure you can find something on them.

I went 1x because it was easier than learning how to set up a front mech (I still me maintain they work by magic). That any my bike at the time was a not-so-lovely BB386 crank with a 26/42 chainring combination, I found I was cross chaining in races and when I did try to shift up/down on the front I would drop the chain completely, so decided to go to 1x instead, because it was just simpler.

Because standards, why should you be able to buy anything with backwards compatibility? That would be far to simple.

Jamie,

the project is still going, about to purchase spokes and rims after speaking with my wheel builder. When these guys get back to me then I will use their system on a ambrosia zenith double fixed track hub. My thinking being if its good enough for track riders to brake against a lock ring then it is good enough for me (probably fine), and I will use thread lock on both the adapter and the lock ring. As it is a track hub with cartridge bearings I will be making my own lockring/nylon washer to provide a hope style shield from mud to avoid having to strip it down after every ride. I am still waiting for broaklands to tell me if I should buy the phil wood/campy lockring of the ISO, seen as sheldon says that ISO is the campy standard and JIS is the shimano *confused*.

I have a hope pro 2 evo trials rear hub now ready to build up for the rear wheel and I have some 2010 boxxer crowns to make my forks with to avoid having to buy a crown race cutter, thankfully the hub fits in between the stanchions so it *should* be an easy fix. Weirdly I will also be making my own stem, two of them infact, to attach to the stanchions rather than the standard clamping point for bars (think the way clip on aero bars work).

I am going to use 3 (yes 3) BB7 road calipers as that is what I have lying around, I have the brake levers (some chepo tektro ones from on one) now and will use something similar to a jteck double pull adapter to pull both levers and equal amount, again this is something I will make.

The rest of the build is still going, currently trying to validate some of the FEA testing on a formula student car, once this has been done then I am confident that a bicycle will be validated as well given how simple it is in comparison. I have decided on using plain gauge T45 tubing as its cheaper and I will be using fat bike standards at the rear end (100mm BB and a 135mm rear hub offset by 15mm, think a surly pugsley) which means I can split the seat tube to make it look a bit like a fork and have some super slammed chainstays to make it not handle like a boat. Need to finish deciding on geometry (which I will be going over to mtbr for advice on, as they seem to know their stuff) then I will be able to buy tubes and get brazing!

Sorry for the essay but you did ask 😉

Oli – you are getting no where near this build!

edit: almost forgot! I am moving away from 4x and to 3x because I can only buy the length of spoke required for 3x, I am having to vary nipple size to build the wheel properly, which is fun.

What about fatbikes? Would also be interested to see the geometry changes and how santa cruz accounted for that.

I have to agree, they are pretty fun when not in the snow but they are something else in the snow, just fantastic. I wasnt expecting that much of a difference.

What standard are they?

Unless you get an extender (see one up, absolute black, hope trex etc.) that isnt going to happen, change the smallest chainring to a smaller one?

You can’t get turn-by-turn but you can overlay a GPX plot from bikehike (or similar) onto the OS map and then follow that.

Get an etrex, I manage to navigate a CX bike over 95 miles of the moors with a 30. The only thing they aren’t that good at is being run over by range rovers, they tend not to like this and it should be avoided.

Also the bike mounts are sh*t, like really sh*t and I have seen on the bear bones of someone modifying it with inner tube to make the attachment tighter. I have also seen people tying it to their bars with a lanyard for when it does vibrate free from its mount.

That looks lovely! I like that metallic green.

Really want to get some 29+ tyres on my KM but its a bit pricey just to try.

I know I am a bit late to the party but I ride it on everything, gravel, singletrack etc. 3PCX was a highlight as was the world cup XC route at dalby, just have to ride everything a little bit slower. Also attempted a dirty 100 miler in the moors over gravel and bridleways and ended up with my collapsing in a silly mess.

Do it. They’re great.

I don’t know for sure if you can fit a 29er tyre in that frame but considering it says 650b I’m going to assume no.

http://www.unicycle.uk.com/unicycles/road/36-udc-unicycle.html 31.9″ inside leg for the minimum size, waltworks does some properly ‘gnarly’ tyres that are like a kenda neverolls but in 36″

Everyone – absolutely, why else would I want one?

36″, brings the trails alive, probably.

I have been hardtail only, but have decided that forks take too much looking after, so have now gone rigid instead, have got some sus forks just in case I fancy it though..

Ben, what the hell were 65mm spokes for?! not the suspended wheel was it? I am aware that its not always the way, but considering I was going for a twin BB7 brake on the front wheel, I wanted something a bit… more likely to survive.

Mike, I am tempted as I said on the ride today. Oli, you dont trust a FRAME from ali-express, so why would you trust spokes?!

aracer, 36 holes, I hoped that having one spoke length throughout the bike would mean carrying any spares would be simpler. I was going to use 4x to just make the wheel as strong as possible, the front wheel will have a dual disc system implemented so really didnt want to over stress the wheel. I can indeed get away with 367mm spokes if I go to 3 cross.

Stick with the hardtail, less things to go wrong.

Stupid idea, point loading outside of the triangle on the rear bike on the down tube?! Guys f’n nuts. Also, is that a “double rim” rather than a fat bike rim?

Turbo,

Id be more than happy to. I am also about to do an FEA validation on a space frame chassis, and a bike frame isn’t that far off (and an awful lot simpler). I will be doing some for various things I’m attempting so it wouldn’t be any bother at all. A lot easier to do multiple FEA than to build multiple prototypes.

Nath,

If I had time to ride at the moment, you would be one of the first people to know about it. Ill be coming on the hip flask ride on my very ‘responsive’ frame, it delivers power instantly. It appears to be the holy grail – may be a placebo because its my baby.

No SS yet, probably won’t get SS’d, only need one SS and its the fatty at the moment, then the 6squared.

Sorry for the thread hijack.

I have niners on mine, they flex where you want them to (along the bike) but not where else (very stiff in torsion). I like them so much and find that they are perfectly capable of handling everything I an throw at them that I am using them all year around instead of just the winter. If you could get some chunkier grips that would help, you get used to the harshness anyway.

Do it.

If you want some decent FEA doing (i.e. not the SolidWorks solver) I have an MSC Patran (technically Nx) license that’s good for linear stuff. If you sent me the model, constrains and materials of each I could perhaps have a bash at it.

http://www.identifont.com/ this is a good site for this kind of thing.

edit: looks like EF DIN 1451 Eng Neu

At one end I have a karate monkey set up as a drop bar road/cross bike (lovely mud clearance) and at the other end I have an SS Pugsley. Inbetween I have a rigid 29er set up as 1×10. Not all that different to each other if I am honest.

Why not buy from reynolds? They sell direct and you will struggle to find a stronger steel than 853 (without going stainless), also pretty easy to braze with. Paragon in the states do some fancy drop outs (like the 12mm bolt through that I used). I used Ceeway for my pre-bent stays.

I do realise my brazing is messy (been told if it was a horse someone would have shot it by now) but I got bored with filing it down and it won’t make it any weaker, probably.

Leisure lakes daventry experience here. They managed to crush a tube on the frame that I built, no idea how would have taken a tonne of force to crush an 853 tube in a park tool stand. Dragged their heels a bit (as the store owner was on holiday) but ended up negotiation on the price with them and they paid me a reasonable price for my trouble. Also claimed they had tools they clearly didn’t (as they didn’t carry out the work in the end.

8/10, would never go there again for any work being done on the bike but would buy stuff there. They were sensible and weren’t giant numpties.

That is a LONG rear end.

So what your saying is you bought a 29er frame and then ran it with 26″ wheels? Watch that ground clearance.

No, Ive worked out (in my head with my housemate) that the air in your tyres isn’t a rotating weight (until youve been riding for a while and there are boundary layers taken into account) so only counts once, so you’d only reduce the static weight, and probably not by that much tbh.

edit: youve also got to get hold of enough of it, goodluck!

How about fire and explosions?

*pst* probably not a smart idea on smaller volume tyres

Well not sure how they make money off of 600 quid for a 853 tubing, all the parts for mine cost me £450, doesnt leave a lot of space for consumables and time!

I’d personally if not making my own go and see Lee Cooper, he is down to earth and has been doing it for ages, quoted £800 for 853 steel mountain bike (with my getting the fancy 142×12 drop outs)

and void your warranty (potentially), and put more stress through your frame leading to possible breakage. I wouldnt.

If you have the money to consider a custom I would put another vote in for building your own with dave yates, or if you have access to a workshop build your own. Nothing compares to riding your own bike that you designed AND built, fact.

As has been said on here before, you can make bikes feel very different with something as simple as axle standards, wall thicknesses, tubeset, OD’s etc. So either you need to know what your doing or work with someone who does. I manage to make my 29er stiff as hell with a 142×12 rear and 853, when you put your foot down it just goes, not a featherweight though but it does track like a beast.

Koolstops were the best pad I found for my CX70’s, good pads but do wear a bit quickly (side effect of them being such a soft compound).

If you still want to face it (depending on where you are based), you can use my 44mm reamer/facer for the price of a pint.

Go on then, give us a piccy!

It also appears that I uploaded the incorrect “working” version as that one didnt work! Heres the correct working version.

I have just bought some 24″ inner tubes to redo the rear, its a right PITA re-inflate with this method (as my tye decided to unseat both sides during the night). Also built the centre up with foam so with the new split tube method hopefully it will be easier!

I couldn’t find a butane/propane refill at the time!