psycholist

What is the 'A2'? If you're looking for an engineering type project I have a few ideas (Given that I supervise final year mechanical engineering students and tend to give them bike related projects, there might be something of interest for you). Here are a few past and current: Design and build a test rig for brake power testing to EN14764:2005. Brake testing to EN14764. Design, build and calibrate a spoke tension meter. Finite element modeling of a bicycle wheel. Precession and its alleviation in threaded joints. Design of an alternative to a derailleur based bicycle gear system. Design of a hydraulic gear shifter, preferably open system and self indexing. Measurement of pull out forces/clamping force repeatability in front quick release skewers. Optical electronic measurement of wheel trueness.

Add 1.5" to the chainstay length of a trials frame and unless you're really tall it'll be a complete pig to get on the back wheel... To counter this the handlebars could be brought further backwards, but that would lead to loads of overlap (With a normal wheelbase it's already tight and with 29" wheels there will be more anyway) between your toes and the front wheel... 26" wheels are about as big as you can go for trials unless you're very tall. 29ers are a solution to a problem, namely that the man made trails built by the forestry people are so boring and unchallenging that a modern bike with suspension is complete overkill for most of them, leading to loads of people using rigid singlespeed 29" wheeled bikes on them in order to bring some bit of technical challenge back to the trails - I know this because the best day I've had on official MTB trails was when I took my 19 year old Specialized rigid with canti brakes out ... Trials has no such issues with becoming less technically challenging, so no justification for 29ers...

I was hoping all the talk of failed forks wasn't something for me to worry about, but this happened my urbans last night: I was landing from an 8 inch drop at the time... Failure was due to fatigue cracks (In both legs), starting from the tops of the welds where the Magura mounts are fitted. Rim brake mounts on the front of the fork seem to be a better idea from this point of view incidentally (Fatigue cracks can only start at areas with tensile stress, and the back of the fork will see more of this in general use). I ran Maguras at the front up till about 3 weeks ago, then swapped to the K18 Formula. Can anyone recommend a steel fork the same length as the Echo Urban? Steel forks still fail (I've had enough of them go on me to be sure of this, but never in such a short time and never as a catastrophic failure that's dumped me onto the ground hard - they all kinked or cracked at one leg and bent rather than snapping), but at least steel gives a decent warning and bends/creaks/shows rust at the crack before finally failing.

Here's a classic: - the first 1:40 is introduction though - anything you put this music to will be less disturbing than the official video ...

It depends on the concentration of the caustic soda solution and the thickness of the anodising. Best thing to do is apply it to somewhere on the rim that won't be seen (The inside where the rim tape sits is good for this) and wipe some of it off every hour, leaving the rest coated until you get a result you like, then coat the exposed parts of the rim and leave it for that long before cleaning it off... Since you're aiming for bare aluminium you don't need to be that scientific though, any unevenness should come out as you polish the rim afterwards.

My bad - I was reading from about half way down and saw it being called paint again ...

Statistically given the gender breakdown in trials this person is a lot more likely to be male, secondly in English it's grammatically more correct to use he as the pronoun where he or she is a possibility. If this is a lead on to the People's Front of Judea campaigning for Stan/Loretta's right to have babies then ignore me ...

First off - is it paint or anodising? I think all the tips given have been for removing anodising and not paint. I'm not sure what will strip paint from aluminium and not damage the aluminium. Try nitromors or a heat gun if it's paint. DOT fluid also works as paint stripper...

All the long pawls engage at the same time, all the short pawls engage at the same time. The engaged sets of pawls are arrangd in a triangle so as to reduce the tendency of the pawls to push the freewheel off line under load (Shimano freehubs and I think some of the Rolf ones have two pawls at 90 degrees to each other in their XC wheelsets to share load between the freehub bearings and the pawls, but in trials this arrangement would drive the freehub too far off line leading to failures). The difference in length between long and short pawls on an ENO is 1/72 of a turn and the ratchet ring has 36 engagement points... Not much more to say on it - it's a simple and very effective design if you use good enough materials (Like the ENO does).

Were the pawls in the correct order? Every second pawl should be a long one.

Mine has never ever skipped since I got it 8 months ago... There should be no such thing as 'breaking in' for a ratchet and pawl setup unless something is jamming the pawls - open it up and make sure nothing is jamming the mechanism...

How will changing to a 2 bolt booster stop you needing to cut your pads down? Unless you're using Evo mounts and find a booster with a wider spacing than the default one you'll still need to cut the pads down to make them fit. Do the pads foul on the brake booster or something?

To fill the gap on the inside of the freehub body to give me the correct chainline for a 22:17 gear ...

It's a good idea to run the chain as short as possible - just make sure it'll handle the lowest gear. I used to run a 22T chainring and an 11-23 cassette and it was fine. If you're running a front freewheel it makes no difference (Provided you can get a fixed freehub hub )... Try to set the chainline so that the gear you use most for trials lines up perfectly with the chainring - otherwise you're more likely to get the chain skipping every so often.

What sprocket are you running at the front? Without that there's no way to tell if 16 tooth is suitable.

I find the same thing with font wheel first landings when I hop in the direction of my lead foot. There is definitely a height benefit to going front wheel first because you can pivot the back wheel up by loading the front and the bike spends less time in the air and can be controlled more precisely with a wheel on the ground. Practicing hopping over a tape removes the front wheel first option too, so you can compare hops to each side more honestly. I'm still a lot more confident hopping onto things in the direction of my lead foot, but over a tape both methods are pretty even. One thing I can't seem to sort out is leveling the bike at the top of the hop (the dreaded tuck )- my front wheel is always about a foot higher than the back, so that's height I'm losing out on...

Counting turns on the adjusters or setting them to a constant datum is awkward given the bolts will be squashed into a very small rear triangle - setting initial matching positions on both sides would be annoying too. Very true on the resolution improvement from comparing graduations on the frame to counting turns though. A vernier arrangement moving with the axle to match graduations on the frame would allow the setting of a datum for wheel alignment, though it may run the risk of showing up just how badly aligned a lot of trials frames are... It's really a case of setting the wheel up to look straight with the disk aligned to this position and then just making the same tension adjustment each side to maintain alignment as the chain wears.

The graduations are more for making sure the angle of the hub relative to a disk is constant after the wheel is moved, should stop all that nasty squealing that goes on when the caliper is off line...

The screw tensioners probably need to be coupled with graduations on the frame to allow the hub to be kept straight, but look like a nice solution (Road bikes from back before vertical dropouts were common used this setup, but chain tensions were nothing like on a trials bike). Probably not as quick as snail cams for wheel removal or setting tension, but you'll get more tension. Depending on the hub you run and how they finish the screw tensioner end, the axle could get damaged by the end of the screw tensioner... I'd love to see a standard mounting point for a tensioner on trials frames (That's not the derailleur hanger). I like the setup on my Echo fixed hub though (Which needs no extra mounting point at all) - very robust and quick to adjust without getting in the way, though I haven't landed on it yet, so can't be 100% certain how touch it is ...

I got 6 months out of a 2.5" Minion dual ply super tacky - fantastic grip, no pinch flats and the 6 month durability wasn't too bad either... Probably the best compromise between grip and longevity for me anyway...

My comment on the geometry change was about the big change when you fit a new chain/different gear - I would definitely be very surprised if you noticed individual adjustments to maintain tension alright. If the cams are in the same position both sides (And the frame is straight/cams aren't deformed etc) the disk should run straight in the caliper, but that's not what I'm talking about - I'm talking about the disk pads no longer sitting centered on the braking surface of the disk as the wheel is moved around in the dropout... Out of curiosity, has any manufacturer tried an eccentric BB with vertical dropouts in a trials frame? It would allow for perfect rear wheel alignment and easy wheel removal, while the nature of the eccentric adjustment would keep the chainline etc. straight. It would tweak the BB rise and chainstay length/reach rather than the chainstay length though. Since there are two solutions for almost all chain tensions (Except BB fully forward or backwards) there would be a high and a low BB option for the setup... Pretty sure it'd weigh more than a tensioner or snail cams though...

I haven't owned a bike with them, but I've tensioned enough horizontal dropout bikes with and without chain tugs of various descriptions to never want to endure them on my own bike. You haven't addressed the other comments though - namely the change in chainstay length inherent in adjusting chain tension by moving the wheel and the readjustment of brake pads to maintain alignment with the rim (I'm presuming you have a moving disk caliper or the brake pads don't catch the whole disk depending on where the wheel is in its adjustment range). The 74 kingz tensioners are pretty poor as evidenced by the sheer number of threads on this forum filled with bodges to make them actually work, so it's a bad comparison. Modified derailleurs and better designed tensioners work fine, while making it easier to take the wheel off, maintain correct chainstay length and keep the chain tensioned...

It'll look a bit weird on powerpro's - all the old school ones have one of the chainring bolt holes behind the crank arm rather than one on each side of the crank arm, so the gap in the guard will be visible rather than lining up with the crank arm... Having that gap visible is of course a further tribute to the oldschoolness (Probably not a real word) of the whole setup... If I have any 5 bolt cranks left I'd buy one...

In the immortal words of Gabby Johnson from Blazing Saddles: Rev'rend!!!

With vertical dropouts you've got the exact chainstay length specced in your frame's geometry rather than having to deal with a change every time you replace the chain (And gradual changes as you tension it). Snail cams seem to be a lot of trouble to adjust compared to a sprung tensioner or even the fixed one on my Echo stock hub (Which takes all of 10 seconds to adjust every 2 or 3 hard cycles), alignment of the brakes will need to be adjusted as you move the wheel around and running a disk will usually involve a bit of messing around unless you have a sliding disk mount. To be honest I'm a lot more curious as to why people are willing to endure horizontal dropouts ...