VincentHill
Needs a life
Posts: 6520
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posted September 07, 2002 12:10 PM
Mike my .02 is that the 2 case covers are an excellent idea and my feeling is that this will stop 50% of the problems in riding away from a fall over! My Idea is to mount one on each side of the frame near the swing arm pivot (Drill and tap a hole on each side and screw a slider with a large base! In just a "0" Speed tip over, the foot peg Brackets just "SNAP" Off! Very hard to ride with no shifter of foot peg! I even thought about running a steel rod through the swing arm pivot and mounting a slider on each side sticking out far enough to protect the covers and the peggs! I looked at mounting a tube to the top front engine mounts and sliders on both sides there, but could not decide on how strong to make this bar because it had to be weaker than the mounts! My last thought was to make a large spacer out of tire wall! (Like exhaust Hangers) and then mount the slider on the fairing The spacer would be about 2 to 3 inches in diameter with the bracket coming through the spacer (Support the fairing and use a large 10 MM Bolt to mount the slider)! I never liked any of these ideas except the threaded hole in the frame and using a steel bolt that would strip out the threads when the slider was over stressed! Once done, then use a time Cert and then a Big Cert to repair the hole 3 times! Hopefully no one would need this "4" Times!!
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Made History @ Daytona and still one fast old man!!
  
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MikeM
Novice Class
Posts: 49
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posted September 09, 2002 12:35 PM
Freek,
I work in the railway industry where frangiable or one shot devices are used extensivley (mainly for inter coach couplings) and know from experience that it is very difficult to model and predict how a frangiable mount will behave under load. Unless the forces are all imposed along a known axis, such as being dropped vertically, then the range of variables you would have to take into account is substantial. Get it wrong either way.... too low a breaking force required and the energy of the impact will not have been dissipated before the component you are trying to protect recieves the residual, too high a breaking force required and no energy will have been dissipated again putting forces into a component in a manner for which it is not designed. I am involved in the enquiry into a recent rail crash in the UK and one of the areas we are investigating, not directly related to the crash but to the survivability of the train post crash, is why a design of frangiable mount for an inter car connector (which is used on over 2000 coaches and has had hundreds of thousands spent on R+D) failed to separate ?
Very tricky field and if you get it wrong very expensive.
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frEEk
Administrator
ummm... yeah
Posts: 9660
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posted September 09, 2002 01:50 PM
damn, does everyone here have an interesting job but me? i love trains. never really get to play w them, but it'd be one of my favourite industries to work in. anyhow, i hear ya. thats one nice thing about my industry (programming). when u get it wrong, the worst that generally happens is someone loses a weeks worth of work. not a good thing to hae happen, but not the end of the world either.
one thought tho. since we are fortunate enough to be working with a compression failure and not a tensile failure, and since the failure doesnt have to be complete (ie it doesnt actually have to break the mount entirely), can one use a progressive strength mount? one where the crush structure progressively fails like a progressive auto spring, with a non-failing centre pin to keep everything from falling apart entirely. i imagine the easiest thing would be to use something similar to the aforementioned fairing brackets, but designed such that they only fail along the slider's centre axis so the slider doesnt just bend.
mmmmm....trains...
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VincentHill
Needs a life
Posts: 6520
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posted September 09, 2002 02:07 PM
My limitation in knowledge was building a mild steel tubing extension for the frame on my Z1-R Race Bike and mounting the Oil cooler in the tail section surounded by Chromolly Steel! The Only rear mounted Oil Cooler to pass AMA Tech because the subframe would bend and not break, ant the Chromolly would protect the cooler! This is a lot more difficult than this was because the "Force" can come in so many different directions and can end up doing more damage than nothing at all!
I would settle for the harden covers and a mallable mount for the foot pegs! one that takes some force to bend before it breaks! (To Strong abd you break the frame tabs! Too weak and standing on the pegs will bend the brackets)
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Made History @ Daytona and still one fast old man!!
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frEEk
Administrator
ummm... yeah
Posts: 9660
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posted September 09, 2002 06:06 PM
i'm kinda curious as to why everyone's stock pegs break off when they'r on a hinge. seems they always break at the same spot too (not surprisingly).
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VincentHill
Needs a life
Posts: 6520
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posted September 09, 2002 06:55 PM
quote:
i'm kinda curious as to why everyone's stock pegs break off when they'r on a hinge. seems they always break at the same spot too (not surprisingly).
Good thought! Must be that they still stick out too far when folded!
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Made History @ Daytona and still one fast old man!!
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MikeM
Novice Class
Posts: 49
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posted September 10, 2002 11:35 AM
Freek
I on the other hand never had any ambitions to enter the railway industry, ended up working for a rolling stock manufacturer after doing my apprenticship in the Royal Electrical and Mechanical Engineers and getting sand blown up my ass in '90/91. The railway industry in the UK is becoming more and more regulated and controlled, on the rolling stock and operating side at least, and is taking it's lead from the aircraft industry.
I now spend about 75% of my time creating, reviewing, auditing etc. processes and standards. The other 45% (engineering joke...... I'm laughing on the inside!)is spent reviewing how other people have actually got to do some real hands on engineering and waht they did wrong!!!
I miss the hands on stuff and am thinking of a move away from the industry, possibly into fibreglass and composites with a local company.
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MikeM
Novice Class
Posts: 49
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posted September 10, 2002 11:50 AM
But back to the subject in hand...... Had a thought. Back in the late '80's there was a mountain bike "suspension" bit of kit called a "flex-stem". This used elastomers as a springing and damping medium, and to fine tune it we used to use skateboard truck rubbers which were, and I assume still are, available in different durometer ratings.
If you made the frame/engine side of the mount as a cup shape with the internal bore large enough to allow a skateboard truck rubber to fit down, and expand when compressed, and then made the slider side of the mount as a plug which was a sliding fit down the bore of the cup. With a hole down the centre line of all 3 items (already in the rubber) for, say, an M10 bolt shank you could make a reasonably compact and possibly tunable force absorber. You could counter any non parallel forces by having as much over lap as possible between cup and plug, the only immediate problem that springs to mind is stiction between cup and plug on perpendicualr forces being applied... maybe make the plug as one piece with the slider, if you made the slider/plug from Cast Nylon 6 (as the majority of other slider are, tip: must be impregnated black as this is the only cast nylon colour which does not suffer from material degredation if exposed to UV radiation i.e. sunlight)and go for a high finish machined surface this might be overcome.
Thoughts?
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MikeM
Novice Class
Posts: 49
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posted September 10, 2002 11:50 AM
But back to the subject in hand...... Had a thought. Back in the late '80's there was a mountain bike "suspension" bit of kit called a "flex-stem". This used elastomers as a springing and damping medium, and to fine tune it we used to use skateboard truck rubbers which were, and I assume still are, available in different durometer ratings.
If you made the frame/engine side of the mount as a cup shape with the internal bore large enough to allow a skateboard truck rubber to fit down, and expand when compressed, and then made the slider side of the mount as a plug which was a sliding fit down the bore of the cup. With a hole down the centre line of all 3 items (already in the rubber) for, say, an M10 bolt shank you could make a reasonably compact and possibly tunable force absorber. You could counter any non parallel forces by having as much over lap as possible between cup and plug, the only immediate problem that springs to mind is stiction between cup and plug on perpendicualr forces being applied... maybe make the plug as one piece with the slider, if you made the slider/plug from Cast Nylon 6 (as the majority of other slider are, tip: must be impregnated black as this is the only cast nylon colour which does not suffer from material degredation if exposed to UV radiation i.e. sunlight)and go for a high finish machined surface this might be overcome.
Thoughts?
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frEEk
Administrator
ummm... yeah
Posts: 9660
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posted September 10, 2002 01:34 PM
i know what u mean about hands on. i'v squandered my EE degree on computer programming. i hate the lack of tangible results. i can imagine doing proceedures & standards would be similar, altho the process of engineering processes & standards could b interesting in that u prolly get rather theoretical, and spend most of ur time looking for "if"'s and exceptions to each rule. thats prolly my stongest point & i do enjoy that some.
re the slider, yeah, thats kinda what i'm thinking. i remember reading that more modern mountain bike front forks were often using the same polymer inserts as it is a less expensive, more rugged, and easily tunable design. the only thing that put me off that thought to begin with is of course it will have a significant amoutn of spring action and thus will return the absorbed impact, albeit at a lower force. hence the talk about an energy absorbing crushible structure.
the one change i think i would make to ur suggestion is to lose the cup, and go with a sleeve for the bolt instead. i'm assuming the reason for the cup was to provide lateral strength, which would be supplied by a sleeve too. however, a sleeve for the bolt (on the inside of the polymer donut, or even on the inside of the frame) would not have the issues with leaving room for expansion of the donut. however, the smaller diameter of the sleeve would likely mean les strength, and a longer overall product. actually, the more i think about it the less i like it. perhaps a cup like u said is best, but a cup that is narrower on the top where it goes beyond the donut and means the shaft of the slider. this way there is no lateral play but u still have expansion room. better yet, just make the shaft that much wider than the donut so the cup/outer sleeve doesnt have to be tapered.
ah, i'm not used to actually thinking anymore. my head hurts.
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