|   speed of drop affect bike/body impact. Scientific reasons??? | jimbobb
Jan 3, 2002 12:00 PM | | I would like to know whether the speed of landing a drop makes a difference to the actual impact, provided the technique of the drop is the same.
Lke for example if yu did a 6 foot drop, down to the ground, with brakes fully locked and no horizontal motion, compared to the same drop but travelling at say, 30mph. (backwheel first)
Would there be a difference in the impact of the drop, is there a difference in the force acting on the bike/body on impact?
In conclusion, which would be the less stressful way to drop on the bike/rider?
Would this apply to all variations of sizes of drops? 4ft-20ft |
| re: speed of drop affect bike/body impact. Scientific reasons??? | Tommot
Jan 3, 2002 1:29 PM | | well, scientifically, you will hit the ground at the same velocity (downwards), however fast you are going forwards, having spednt exactly the same amount of time in the air.
the problem is that it is much easier to absorb the drop by landing back wheel first, with your brakes on, which you obvoiusly cant do at speed.
if you did just land it, with a lot of speed, the extra speed would give you more balance, so it would possibly make you feel like you landed it softer, but u didnt.
so scientifically it makes no difference, and the totally different techniques are to blame for any differences. |
| depends on the landing | blong
Jan 3, 2002 2:35 PM | | from a physics point of view, if you land on to flat, your speed doesn't matter. if you land on a downslope, your speed does matter. in theory, if your velocity is fast enough (or the downslope is steep enough) for you velocity where you land to be in the same direction as the downslope, you will have a perfectly smooth landing.
conversly, if you're landing on an upslope, you better not be going fast!
but that's just simple physics. it's easier to land nicely on the rear wheel if you land with the rear brake locked up. |
| re: speed of drop affect bike/body impact. Scientific reasons??? | Regder
Jan 3, 2002 3:53 PM | | my disclaimer as always, I am in no way an engineer or physics guru so this could be 100% wrong.
Lets do a hypothetical scenario, you do a 6 foot "huck" going at 5mph and land perfectly flat, then you do same "huck" going at 30mph this time landing in the exact same manner, which do you think will be smoother? The latter of course. When travelling at a higher speed your momentum is more forward, rather than straight downwards as it would be had you been going significantly slower. Thus your body/bike has a lot less force to absorb than had you been travelling straight down. Take a gander at Bender, a lot of his drops that you see on video have very little speed in them, however when the same drop is done with some speed behind it, it is much easier for him to land it (i.e. not get tossed over his handlebars).
Doing the same 6 foot drop via the trialsin method is completely different. The main advantage of the trialsin method is that you are better able to absorb the drop (momentum). Take a look at a trials rider do a six foot drop, if he's good enough you won't hear a sound even though his momentum is going straight downwards. Due to the manner in which he did the drop, he is better able to absorb the momentum throughout his bike/body.
Certain trials riders have dropped over 10 feet without incurring any damage whatsoever to their bike or body, easily showing the advantages.
However the trials method is limited in height. Since most trials riders run zero rear suspension they are limited in how much force they would be able to sustain before the rider/bike broke. Suspension wouldn't help matters much, possibly throwing the riders balance off, preventing him from absorbing the drop as well as he might be able to otherwise. |
| re: speed of drop affect bike/body impact. Scientific reasons??? | ryan0
Jan 3, 2002 6:44 PM | | I also want to say that I have only a fundamental understanding of physics, but I think thats all this needs so...
Regder, When you say "huck" you mean a downhill landing yeah?
Because to flat like somone else said it really doesnt matter how fast youre moving- Ok, unless youre going so fast the curvature of the earth is your downhill- your horizontal and vetical inertias are separate.
But as to your question, it seems like concensus that it makes no difference your speed because of the above but further that the technique will change.
In the at speed technique you will need to know how to manual pretty well if you want to mimic the static landing.
If you could do that- land in a manual that perfectly matches your static landing- you would feel exactly the same impact- and it would look really cool at 30 mph.
what do bugs think about? |
| Actually.... | OrBust
Jan 3, 2002 7:49 PM | | Actually...your horizontal velocity is completely independent of vertical velocity. If you hit a 6 foot drop doing 200mph, or .5 mph you land with the exact same impact. An example of this, although some assumptions are made(neglecting air resistance, and curvature of earth)....is if you were to hold a gun 2 feet above the ground and fire a round, and at the EXACT same time you fired the round you dropped a bullit to the ground in front of you from the same 2 foot height....the dropped bullit will hit the ground at the EXACT same time as the fired round.
Ive thought about the forward momentum drop vs. no momentum drop before, and I think that with some speed it makes it easier. Although with good technique trials bikes are super easy to cush in to. But I think its more rider position, and how the body is on landings. On a freeride bike, your so far back(compared to a trials bike) that if you try to land trials style from a drop you cant get the bike vertical enough and into the correct 'trials' position. But when you bust the drop with some speed its much easier to land....you kinda land in a 'manual', and you actually travel forward on your rear wheel before your front touches down...instead of 'slapping' your front end down if you try to trials it in.
A good example of this is my buddy, he can straight up land a 4 foot drop and only compress his Z5's like 3/4 of an inch when he has some speed....he actually lands in a kinda a manual, and rides it out for a split second. But when it comes to slower trials style drops, he slaps the front harder...he cant get the bike vertical enough in the air since it has a short stem and laid back geometry. Downhill bikes are even worse, your SO far back. I was able to cush my hardtail freeride bike off a 6 foot drop to flat WAY smoother then I could my bullit with monsters on it. |
| Actually.... | ryan~
Jan 3, 2002 10:04 PM | | separate, independent... |
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