Tracking a bicycle...

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Firelite

Forager
Feb 25, 2010
188
1
bedfordshire
Bearbait deserves a mention in dispatches too, for the observation about greater variance from the average line of travel when going uphill, because of wobbling more. Nice one.
 

awarner

Full Member
Apr 14, 2012
487
4
Southampton, Hampshire
Bikes are a bloody nuisance and not allowed in my woods due to SPA, SSSI, SAC etc (it's one of the smallest NT sites in Hampshire but has the most scientific designations) as well as the paths are not designed for it but still get them coming through.
It's not even kids it's the more mid life crisis late 30's-40+ that believe any signage does not apply to them. (rant over)

Back on topic, tracking bike travel I've found can be a bit hit and miss but generally I look at slopes and skids etc but as it's a wet woodland site I look after, some of the furrows they create are hard to identify travel because of the viscosity of the mud this time of year.
 

nic a char

Settler
Dec 23, 2014
591
1
scotland
"Bikes are a bloody nuisance"
Yes on our paths it's a mixed bag - many don't bother with bells or any other warnings, some make pedestrians jump aside or even ride into them, while some are courteous & considerate.
 

MilkTheFrog

Tenderfoot
Nov 10, 2015
55
0
United Kingdom
For direction of travel, if you can find a hill then tracks with a lot of front wheel swerving probably mean that the bike was going uphill, but straighter tracks probably mean that the bike was going downhill. The natural response to putting out a lot of effort while climbing is to pull on the handlebars, which better cyclists will do less as it wastes energy.
 
Feb 21, 2016
6
0
Birmingham
Many people will stand on their peddles when cycling uphill, which will shift the cyclist's weight forward. More experienced cyclists will not do this as much as whilst standing can help give more power when pedalling, it is more efficient to keep your centre of gravity over the rear wheel.
 
Mar 15, 2011
1,118
7
on the heather
I managed to get an hours dirt time today.
So as to some observations concerning the Q above , as for direction of travel, pointers where the most obvious sign of direction, branches, twigs and small plants getting caught up in the wheel and pushed over and compressed in to the ground, leaving small impressions indicating the direction of travel, another clear sign was roots being pushed in the direction of travel then springing back to their original position and leaving a void, some stones in the track left a similar void.
Ill post up some images I got which I think might help illustrate the point a bit better than my clumsy ramblings.

Looking straight down at twig from above, bike travelling from left to right. "I scratched out the imprint of the twig a bit to make it a little clearer for the picture".



Same as above, twig pushed over in the direction of travel.


Close-up of stone compressed in to ground leaving a small void behind to the rear , bike travelling from bottom to top of image.


On moss, not quiet as clear here but twig impression still visible, bike moving from bottom to top of image

Same image but with lolly pop stick in the impression


Root rebound leaving a void after bike passing form right to left



An old image of some sand transfer in a sand trap/spoor pit .
 
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Firelite

Forager
Feb 25, 2010
188
1
bedfordshire
Great, 21st Century Pict - that is really nice, empirical stuff.
Does this mean that the trackers have beaten Sir Arthur Conan-Doyle (trading as Sherlock Holmes) in a fair fight? If so, then I think that is quite impressive!
 

pieinthesky

Forager
Jun 29, 2014
138
39
Northants
"To initiate a left turn you first have to push the handlebars to the right"
not necessarily

Too lean the bike to the left, you turn the bars to the right to move the bike out from underneath you. Once you are leaning (toppling) to the left you then turn the bars to the left to keep the bike underneath you so you don't fall over.

This is something we all do naturally without even realising. Try it, ride in a straight line and very gently turn the bars and see which way you end up going.
 

mrcharly

Bushcrafter (boy, I've got a lot to say!)
Jan 25, 2011
3,246
33
North Yorkshire, UK
Too lean the bike to the left, you turn the bars to the right to move the bike out from underneath you. Once you are leaning (toppling) to the left you then turn the bars to the left to keep the bike underneath you so you don't fall over.

This is something we all do naturally without even realising. Try it, ride in a straight line and very gently turn the bars and see which way you end up going.
I've done a *vast* amount of cycling and believe me you don't need to move the bars to the right in order to lean the bike left - you can just push the bike left (when out of the saddle). It's also possible to come to a complete halt, turn the bars in one direction, then set up (without putting a foot down).
 
Mar 15, 2011
1,118
7
on the heather
Hi again, I was on the back foot the first time out the other week looking at bike tracks and trying to workout the direction of travel, so from the picture below, here's a couple of things I missed the first time.
As the cyclist "travelling from left to right" dismounted "right hand side?" relevant:dunno: he or she ?, "I didn't follow the footprints leaving to and returning from the probable p**s spot" "see second Image, top left corner here" he or she picked up the bike very sightly and across a few inches to lean it up against the tree, ["as Bishop pointed out earlier" so on the ground we have the bikes wheelbase measurement, annoyingly, had I had a closer look at the tree for top sign and found where the saddle had rested against the tree, from this measurement it should be possible to estimate the riders approximate hight.
Another wee bit of information we can gather on the description of bike is, given a favourable piece of ground and some tread damage or with some clear transfer sign "see bottom image" it should also be easy enough to work out the wheel size from the tire circumference.




top left 2 footprints, there and back again, or a /, a wee moment ;)


Wheel size from transfer.
 
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Firelite

Forager
Feb 25, 2010
188
1
bedfordshire
Sterling Stuff 21CP. Just one query. Did you set this up to see what it looked like, or did you happen across the scene as found? My reason for asking is that it looked to me a bit more like the bike came in from the right and went off towards the left of the image. Clearly, if you set it up you would know, and I absolutely accept that you saw it 'in the flesh' as it were.

Even so, the overall pattern together with the fact that we are habituated to get on and off our bikes on the left side rather than whilst standing in the road, tends to suggest a right to left dynamic. Also, rather than leaning the saddle against the tree, would the distance between the tyre track and the tree be similar to half a handlebar? Then when the rider returned, they could just have lifted the front of the bike to set the direction of intended travel, and the rrar tyre followed across the image in the foreground. Have I got this wrong, please? Are you just testing?:confused:
 
Mar 15, 2011
1,118
7
on the heather
Sterling Stuff 21CP. Just one query. Did you set this up to see what it looked like, or did you happen across the scene as found? My reason for asking is that it looked to me a bit more like the bike came in from the right and went off towards the left of the image. Clearly, if you set it up you would know, and I absolutely accept that you saw it 'in the flesh' as it were.

Even so, the overall pattern together with the fact that we are habituated to get on and off our bikes on the left side rather than whilst standing in the road, tends to suggest a right to left dynamic. Also, rather than leaning the saddle against the tree, would the distance between the tyre track and the tree be similar to half a handlebar? Then when the rider returned, they could just have lifted the front of the bike to set the direction of intended travel, and the rrar tyre followed across the image in the foreground. Have I got this wrong, please? Are you just testing?:confused:

Hi Firelite
Not my bike, so the scene is as I found it.
You could very well be right about the direction of travel, "the image below" of the snapped twigs is a bit confusing, the very smallest snapped off top twigs look and suggests to me of movement from left to right but as you can see from the images in the post above there is a lot of foot disturbance in the area and the larger branch looks to have been dragged to the left.
One other thing that suggested to me travel was from left to right was the overall picture and the position of the tracks, this is at a crossroads with only one road heading through a forest, the other 3 main road being quite busy and open, so to me it looks like someone has turned off the main road and on entering the forest road immediately done a 90 degree turn in to the wood for a P*#s then continuing on with their journey down the forested road but with a much longer meandering track heading back to the metalled road, a sort of a 7 shape off and back on to the road.
Truth be told I can only give myself a 50%+ chance off being right on this one so your interpretation could easily be the right one dude.

.
 
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Firelite

Forager
Feb 25, 2010
188
1
bedfordshire
OK, thanks 21CP, its an interesting one to ponder. Either way, thanks for taking the time to post the pics, top job.:You_Rock_ I'll think about it a bit more and get back once I've thunk.
 

Firelite

Forager
Feb 25, 2010
188
1
bedfordshire
OK, I have thunk. This is my offering for what I think has happened in the first image offered in 21CP's excellent snow tracks pictures above. With reference to the top picture, I am relying on the principles outlined in the article linked from my earlier post. In essence, the article uses the fact that the rear wheel, being set into the frame of the bike, can only ever point towards the axle of the front wheel, which must always lie immediately above the position where the front wheel touches the ground. The front wheel is free to move, but wherever it does move, the rear wheel must be one wheel base (the distance between the axles) away from it and it must always point towards the front wheel, too. So, how do we know which way the back wheel is pointing from a curved track? Well, we take a tangent to the curve, that is, a short straight line that just touches the curve at one point. At that point, the straight line will point in two directions, and it will generally be hard to know which is the direction of travel and which is the direction the bike has come from. Even so, sometimes it will be possible to see that one direction of the tangent cannot be the direction of travel, because it doesn't point to the front wheel, because there is no front wheel track along that half of the tangent.

From this it follows that the other direction is where the front wheel is, and this orients the bike in the tracks. Here's the thing: In the picture with the tree, above, consider the pair of tyre marks on the left of the image. Lets assume that the bike was coming in from the left. One of the tracks reaches an end, but the other carries on past around a curve. Because the rear wheel always points towards the front wheel, the point where the tyre mark stops should allow us to extend a line straight on from that point to coincide with the front wheel. But it doesn't.

Further more, given the slight curve of the pair of tracks on the left, if they had been made by a bike travelling left to right, then the mark on the outside of the curve should be the front tyre. However, it clearly isn't because the other track overtakes it! Therefore there are at least two inconsistencies with the proposition that the bike travels left to right.

OK, lets try it the other way round. The tracks can accommodate a bike coming in from the right and stopping, with the front wheel near the tree. We might even suppose that the right hand handle bar is leaning against the tree. At this time the rear wheel is in the 'stop' point to the right of the tree. That means the back of the bike is sticking out to the right a bit. That could account for why the footprints go so far to the right of the tree, otherwise the rider would walk into the bike. The rider comes back from his short walk, approaches the left side of the bike (as per habit for a cyclist in a country where they ride on the left), picks up the bike by the handlebars to set the front wheels in the direction of the left of the picture, then steers away, with the rear wheel completing the sweep across on the inside of the front wheel's line (ie on a smaller radius of curvature), all consistent with the mechanics of the bike, and with the rear wheel always pointing at the front wheel.

Sound reasonable?
 

General Strike

Forager
May 22, 2013
132
0
United Kingdom
Thanks! A pity everything else I wrote was so far off the mark! I just ran across another link explaining the same method of determination as per your link, and it is wonderful in its simplicity. The rear wheel is fixed relative to the bike frame, and the distance between the two wheels is fixed too. Brilliant.
 

General Strike

Forager
May 22, 2013
132
0
United Kingdom
We could test your theory if we had a carpark no-one really cared about and a big tray of white paint... I think that in normal riding, basic physics would preclude turning left without a small right 'swerve' - just in some cases it will be tiny. It *might* be possible to avoid the swerve by leaning your body and the bike over until it starts to fall to the side, then turning the front wheel in the direction of the fall to 'catch' yourself - but it would feel very uncontrolled and sketchy. You may be right about the idea of stopping, turning the front wheel, and then starting, though.
 

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