Any question answered...

Anyone know if Shimano STX and STX RC have the same pull ratios?
I can never figure out si shimano

Some places refer to them as Dual Drive

£6.66

_\m/

amazing! Thanks

Think there is a Brexit march or summat tomorrow.

Yeah, up to 9 speed Shimano MTB all plays nicely.

Does sound like fun but I'm marching home tomorrow, mainly just riding round and drinking beers at tourist places today, quite enjoying it.

I know I should buy one, and I will, but does anyone know of a link to free Ordnance Survey maps online?
Cheers.

https://www.bing.com/maps - you can choose OS as a view mode

I can get you a region as a PDF if you like. Tell me A4 - A0, whereabouts you want it and 1:50 or 1:25 and I'll send it to you in a PM.

obviously a 1:25 A4 map is a very small area so bear that in mind.

obviously a 1:25 A4 map is a very small area

Yes, about 5m by about 7.5m...

Cheers! It's for the OS leisure map of the Pentland Hills

If you only want the map briefly, Viewranger has a 7 day free trial.

don't tell everyone about this site: https://wtp2.appspot.com/wheresthepath.htm

Ya wee beauty. Cheers for all the feedback!

If I want to approximate a circle of a given diameter (D) using planks of a known width (W), then I can work out how many planks I will need (D/W), but is there a way of calculating the length of each plank? The middle plank length equals D, but how much does each subsequent plank reduce by?

only showing half the planks for brevity

1 Attachment

Maybe the easiest is to draw a 1/4 circle onto graph paper with a compass and then take readings along the top edge where each plank would start/end and double the distances.

I could draw it out, but was hoping there was a formula like if plank number is 1 (the middle one) then length = diameter, if plank number is 2 then L = diameter - 2% etc

Equation of a circle centred on the origin is x^2 + y^2 = r^2.
You're looking for the values of 2y as x takes the values W/2, W+W/2, 2W+W/2,... right?

NB. I assumed you wanted the corners of the first (longest) plank touching the circle, rather than the midline touching the circle and the corners sticking out a bit. If that's wrong just use x=0 for the first plank, x=W for the second, etc.

um....... right. maybe!

edit, I dont really understand any of your message :)

I think I'd like the midline to touch the circle. Would an example help? My planks are 30cm wide and I want to make a circle of 240cm diameter, so 9 planks in total (7 full planks wide, with two half planks at each edge). P1 = 270cm 240cm, P2 =?

No trouble - the formula just tells you the relationship between the x & y coordinates of a point on the circumference. We can just look at the top-right bit as Clockwise said, and stick to positive x & y (it's simpler if we just say the origin 0,0 is in the centre of the circle).

So, x is the sideways distance from the centre of the circle, to the middle of the plank we want to measure.
That leaves y as the height of the top of the plank above the middle of the circle. We actually want 2y in the end, because there's the same length below the centre as above, but solving the equation for y is how we get there.

OK, so D=240, and r=120 (since this formula uses radius instead of diameter).
I assume that means the centre plank should be 240 long?

If so, the next plank to the right has x=30 (the centreline is 30cm right of the middle of the circle), and

           x^2 + y^2 = r^2
becomes   30^2 + y^2 = 120^2
                   y = √(120^2 - 30^2)

and then we repeat the whole thing for x=60 for the second plank, etc.

plank#   x        y        height
0        0        120      240
1        30       116      232
2        60       104      208
3        90       79       159

So you'd have one plank #0 in the centre, 2 of plank #1 (just right and left of the centre), etc.

You can work out the total length of the planks if you work out the area of the circle using the diameter, then divide that (using the same units) by the width of the planks to work out the length of the planks. There will be a slight error as the area of the circle ouside the midpoint of each plan will be slightly more than the area by which the plank overlaps the edge of the circle, but it'll be close.

To calculate the length of each you'd need to use @useless 's formula, which of course is really just the Pythagoras equation used in relation to a notional triangle with its point on the circumference of the circle. r^2 will remain constant - just plug in the right number - and X(1) will be half the width of a plank (W/2), and each remaining figure for X will be W/2 + another W.

Edit: damn, too slow. What he said ^.

thanks both of you, and clockwise for the sketching suggestion which is what i have reverted to to clarify what i actually want

i will build a little .xls to plug various parameters into

Knowledgeable lfgss, a question concerning straight steerer suspension forks for a Marin Pine Mountain 2016.
Being a 27.5+ is it better to get a 29er fork (8mm diameter difference) e.g:
big bouncy

or try my luck with a 27.5 fork and the associated clearance issues sure to follow, e.g:
not so big bouncy

Handlebar mounted umbrella for turbo training outdoors vs garden parasol?
Garden parasol would probably pop over the fence when/if windy. Really only need a bit of cover to keep sort of dry for about an hour. Don't want a massive sail. Understand that in asking "umbrella, outdoors" sort of ignores the "umbrella in wind = sail"