Lug Wrench

[Kiwi_Roy]

I'm sure I'm not the only one faced with this dilemma, what tool to take on a trip in case you have to remove a wheel nut on the roadside, a regular wrench for a 27mm nut is huge, here's  what I did.

Measure the length of a flat with a compass

The flat just happens to be exactly the radius of the nuts circle.
So without moving the compass scribe a circle on a scrap of metal

The radius also happens to go exactly 6 times into the circumference.
So divide the circle up by 6

And carved a simple wrench of 1/8" Aluminum using a regular wood coping saw, elapsed time < 60 minutes.

I made it short as I can always find a rock to use as a hammer. The aluminum is plenty strong enough for this task and it takes up little room in the tool box.

[ridingron]

And then?

[Sasquatch Jim]

 So what did you do then?  Cut yourself a wrench out of a scrap of steel?

[Kiwi_Roy]

Just be patient, i'm going as fast as photobucket will jet me 

[Phang]

I think, knowing the radius of the nut won't tell you the size of the socket, need a little calculations 

[oldbike54]

I think, knowing the radius of the nut won't tell you the size of the socket, need a little calculations 

 So then the answer is blue ?

 Dusty

[Phang]

So then the answer is blue ?

 Dusty

depending on which scientific calculator you used 

[Kiwi_Roy]

No but no measuring stick was harmed in the process 
Just measure across the flats for the socket size.

[oldbike54]

depending on which scientific calculator you used 

 Plugging the data into one calculator gave me the answer of Clarinet , but I'm pretty sure that isn't correct 

 Dusty

[Phang]

No but no measuring stick was harmed in the process 
Just measure across the flats for the socket size.

Very clever way of drawing a perfect hexagon 

[Phang]

Plugging the data into one calculator gave me the answer of Clarinet , but I'm pretty sure that isn't correct 

 Dusty

it hasn't been moisturised for a year, I hope the wood didn't crack

[oldbike54]

it hasn't been moisturised for a year, I hope the wood didn't crack

 I'm guessing this will confuse almost everyone else 

 Dusty

[Moto]

This is the best tip in ages! I am impressed by the geometric construction and by the use of a coping saw (!) to make a useful tool. I don't know which is more delightful.

Makes me proud to be a Wildguzzi member.

Moto

[tris]

Well Apotherm is a new word to me ..... Wildguzzi is so educational 

Posed with the same problem, I planned to go down the route of a monster 27AF combination spanner and an angle grinder to chop it to a suitable length and then use a suitable rock to "persuade" it

However I ultimately solved the problem by flogging the Cali and buying the Breva - but still have the giant combi spanner lying around as I didn't get as far as chopping it up

[Phang]

out of curiocity, I calculated the radius/side length of a 27mm nut.

It's 15.5884572681mm 

[charlie b]

I still have the factory wrenches for my T5.  One of them is a double box wrench.  One end is 27mm for the axles.  The other is 22mm for the dipstick and fill plugs.  It's about 7" long and seems to be well forged steel.  A bit rough but it works well.

[Antietam Classic Cycle]

I still have the factory wrenches for my T5.  One of them is a double box wrench.  One end is 27mm for the axles.  The other is 22mm for the dipstick and fill plugs.  It's about 7" long and seems to be well forged steel.  A bit rough but it works well.

This ^^ The original Guzzi "dog bone" wrench is what I carry.

[Moto]

I think, knowing the radius of the nut won't tell you the size of the socket, need a little calculations 

You can see by inspection that the ratio of the apotherm to the side in this case is sqrt(3)/2, remembering the Pythagorean theorem, and you can find the numerical answer in your head if you know the square root of three, which is about 1.73.

To see this, consider the length labeled "side" to be 2 units. Then either of the right triangles in the shaded area has an hypotenuse of C = 2 units (the radius of the original circle) and another side A of 1 unit. Since A^2 + B^2 = C^2, the remaining side, B, the apotherm, is B = sqrt(C^2 - A^2) = sqrt(4 - 1) = sqrt(3) units. The ratio of the apotherm to the "side" in the diagram, then, is sqrt(3)/2, which you could calculate in your head as 1.73/2 = .865, on a good day. The calculator value is sqrt(3)/2 = .866025.

Phang's formula gives the same result, of course. (I never heard of an apotherm, either.)

But Roy's Euclidean construction, with no numerical calculations, takes the cake, since there is no need to know the size of the resulting wrench. Kudos.

[Moto]

out of curiocity, I calculated the radius/side length of a 27mm nut.

It's 15.5884572681mm 

= (27/2) * [2/sqrt(3)] = 27/sqrt(3)

The general rule, then, is hex size = sqrt(3) times flat length.

[LowRyter]

Wow,

I'd really like to see the how you made a center stand. 

[Two Checks]

Phang's formula...wasn't he Phyliss Diller's husband?

[Phang]

= (27/2) * [2/sqrt(3)] = 27/sqrt(3)

The general rule, then, is hex size = sqrt(3) times flat length.

You are good   

Are you a maths teacher?

I tried the trigonometry approach earlier today but googled the above formula for polygons.



not sure if I got it right, left school many years ago.

[Sasquatch Jim]

  This stuff is beyond my photoaprehension.

[Moto]

You are good   

Are you a maths teacher?

No, I'm a sociologist.

I know very little math, believe me. Thanks for your kind words.

Moto

P.S. Your trig formula is right.

[OlDogface]

I just laid the nut on a piece of steel and scratched its shape with a nail. Then drilled a hole near one inside edge and cut the rest out with a jigsaw. 

[Cam3512]

This ^^ The original Guzzi "dog bone" wrench is what I carry.

Me too.   And I don't have to find a rock...

[charlie b]

No rock, but, sometimes I have to kick it with my boot  :)

And mine does not look as good as Charlie's  :)

[Antietam Classic Cycle]

No rock, but, sometimes I have to kick it with my boot  :)

And mine does not look as good as Charlie's  :)

That one is actually just a photo from eBay. Mine looks even better - bought it as part of a bunch of replated stuff from Mark Etheridge, so it looks new.

charlie b: since your's is for the T5, shouldn't it be 22 mm on one end and 24 mm on the other?

[charlie b]

Charlie,

Well, I have been wrong before so it may be 24  :) For some reason I remember it being 27.  Will have to look at it next time I have the tool box out.

[leafman60]

I really admire the innovative improvisation of the Original Poster. I am not raining on his parade. However, similar already-made motorcycle wrenches are out there for those who don't want to cope with a coping saw:

http://www.ebay.com/itm/RK-Closed-End-27-mm-Wrench-for-Motorcycle-Tool-/192011133290?hash=item2cb4c1616a:g:VrIAAOSw8w1X3btV&vxp=mtr