How to weigh a bike......The weigh station is open, aw crap, closed for now.

[Tom]

Take it to the airport and weigh it at an airfreight shipper.  No charge, if you want to know how much to airfreight it .

[Wayne Orwig]

Weight each point that touches the ground. Front weight, rear wheel, and sidestand. Add them up. Block up each point that is not being weighed, so that you keep the bike level, if you want accuracy.

So yes, just add up the weights, try to keep the bike level.

And yes, there is a VERY good chance that you have a nearby grocery store that has a scale that I designed.

[Rough Edge racing]

 You all except for one or two must work for the gov't......just take something simple and complicate the simple out of it...

[Tom]

I work for the government.  . I retired from working for an airline that that did airfreight.  Guess what I use to do?

[John A]

Weigh bikes?

[Tom]

Y'ep, cars, trucks and other freight.  5000 to 6000 lb. Of papaya to  Japan.  Make the airway bill too.    Check for Hazmat req.s and paperwork per FAA regs.

[jbell]

Please let us off the hook now JBell. Were you joking from the get go ? Just put the front wheel on the scales with a piece of wood under the rear the same height, then the same for the rear. Add the two. THAT REALLY IS IT !!! If you stand on a set of scales on one foot you still weigh the same, just on both feet, each one takes half the weight, but you had me sucked in for ages as well...

No, Huzo, no joke and no sinister motives.  I was thinking you'd have to know the weight bias front/rear to calculate the one wheel at a time method.  As so often happens, I am wrong again.  I'll still have to get a 3-400# range scale but will give it a go on my bikes, enquiring minds want to know.

[Huzo]

No, Huzo, no joke and no sinister motives.  I was thinking you'd have to know the weight bias front/rear to calculate the one wheel at a time method.  As so often happens, I am wrong again.  I'll still have to get a 3-400# range scale but will give it a go on my bikes, enquiring minds want to know.

Ok then Jbell, that's a different kettle of kippers then. The two wheels are indeed taking different amounts of weight to a more or less degree, but together they still add up to the same as the total weight.

[keener]

Take it to the airport and weigh it at an airfreight shipper.  No charge, if you want to know how much to airfreight it .

thats what i have done , accurate to the ounce ...fill your tank so you get the real wet weight ...done deal 

[rodekyll]

Using the single wheel method I get 1120# with gas aboard.

[RANDM]

Is that with your gear as well RK?

I've seen Classic Racers being weighed one wheel at a time
On scales and the other wheel was being elevated.

Another option would be a Post/Parcel distribution centre, I
was a Postie when I got the 1150 and weighed it at work.

Maurie.

[rodekyll]

Nope, it's the bare trike with all fluids filled.  No luggage or me.

[Huzo]

Is that with your gear as well RK?

I've seen Classic Racers being weighed one wheel at a time
On scales and the other wheel was being elevated.

Another option would be a Post/Parcel distribution centre, I
was a Postie when I got the 1150 and weighed it at work.

Maurie.

Hope you got a mealie out of it. Was it at 2.30 mid week or 3.30 Mon/Fri ? Was also postie (35 years)

[RANDM]

Mealie??? Ah ......... No - I didn't have the priveledge of
Being wrapped in cotton wool and treated like a Princess
     Did a few years for a Contractor and then
a few as full time Casual for Aus Post, kinda rare for them
to hire Little Red Riders with Mail dying and Parcels going
Apeshit. Only really got the spot ' cause they got a new
Manager who was an Angel. All over a couple of years back.

Maurie.

[RANDM]

Nope, it's the bare trike with all fluids filled.  No luggage or me.

Wow - substantial. I figured you'd built for longevity, but
that's still a bit of a surprise.

Maurie.

[rodekyll]

Surprised me, too.  I used a gauge thicker than necessary square channel throughout the main trike section, and a cast iron differential punkin.  It is probably 200# heavier than it needs to be.  I was after a smooth ride and the ability to stick to the road in a sidewind.  That part is working out.  The unanticipated side effects are that the loaded ground clearance isn't quite what I'd hoped for, and the rear brakes don't make me happy.  I'll do better next time.   

[RANDM]

You did very well this time sport. 

Maurie.

[jbell]

Bought two $10/330# scales at WalMart.  Set them at wheelbase with 2x4's in between to fill the gap and a little ramp up to the first one.  First up, my 860GT came in at 470#.  Next, the K75RT came in at 540#, both according to spec.  When backing the K75 back down, a loud crack from the first scale and it is buggered up.  Tried to reset and compensate for the difference in a known weight (me).  850 T3 came in at 475# plus throw in another 20# for mufflers for 495#.  Not sure about this one, will get another scale and try again.  Very surprised they came in what the manuals said, expected them to weigh heavier.  First  I tried with a plank across both the scales but that produced varying results and went to tires directly on the scales. 

[Moto]

Bought two $10/330# scales at WalMart.  Set them at wheelbase with 2x4's in between to fill the gap and a little ramp up to the first one.  First up, my 860GT came in at 470#.  Next, the K75RT came in at 540#, both according to spec.  When backing the K75 back down, a loud crack from the first scale and it is buggered up.  Tried to reset and compensate for the difference in a known weight (me).  850 T3 came in at 475# plus throw in another 20# for mufflers for 495#.  Not sure about this one, will get another scale and try again.  Very surprised they came in what the manuals said, expected them to weigh heavier.  First  I tried with a plank across both the scales but that produced varying results and went to tires directly on the scales.

Hats off to you, jbell! Actual instrumentation acquired!

Now you can test theories of the importance of having both wheels on the same level, even without buying another scale to replace the broken one. I hesitated to weigh in (ha ha) when the discussions were just theoretical, but now I'll present my own theory, the Sine/Cosine Theory.

The Sine/Cosine Theory holds that physical problems of this sort can be solved by appeal to either the sine or cosine function, without any messing around with vectors or other actual mathematical analysis. The Theory says that as some relevant angle varies, the required measurement (a force, perhaps) is related either to its sine or cosine, whichever seems more appropriate.

Here is my analysis of bike weighing using the Theory. If the bike is weighed with two scales while it is on the level, the front scale (e.g.) will show weight W₁, which is usually about 50% of the total bike weight. That's the first proposition. The second proposition is that if the bike were rotated upward 90 degrees and stood on its rear wheel pointing straight up in the air, the weight on the front wheel's scale (if it could be positioned under the wheel) would be zero.

Now the Theory comes into play. Since the cosine of zero degrees is 1, and the cosine of 90 degrees is 0, we use the Cosine codicil of the theory, and assert that the weight on the front wheel is equal to the cosine of the angle in question, times W₁. Simple, right?

Thereby I calculate that if the front wheel were on a bathroom scale 2 inches higher than the rear, and the wheelbase were about 58 inches, as is true for your T3, the angle in question would be sin^-1(2/58) = 2 degrees, and the needed cosine would be cos(2 degrees) = .999. Therefore your T3's front wheel should weigh .999 times what it did when you had the bike level.

You may need a somewhat more accurate scale to check my theoretical prediction with only a 2 inch difference in wheel elevations. Nonetheless I take pride in having offered a specific value rather than a loose generalization.

You could test my theory more accurately by seeing what the front weighs when it is elevated 2 feet. The theory says the weight should be cos[sin^-1(24/58)] = .91 times what it weighed when measured on the level. That would amount to about a (1 - .91)*(475/2) = 21 pound difference.

The Sine/Cosine Theory is the certainly the most sublime and universally applicable of all physical theories, though it is only hit or miss when it comes to accuracy.  I eagerly await your empirical results.

If the measurement at a 2 foot elevation agrees with my theory, it would seem that no one needs to worry about a 2 inch elevation difference. This in turn would mean that none of us need to run out and buy a second scale to weigh our bikes. Scientific theorization coupled with empirical research will once again have worked in tandem to the benefit of all mankind!

Moto

P.S. To weigh the front wheel at a two-foot elevation, place the wheel on a bathroom scale sitting on an automotive hydraulic jack. Then raise the jack until the top surface of the scale is 24 inches above level, and note the weight it registers. Make sure to have someone hold the bike so it doesn't fall over.

M.

[fotoguzzi]

Hats off to you, jbell! Actual instrumentation acquired!

Now you can test theories of the importance of having both wheels on the same level, even without buying another scale to replace the broken one. I hesitated to weigh in (ha ha) when the discussions were just theoretical, but now I'll present my own theory, the Sine/Cosine Theory.

The Sine/Cosine Theory holds that physical problems of this sort can be solved by appeal to either the sine or cosine function, without any messing around with vectors or other actual mathematical analysis. The Theory says that as some relevant angle varies, the required measurement (a force, perhaps) is related either to its sine or cosine, whichever seems more appropriate.

Here is my analysis of bike weighing using the Theory. If the bike is weighed with two scales while it is on the level, the front scale (e.g.) will show weight W₁, which is usually about 50% of the total bike weight. That's the first proposition. The second proposition is that if the bike were rotated upward 90 degrees and stood on its rear wheel pointing straight up in the air, the weight on the front wheel's scale (if it could be positioned under the wheel) would be zero.

Now the Theory comes into play. Since the cosine of zero degrees is 1, and the cosine of 90 degrees is 0, we use the Cosine codicil of the theory, and assert that the weight on the front wheel is equal to the cosine of the angle in question, times W₁. Simple, right?

Thereby I calculate that if the front wheel were on a bathroom scale 2 inches higher than the rear, and the wheelbase were about 58 inches, as is true for your T3, the angle in question would be sin^-1(2/58) = 2 degrees, and the needed cosine would be cos(2 degrees) = .999. Therefore your T3's front wheel should weigh .999 times what it did when you had the bike level.

You may need a somewhat more accurate scale to check my theoretical prediction with only a 2 inch difference in wheel elevations. Nonetheless I take pride in having offered a specific value rather than a loose generalization.

You could test my theory more accurately by seeing what the front weighs when it is elevated 2 feet. The theory says the weight should be cos[sin^-1(24/58)] = .91 times what it weighed when measured on the level. That would amount to about a (1 - .91)*(475/2) = 21 pound difference.

The Sine/Cosine Theory is the certainly the most sublime and universally applicable of all physical theories, though it is only hit or miss when it comes to accuracy.  I eagerly await your empirical results.

If the measurement at a 2 foot elevation agrees with my theory, it would seem that no one needs to worry about a 2 inch elevation difference. This in turn would mean that none of us need to run out and buy a second scale to weigh our bikes. Scientific theorization coupled with empirical research will once again have worked in tandem to the benefit of all mankind!

Moto

P.S. To weigh the front wheel at a two-foot elevation, place the wheel on a bathroom scale sitting on an automotive hydraulic jack. Then raise the jack until the top surface of the scale is 24 inches above level, and note the weight it registers. Make sure to have someone hold the bike so it doesn't fall over.

M.

EXCELLENT! could you make a youtube video of that?
especially, The second proposition is that if the bike were rotated upward 90 degrees and stood on its rear wheel pointing straight up in the air

[jbell]

Moto, about the only thing I remember  of algebraic functions is the old nerd cheer:

Secant, tangent, cosine, sine, 3.14159 gooooooo Spartans.   and yes, it has served me well over the years

[Rough Edge racing]

Bought two $10/330# scales at WalMart.  Set them at wheelbase with 2x4's in between to fill the gap and a little ramp up to the first one.  First up, my 860GT came in at 470#.  Next, the K75RT came in at 540#, both according to spec.  When backing the K75 back down, a loud crack from the first scale and it is buggered up.  Tried to reset and compensate for the difference in a known weight (me).  850 T3 came in at 475# plus throw in another 20# for mufflers for 495#.  Not sure about this one, will get another scale and try again.  Very surprised they came in what the manuals said, expected them to weigh heavier.  First  I tried with a plank across both the scales but that produced varying results and went to tires directly on the scales.

  Action not talk gets results    Some of you need to get out in the real world more often........

[Moto]

EXCELLENT! could you make a youtube video of that?
especially, The second proposition is that if the bike were rotated upward 90 degrees and stood on its rear wheel pointing straight up in the air

The (complete) second proposition is wrong, as I realized in an actual experiment.

M.

[Tom]

Y'ep......take something simple and make it complicated because we can.   

[fotoguzzi]

The (complete) second proposition is wrong, as I realized in an actual experiment.

M.

you recorded it right? put on youtube OIDH. 

[sib]

you recorded it right? put on youtube OIDH. 

(click on the image to see all 3 panes)

[Moto]

(click on the image to see all 3 panes)

Great Dilbert, thanks.

I made paper records of my measurements in two experiments, last night and this morning. But I can't get photobucket's link copying command to work, so won't be sharing them right away.

I redid my experiment this morning to get more accurate results.

I'm going down the rabbit hole again on this one. I think maybe I'll put this aside unless anyone but me is really interested.

In short, the cosine of the angle I indicated before won't do it. A different angle calculated from the actual balancing point of the bike as its front wheel is raised is needed instead. The bike doesn't balance when the front has been raised 90 degrees because its center of mass is above the line drawn between the two axles. This is high school stuff, really, a little bit fun to play with but no great contribution to knowledge!

For a good, unassuming empirical investigation of how to weigh your bike with a bathroom scale, see this youtube video by a central-casting Aussie with his sheila lending a hand:

https://www.youtube.com/watch?v=_z7SUUYGRqU

He demonstrates empirically that weighing each wheel separately on a bathroom scale without worrying about bringing the other wheel up to the same level works well enough. A pleasant viewing experience.

Moto

P.S. Now photobucket's working for me. Here are my two "lab" notes, and photos of my two experimental subjects. I'll leave it at that, for now.









M.

[Tom]

Someone post a pix of the  Mr. Nevada tee.   

[Moto]

Someone post a pix of the  Mr. Nevada tee.   

? Care to be more direct, Tom?

[Tom]

If memory serves me right.  Chuckie post the pix of the tee.