Britbike forum Forums Projects started by Britbike forum members Members bike projects 0.001" or Worse Accuracy in the Garage

May be of interest in the context of the current discussion:

https://www.britbike.com/forums/ubb...hrottle-slide-synchronisation#Post846732

Weight

The electronic scale in the next photograph is at one limit of motorcycle-appropriate weight-measuring capabilities, with its 10 g maximum and 2 mg resolution.



Such a scale is useful for small items, like AMAL jets. The next-larger scale is 200 g ±10 mg, which allowed me to determine that the spring constant of the aftermarket brushes in a Bosch ZEV magneto was 25% too high compared with the springs on Lucas brushes.



Along with a third similar-looking scale, these cover weights from less than 1 g (±5 mg) up to 6 kg (±0.5 g) to deal with many motorcycle parts, such as comparing the weights of two pistons, or measuring the weight of the small end of a connecting rod.



At the other end of appropriate weight-measuring capabilities is the scale in the next photograph, with its 600 lb. maximum and 0.1 lb. resolution.



This scale is useful for measuring the weight of gearboxes, engines, or even complete motorcycles. It's seen in this photograph hanging from the jib crane over my lathe and mill, but it also finds use on the engine hoist.

No weight scale, or other measuring instrument, can be trusted without checking its calibration, and for motorcycle purposes there are weights from 5 g (±20 µg) to 2 kg (±0.3g).



I would need a heavier calibration weight for the 600 lb. scale if I wanted to be sure of its accuracy at, say, 200 lbs., but the scale gives the correct weight with my two 2 kg (~9 lbs. total) weights so I trust that its accuracy at higher weights is good enough for any purpose I've had for it thus far.

what are you doing tbat makes you want to weigh carburetor jets?

He’s running out of things to do.

Although I can't argue that triton thrasher is wrong, about 15 years ago I started a still-running experiment on the effect of ethanol on the metals used in carburetors. I accurately weighed jets and pieces of a sacrificial carburetor and placed them in sealed jars of "pure" gasoline, E10 gasoline, and 100% ethanol. I used to measure them more frequently, but now I only do it every few years. There are plenty of dire warnings in magazines that imply carburetors will dissolve under the onslaught of ethanol (similar to the warnings a few decades ago about the effect of Pb-free gasoline on valve seats). However, as of the last time I weighed the pieces there had been no measurable loss in weight whatever. Anyway, an experiment like this needs a sensitive scale that has been accurately calibrated.

No, our dear MMan is only running out of things to do during non-riding season, in the middle of a once-in-a-lifetime pandemic (we can hope).

As I have done quite effectively in the past, I full intend to waste a lot of MMan's time just as soon as weather and plagues allow.

Now see what you've made me do

How about adding some water contaminated ethanol to your ongoing study?
Makes sense to me because that's what usually happens with ethanol.

I'm way ahead of you. At least in the sense of having thought to do that several years ago, although not in the sense of actually having done it as yet. I'll get around to doing it mañana...

I should add that my experiment was to test the efficacy of fuel stabilizers which, as a result of this and another experiment, I do not waste my money on. If I plan for a bike to be parked for more than a week, I drain the carburetor. The problem I find isn't that the carburetor dissolves because of the fuel, it's that a hard membrane forms in the pilot jet.

thats interesting. long term stuff.

i knew a petrologist who was interested in tbe effects of wind weathering on stone outcrops in antarctica . he cut a bunch of little tiles of various kinds of rocks he was interested in, mounted em on a post and stuck it in the ground out there for the wind and snow and ice to wear away. had a steel plate on tbe post that explained what was going on in about five languages, stamped into the steel.

its one of those hundreds-of-years-long experiments that he will never live to see the results of, but that nobody in the future can analyze unless somebody like him sets it up now and walks away.

Having nothing whatever to do with motorcycles, and for reasons too long to explain, I've been running an experiment since February 28, 2004 to watch the oxidation of an iron mirror I polished at that time. Because the humidity in Arizona is a lot lower than that of Belgium, I have the iron mirror on a ledge in the bathroom where the humidity rises to above 50% for a few hours each day, before dropping back to arid levels. As can be seen, only a small fraction of the surface area still resembles anything like the original shiny metal.

you have to explain why belgium, at least.

OK, the short explanation is that artists like Jan van Eyck and Robert Campin worked in and near Bruges in the early 1400s. A longer explanation for how that is related to my interest in mirrors can be found here..

Any idea where I might find instructions on how to make the mirror? Ones that do not require crushing and squeezing worms through a cloth. A substitute for blood would be appreciated as well…. trying to keep the peace around here.

Sometimes the digressions are more interesting than the core postings!

Way way back , probably on here or even the Pitt Stop . some one posted a differential manometer which was just 4' of clear tube with some water in it and a touch of die
Hooked up the balance tubes of an A 65 makes for very accurate balancing
If the worse happens then the only consequence with be carbon splatter all over the workshop wall & scoured cylinder walls

I've not seen the post with a manometer of 4" using water, but sounds like it could work well.

Below is a pic of my Morgan Carbtune which I bought around 1988, hasn't been used for many years but the mercury is still in it.

I pulled a vacuum on both tubes and the mercury rose up, so it still seems to work.

I believe there are built-in fibre baffles at the top of the tubes to prevent the mercury from being sucked out and also to stabilise the airflow. So I don't think there is much risk of the mercury being sucked out.

The carb tune measures approx 18" overall and has cm gradings from 10 to 35, though what scale the represent is unknown.

Truing and Balancing



After a crankshaft is assembled, a set of bench centers can be used to check that the shafts are Concentric, and that the flywheels don't have any side-to-side wobble.

A set of weights, along with balancing rollers or knife edges, is needed for balancing a crankshaft, as shown in the next photograph.



Weights are added or subtracted until the item being measured is in balance, after which the wire plus string of weights is weighed on the scale. If the piston and small end weights are accurately known, the rollers/knife edge has to have sufficient sensitivity to allow the balance weight to be determined to ~±3 g for the balance factor to be calculated to better than 1%. The 0.09 oz.-in. sensitivity of these balancing rollers corresponds to a weight sensitivity of 0.2 g at the radius of the crankpin (i.e. on the end of the connecting rod) on an Ariel crankshaft.

It can be seen in the photograph that the connecting rod will extend below the base of these rollers as the crankshaft is rotated, so I made the stand it's sitting on to extend the height from the table to the shaft to 14½". This also allows the rollers to be used for balancing complete wheels with tires, although the sensitivity of these rollers is overkill for this purpose since it would allow balancing a complete wheel to within about 0.3 grams, which is ~15–20× better than the smallest weights that are sold.

Although I've never used it to balance wheels, so I don't know its sensitivity, my wheel truing stand uses bearings to support the shaft, and is sold as being good for balancing wheels, so presumably it works well enough for this purpose.



A quick search found that ¼ oz. (7.1 grams) seem to be the smallest wheel weights sold, which implies that truing stands or rollers that have at least that sensitivity would be good enough for balancing motorcycle wheels.

That flywheel reminds me of rebuilding a 900 Sportster engine 30 years ago...Truing the flywheels on the tapered fit connecting rod pin..I didn't have the best stand ...Very difficult to get .001 accuracy...

I managed 0.001" on both side of my Alloy Clipper crankshaft, but at that time I also measured a new Phil Pearson crankshaft and found 0.001" on the drive side and 0.002" on the timing side.

Just wanted to let you know that I really enjoyed that video. Especially the end when you called art historians blind, ignorant and overeducated. Talk about canon fire.
Wish I could have attended your first seminar on the subject. I know I’m a little sick (well maybe a lot), but I do take pleasure in those sorts of things.

I was still trying to be somewhat diplomatic at the time of that lecture. You should hear what I have to say now...

By the way, I didn't listen to it again, but are you sure I called them overeducated, not undereducated? If I called them overeducated, I mispoke. Their education is all about trees, missing out on forests.

Actually you didn’t call them overeducated, it was just implied. You had mentioned that…other than an hour with David Hockney mixing water colours, you were self taught. It gave you fresh eyes and made discoveries because of it. Probably where you went wrong… they all collectively went into vapor lock.
Interesting how some folks get hostile when presented with something that doesn’t dovetail into their beliefs or what they were taught at the brick factory. Yes it has to pass the acid test, but something to be said about having an open mind.

Two incidents immediately come to mind. Well, more than that, but two will do for now.

Early on in our work David was explaining something to me from art history and I apologized that I wasn't aware of whatever it was because I'd never taken an art history class. He said, that was good, because it meant I was free to think independently.

The Director of a very famous art museum had been there the day before one trip I made to his studio. Although the guy was there for a different reason, David said he started to explain what the two of us had been discovering, but the guy cut off the discussion by saying his own interest was in 19th century French art. That was one of many incidents that informed my understanding of art historians.