Lawnmower blade inflation ?

Yes, but the blade won't revolve on the nail unless badly out of balance and so may only move a small way before the nail rolls up the inside of the hole and stops it going any further. Plus you aren't supporting the blade along it's centre line but above it (depending on the ratio of the diameter of the nail and the hole etc) and therefore also have more of the mass of the blade *below* the centreline as well (further reducing the sensitivity).

Ok, it would give you a reasonable idea of which side is heaver when initially set horizontally but I'd much prefer that the blade was able to fully rotate freely and about it's centre and then I could be sure there is no heavy spot once it stops spinning.

The motorcycle / scooter wheel balancing spindle made works that way.

I turned two ally cones that sit and are locked on a silver steel shaft and on both ends of the shaft are fitted light / un-sealed bearings.

You remove one bearing and cone, pass though the wheel and bearings, replace the cone and bearing and centre the wheel and tension the cones onto the spindle and against the wheel (bearings).

You then support the two bearings on axle stands or similar and then note where the wheel stops. Temporarily attach some weights to the rim at the top, turn the wheel though 90 Deg and let go, you will quickly see if you have added the right weight by which way it turns.

Rinse-repeat till after gently spinning the wheel it stops at any random position. Properly fix the balance weights, re-check and use. ;-)

Cheers, T i m

... and so may only move a small way before the nail rolls up the

Start with the blade horizontal on the nail and then see what it does. At that time the contact point between the nail IS directly above the centre of the blade hole. Which way it then turns indicates which half of the blade is heavier. That's all you need to know in order to get filing - and is all that this indicative observation can tell you.

PA

I have done with all sorts of things. ;-)

Agreed.

Agreed, assuming there is any reasonable difference. And you are right to say 'which way it then turns' is correct as the indication may only be very small, because of the (poor) design of the pivot and the fact that the pivot will be above the COG and not on it.

The bigger the mounting hole in the blade the worse all those effects will be. It would be like balancing a painting by hanging it from one nail in the middle near the top. ;-)

Quite, so 'limited'.

Once the difference in the weight between the two sides is low, it would be like trying to use a see-saw to measure the difference in weight between two pillows. ;-)

Will balancing a mower blade on a nail give you a rough idea of it's balance? Yes.

Will balancing a mower blade on a nail give you a useable balancing solution? Possibly.

Will balancing a mower blade on a nail give you the best / most accurate level of (static) balance? No, much better to run it on a shaft on bearings or parallel bars.

Cheers, T i m

Horses for courses, then.

PA

Well, sort of but if you *are* looking for the blade to be 'balanced' then you need to use a system that allows you to get as close as possible to that as it's either (static) balanced or it's not.

So I guess the nearest the 'horses for courses' would apply is how much 'off balance' are you willing to accept. ;-)

You can imagine the process being laid out like a balance scale where the pivot for the arm is at least in line with the support points for the dish hooks, if not below it.

If the pivot is below the hook points it will make the scale more sensitive as when the arm is off horizontal the out_of_balance mass of the arm (the different amount of material above the pivot compared with below it) will exaggerate any movement.

If the pivot point is above the level of the hook points the balance will be less sensitive (and worse the further off horizontal you go) as it will try to 'self centre'. This is the scenario of the mover blade on the nail as the bolt hole is likely to be a much larger diameter than the nail so the blade with hang 'low' on the pivot (for starters).

The 'nail as a pivot' could be improved itself by filing the shaft of the nail into an arrowhead section, allowing the mower blade to 'rock' (not roll <g>) on the nail / pivot.

Cheers, T i m

My point is one of inconsistency. If you want the degree of "balance" that you seem to seeking, can you then refit the blade in the *exactly* right position. How do you allow for any play in the retaining fitment on the mower?

A chain is only as strong as its weakest link.

PA

Have a look at high-end Hondas. Loads of fixing play. Some Mountfords, too.

You're making my point ! The sort of precision balancing you talk of is way OTT when it comes to mover blades.

QED

PA

I?ve never come across a mower blade fixing that didn?t centralise the blade on the shaft.

Talking of imbalance, when was the last time anyone *ever* replaced a crank seal or bearing damaged by an out of balance blade?

Tim

In reality lawnmower blades have limited freedom of movement before bolting up. WExepreimec wiytj model aircraft proips shows that balancing to as far as you can detect is way better than how the prop may arrive as new, and more than good enough to reduce vibration to a minimum.

My lawnmower blades are shaking the s*it of of the cutter deck - they are probably several ounces off balance. When I have finished mulching all the twigs that have fallen over winter, i'll balance another set and change them

I think I have

I bow to your experience. Sounds like poor design not to incorporate some sort of simple blade centralisation though.

Not me, I think you mean T i m.

Agreed.

Tim+

How odd?

But then again, maybe not? ;-)

Tim

T had ro do a lot of repairs on te mower when I got it back from te ex - she had destroyed it - but had had the bearings in the deck replaced I think. I had to get a new deck but retrofitted the old bearings

My lawnmower is alsoa heavy duty chipper and mulcher. Anything wooden under an inch diameter gets left in the grass

Naturally blade wear is very high