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[Betsy1969]

I’ve bought this of fleabay as it looked cheap. Only thing is I don’t know exactly what it is .
Any ideas ?

[nathanglasgow]

1st and 2nd mainshaft gear?

[Betsy1969]

1st and 2nd mainshaft gear?

Well , that’s what it was advertised as so at least it was described correctly. I don’t need one at present but I thought it was worth getting to put into stock .

[diffwhine]

Looks in good shape. I need to check my parts books, but I think it varied in number of teeth depending on the ratio of the gearbox. One tonnes for example had different box ratios.

[Betsy1969]

That’s interesting diffwhine . I thought if it says 37 teeth then there must be at least one more variation

[diffwhine]

Looks like the transfer box was the main difference on 1 tonne models, but the gear we are talking about here, changed depending on box suffix. I've got a suffix D box in pieces, so will investigate tomorrow and count the teeth!

[diffwhine]

I think its a standard 511205 1st gear mainshaft suffix C onwards (until the all synchro box came out).

[Larry S.]

This reminds me of when I rebuilt Grover's transmission.

I needed one of those and sourced the one the parts book said I needed.  It was tge wrong one!!!

In frustration I contacted a gent here in the States that coukd rebuild Series transmissions blindfolded.  Told him what was going on and supplied pics and vids to see if he could help figure out what I was missing and/or doing wrong.  It took 3 months and the help of four Rover guys, on three continents to figure it out.

They guy tried to explain it to me in detail, but I'm no mechanic so he had to explain it to me as though I was 5 years old.  In a nut shell he said the gearbox was geared really low - basically my 'HI' gear was everyone else's 'LO' gear and the work had been done at the factory.  He then offered me almost the amount I paid for Grover just for the gearbox - I declined.

While talking with him the light bulb came on in regard to an incident that happened soon after purchasing Grover.  We had rented a boom lift to do some tree trimming on our property.  When we were finished for tge day we parked the thing up against a slight rise in the yard.  That night a freak thunderstorm hit and the boom lift settled a few inches into mud.  Due to the mud, and the lift's tires right up against that low rise (similar to having a trailers tires wedged up against a curb),  tge thing was stuck.  To make matters worse it would have to be pulled up onto that low rise, it couldn't be pulled backwards.

The father-in-law tried to pull it up and over using his truck - nothing.  We then got my dad's bigger truck - nothing.  Then we tried my brother's truck, even bigger, with 4wheel drive - it budged the thing but wouldn't move enough, and my brother's truck tore up the yard.

I suggested using Grover and they laughed.  Grover was the smallest vehicle there and the locking hubs were not reliable.  But I decided to try it anyway.

Engaged the hubs, put it in low, and slowly moved forward; the boom lift hesitated and then started moving upward and onward!  It was as if driving on a flat surface - no issues at all.  Grover and I had the last laugh.

I related this to the main guy who helped me with the gearbox; he said that that low gearing is what did it.

[Clifford Pope]

Presumably if there are versions of a gear wheel with different numbers of teeth then they have to be matched in pairs? The spacing between adjacent teeth will be slightly different.

I remember from my Meccano days that the standard 1:3 pair of gears came in two versions - old ones that I'd inherited from my father had 19 and 57 teeth, the later ones had 20 and 60 teeth. Although the ratios of the pair were the same, an unmatched pair didn't run quite smoothly, and had a very slightly different ratio.

[agg221]

Presumably if there are versions of a gear wheel with different numbers of teeth then they have to be matched in pairs? The spacing between adjacent teeth will be slightly different.

Ah, modulus and pitch circle diameter! In essence, yes. Someone will wince when they read this, but it is about right.

Imagine you took the outside a gear, cut the bit with the teeth on off, straightened it out and laid it out as a flat strip (like a rack on a rack and pinion). It would be a certain length, have a certain number of teeth and the teeth would have a certain shape. If you want to make another gear that runs properly with it, making up another strip with the same shape teeth and wrapping it round a circle would work fine, so long as the length is a whole number of teeth. That means you can make any number of teeth mesh with any other number of teeth (unless the number gets too small and doesn't wrap nicely around the circle).

However, from the length of the strip, which is the circumference of a circle, divided by Pi (approximately 3.14) you can get the diameter of the circle it will wrap around. If you have two gears running together, you can then use the radius of each gear (minus the amount they mesh by, which is dependent on the shape) to work out how far apart the centres of the shafts they run on should be. If you change one gear for another with the same tooth shape it will will run perfectly if you adjust the spacing. However in a gearbox where the spacing is fixed, you have to select ratios which will run properly as pairs of the right diameter, and/or change the tooth shape to make them fit.

As an aside, this is why the arrangement for the gear-cutting train on a lathe allows the gear train to be slid up and down to change the centre distance.

So, if your meccano gears had the same shape teeth, you would have been able to set them up any way you liked if you had a way to adjust the centre distance but otherwise you would have to pair them correctly to get them to mesh properly. If they had different shaped teeth there would be no way to pair them.

Alec

[Leon]

I think its a standard 511205 1st gear mainshaft suffix C onwards (until the all synchro box came out).

511205 is a 30 tooth