1000 triple 180 gearshaft/layshaft working principles

[Enrico]

I am curious about the working principles of the gearbox of the triple 180 Laverda 1000.
The pinion that transfers the motion through the transmission chain to the rear wheel is in axis with the main shaft (gear shaft).
How can the layshaft create a mechanical advantage?
1st gear should be the bigger gear on the main shaft engaged with the smaller gear on the layshaft.
My question is: the main shaft is a solid piece or somewhere is disconnected taking the mechanical advantage from the layshaft?
Or better, how the layshaft ensures the mechanical advantage?
Attached a couple of pictures taken from the sample engine exposed at the Laverda museum in Breganze.
Thank you all to help me to solve my curiosity

 

[andre g]

the main shaft is splitted at the fifth gear as long as the first 4 gears are used. For the first 4 gears the mainshaft transfers the load to the layshaft and it will connect to the fith gear sprocket and so to the secondary chain.
In 5th gear the layshaft is running free and the mainshaft is connected to the 5th gear wheel, it is also called the direct 5th gear which is running now with the same speed as the coupling and the main shaft.
This construction is a weak point of the gearbox. Under high power the mainshaft connection at the 5th gear is not stiff enough and the bearing, ( there are two versions, needle bearing or bronce bush) will be overloaded and fail.

Redax developed a conversion of the 5th gear wheel and part of the shaft where he supported it at the outer engine cover over the secondary chain sprocket.

Hope you can understand
Andre

 

[Enrico]

Thank you very much Andre, well explained.
I hope somehow to find a video that shows this in detail.
Your explanation matches, of course, with the drawings in the manual and now is clear for me.

 

[sfcpiet]

Imho, the gearbox in stock form is sturdy enough for the power it was intended for. Once this is excessively exceeded, around 110+ hp, problems can raise their ugly heads... The design of the 180° gearbox is directly based on the 750 'box, which started out having to deal with 50hp! The triple mainshaft was lengthened to accomodate the primary chain run of the longer crankshaft and the selector drum was mirrored to suit the improved selector mechanism in order to retain the shift sequence. Apart from minor reinforcements in the sleeve gear dogs and partially different gear ratios, the 'boxes are literally identical. The 120° engines got a completely revised gearbox that was almost bullet-proof, save for a single flaw.

Incorrect chain tension causes the most harm to the mainshaft, especially those with needle bearings in the sleeve output shaft. 120° owners know this just too well. Too much chain slack is definitely safer than too little, it's always wise to re-check chain tension with the bike on its wheels and the rider seated.

It's amazing how little attention is turned to gearboxes, I've found engines on their 3rd. set of pistons (at least), with the gearbox still running on the original bushes and bearings. Excessive wear in e.g. the 4th. gear mainshaft gear bush (the physically weakest and most damage-prone gear) can cause it to over-ride its companion, with disastrous results. Not to mention the rattle that comes with excessive slop.

piet

 

[Paul Marx]

Imho, the gearbox in stock form is sturdy enough for the power it was intended for. Once this is excessively exceeded, around 110+ hp, problems can raise their ugly heads... The design of the 180° gearbox is directly based on the 750 'box, which started out having to deal with 50hp! The triple mainshaft was lengthened to accomodate the primary chain run of the longer crankshaft and the selector drum was mirrored to suit the improved selector mechanism in order to retain the shift sequence. Apart from minor reinforcements in the sleeve gear dogs and partially different gear ratios, the 'boxes are literally identical. The 120° engines got a completely revised gearbox that was almost bullet-proof, save for a single flaw.

Incorrect chain tension causes the most harm to the mainshaft, especially those with needle bearings in the sleeve output shaft. 120° owners know this just too well. Too much chain slack is definitely safer than too little, it's always wise to re-check chain tension with the bike on its wheels and the rider seated.

It's amazing how little attention is turned to gearboxes, I've found engines on their 3rd. set of pistons (at least), with the gearbox still running on the original bushes and bearings. Excessive wear in e.g. the 4th. gear mainshaft gear bush (the physically weakest and most damage-prone gear) can cause it to over-ride its companion, with disastrous results. Not to mention the rattle that comes with excessive slop.

piet

Piero Laverda once mentioned to me that Moto Laverda had a huge stock of gearbox parts because they never broke.
I had a bronze bush, 3rd gear, disintegrate on the SF2 many years ago. I put that down to the oil seriously overheating during a monster jam in Paris during an Amicale 750 Laverda meeting. Those there will remember it, we were stopping regularly because the fuel was boiling in the float bowls of the triples.
Paul

 

[Enrico]

I’ve found this very interesting video that at 2:34 shows how the gearbox works at each gear, neutral included.
This video is related to a 750 SF, but the gearbox works in the same way, no changes compared to 1000.

I personally do not have any other question on this.
Thanks all for the support.

 

[sfcpiet]

Piero Laverda once mentioned to me that Moto Laverda had a huge stock of gearbox parts because they never broke.
I had a bronze bush, 3rd gear, disintegrate on the SF2 many years ago. I put that down to the oil seriously overheating during a monster jam in Paris during an Amicale 750 Laverda meeting. Those there will remember it, we were stopping regularly because the fuel was boiling in the float bowls of the triples.
Paul

Pretty wild assumption, Paul.

Why should only a single bush be affected? Totally knackered beforehand would be closer to the truth.

That Laverda gearboxes last "forever" is but a myth. The gears suffer from pitting just as any other marque, especially 4th. and 5th. layshaft gears. In stark contrast to most other gearbox bits, new ones are almost unobtanium by now.

piet

 

[Paul Marx]

Pretty wild assumption, Paul.

Why should only a single bush be affected? Totally knackered beforehand would be closer to the truth.

That Laverda gearboxes last "forever" is but a myth. The gears suffer from pitting just as any other marque, especially 4th. and 5th. layshaft gears. In stark contrast to most other gearbox bits, new ones are almost unobtanium by now.

piet

You're no doubt right Piet. The bronze bush disappeared when the bike had no more than 40 000km.
There was some pitting on a couple of gears on my S when I opened the engine back in the 90s.
I let it be.
We'll see.
Paul