Birth of a kit

[Nudger]

I guess a properly loaded image would help!

[Warkton Tornado No.1]

Post by Nudger » Thu Nov 03, 2016 1:07 pm

I'm reading this thread with interest as it's particularly poignant for me.
I was rushing back from the 2015 Euro Lambretta after receiving the news that my Dad had been killed in an accident.
I was on the German autobahn when my rear brake felt like it was beginning to bind a little. Just at that moment I was able to come off at a service station.
This is what had happened & I think God had decided that for my family, two accidents was enough.

Hey Nudger.

Sorry about your Dad, but pleased that you didn't emulate his tragedy.

My condolences go to you & yours.

As for the broken layshaft, do you still have it?

If you do, there is every chance that an analysis could be carried out.

This could be instrumental in qualifying the problem that exists....

[Nudger]

Thanks for the kind comments WT1.
Yes I do have it actually & never thought of having the damn thing analysed. I just put it down to age related stress.
I'll look into this as I think it would be interesting for all to have a proper report done.

Give me a few weeks as I'm away due to work.

[dscscotty]

Didn't you have one go en-route to Cleethorpes about 3 years ago? When you were bringing me that end can?

That was a rear hub cracking, same scenario though! Tarmac surfing!

I've still got my snapped shaft on my trophy cabinet!, my pal was gonna get it x rayed, just never got round to it

[Warkton Tornado No.1]

Post by Nudger » Thu Nov 03, 2016 1:26 pm

Thanks for the kind comments WT1.
Yes I do have it actually & never thought of having the damn thing analysed. I just put it down to age related stress.
I'll look into this as I think it would be interesting for all to have a proper report done.

Give me a few weeks as I'm away due to work.

Thank you for responding so promptly @ such a busy time for you.

As there appears to be so many instances of broken layshafts about, it’s probably fair to presume that there are others that can be analysed.

I can’t help wondering with the Forum readers being such a resourceful bunch as to whether ‘we’ have any members that might be prepared to be involved in taking this issue onward, even if it takes the form of some well considered advice.

If any analysis is to be performed, I would strongly suggest it needs to be the ‘correct’ analysis, that can give us the kind of information that we need.

Otherwise, the sheer speculation that has been prevalent will have been for no purpose & tantamount to scaremongering with very little factual, scientific basis.

[Warkton Tornado No.1]

Post by dscscotty » Thu Nov 03, 2016 1:40 pm

I've still got my snapped shaft on my trophy cabinet!, my pal was gonna get it x rayed, just never got round to it

Ooops! I’m not ignoring your contribution, but my comments (above) apply to the broken layshaft that you have, too

[Nudger]

Fair point WT1 - I'll see what can be done locally first.

[NorthernJordan]

Didn't you have one go en-route to Cleethorpes about 3 years ago? When you were bringing me that end can?

That was a rear hub cracking, same scenario though! Tarmac surfing!

I've still got my snapped shaft on my trophy cabinet!, my pal was gonna get it x rayed, just never got round to it

I've had that happen too, 2nd or 3rd rally on a Lambretta, I had been doing 70mph on the motorway... Thankfully, I'd slowed for a roundabout, and noticed a wiggling feeling.

Always made me particularly paranoid about this area of a Lambretta. I've had three more go since then for slightly varying reasons... Scary stuff!

[Adam_Winstone]

"Otherwise, the shear speculation...", no pun intended.

Nudger,

Nothing like your level of loss, which I was sorry to read about, but mine went on the way to Euro Austria and it made me decide to rebuild with the spares that I'd taken (the only time I have ever taken a layshaft as a spare!) and to turn back for home. The first thing I did once home was to go onto Facebook to let a few people know that I was home safely, only to read that a contact (mutual friends) had been killed on his Vespa on the way to the Little Brittany rally (Vespa, nothing to do with layshafts). Obviously, I was very sorry to learn of the loss of this pal of pals but it did bring home the risks that we face...

... and make me want to ensure that we do all we can to be as safe as possible.

Adam

[Strummer10]

Hi Guys, interesting reading the posts above and I also personally know of at least two incidences of layshafts shearing down here in Essex. I have contacted the persons concerned to see if they also have retained their layshafts for inspection.

Nudger, also sorry to hear of your circumstances from the post above, that must have been awlful when you needed to get back .

[Dazts1]

Still have mine also. It's also an old Italian one. Available if it's required

[Ken Tucky]

All I can say as a person who has smashed plenty enough transmission components over the years I have been sprinting, is that I have always been concerned about layshaft failure, so any improved version has got to be good thing.
Of course we'll have to presume that the hub mounting boss and hub body will be up to it as well.
I'm still using Series 1 or Spanish hubs..................gulp...........
There's a fair few scooters producing big hp now on the track and the road so hopefully a revised layshaft can only be welcomed.
Richard

[Nudger]

Thanks Strummer10 - yes it was quite emotional to say the least...

[Digger]

I'm still using Series 1 or Spanish hubs..................gulp...........
Richard

Spanish hubs - supposed to be the best you can get?

[Scooterlam]

Just a question.
Do vespa suffer the same issues.
Bmw r1100 weigh 2 1/2 times the weight of a bretta, carry loads more luggage and put 100 bhp thru a stub axle only slightly bigger and are not known for faliures.
Getting rid of the crappy cone method can only be a good thing.

[Ken Tucky]

Hi Digger, just for clarity, yes Spanish hubs are very good, probably the best, but like me, they are all 'old' and may suffer from 'collapse' lol
Richard

[Warkton Tornado No.1]

We surely all must suspect that it is an unfortunate fact that the majority of our beloved Lambrettas only begin to experience any amount of TLC once they become owned by enthusiasts such as us.

Prior to that, many would have been ran with the barest of maintenance, often with a “no expense given” attitude, whether it be a workhorse lifestyle in its native Italy, India or Spain or simply some spotty yoof nearer to home, with no money for a rear hub retaining kit, yet, unable to function without lavishing their paper-round money on chrome or additional tat that serves little function.

Personally, I’ve witnessed this attitude in the UK many times since 1973 & doubt that I’m unique in that sense.

By now, it should be obvious that my strongly held conviction remains that the layshaft will cope with all that it should in terms of the original design remit.

Equally, I am also of the opinion that other factors are most likely to cause the failure, or @ least contribute to it occurring.

Interestingly, the main area where layshafts prove their capability beyond any original intent is within the race & sprint area. Ken Tucky verifies, in so many words, that he has not had a layshaft fail.
That’s not likely to be due to any lack of power or torque or even how gently that may be applied.

I may be going out on a limb here, but I’d venture to say that both sprinters & racers are likely to be a lot more methodical in their approach to the building & maintenance of their machines, although I’ve known @ least one ham-fisted competitor in my time that has even quit to go on to do rather nicely, ahem, in the scooter tuning business.....

So, @ the risk of repeating myself, I don’t believe OEM layshafts will fail simply as the result of being used & fitted properly, even when the torque applied to them via enhanced engines is several times their design intent.



As for:

All I can say as a person who has smashed plenty enough transmission components over the years I have been sprinting, is that I have always been concerned about layshaft failure, so any improved version has got to be good thing.
Of course we'll have to presume that the hub mounting boss and hub body will be up to it as well.
I'm still using Series 1 or Spanish hubs..................gulp...........
There's a fair few scooters producing big hp now on the track and the road so hopefully a revised layshaft can only be welcomed.
Richard

Now, an area where I have known failures to occur is with rear hubs. Within the same parameters as above, OEM Innocenti SIII type are likely to fail certainly within racing. They may be suitable for straight line sprinting as they are subject to different loading.

However, I’ve never known a Serveta hub fail in any circumstance & they are stronger than OEM Innocenti SIII type simply because of their thicker section.

Call me cynical, but just because EmmBee Redevelopments, Pasta Lambretta or whoever, markets a new component claiming it to be 'improved' doesn't mean that is the case.

I've suggested several times now that it shouldn't be difficult for such manufacturers to prove the superiority of their product by a means of certification, from material through to final machining, with all processes in between, including heat treatment & inspection. That process is precisely what Innocenti, Serveta & even SIL would have had to go through before they brought their product to market.

Why are (were) such safeguards in place you may well wonder, but sooner some form of quality control than "Wow! That looks good!"

[Strummer10]

Here's one of the sheared layshafts mentioned in my earlier post, i'm told it went at 65 mph on the A1. This particular layshaft has unfortunately not been retained but i'm chasing the other chap to see if he has the other one. I understand this one sheared a bit back from where the nut sits against the hub.

The original manufactured layshafts were dealing with circa 10 BHP, if the BHP now generally sits anywhere between 16 and 22 BHP on most of the 'Off the shelf' road kits we are now seeing then that's a significant uplift so it would be good to see a nice article looking at the issue to determine cause and what's now seen as best practice to address the issues, backed up with the factual science.


https://www.flickr.com/photos/145916185 ... ed-public/

[Warkton Tornado No.1]

I’m not getting through to some people, I know. Believe me, I don’t stand to gain, but I’d like to say that I’ve tried to communicate my concerns about the problem of broken lay-shafts & how it should be addressed.

So, I’ll take the hit & try another approach, @ the risk of patronising some...

In layman’s terms, the kind of maximum torque likely that the lay-shaft may be subject to is something in the order of 35 lb/ft maximum in drive. Stamping on the rear brake may result in more torque, for all I know!

However, getting back to the drive of 35 lb/ft, we must all have an idea of what that torque must ‘feel’ like from our torque wrenches, I’m sure.

My Milwaukee 18 v impact driver delivers 450 lb/ft through its ½” square drive whilst impacting. That tool can sit for minutes @ a time hammering away @ seized fasteners that resist any attempt @ removal.

So, compare a very optimistic 35 lb/ft being transmitted through Ø 13.7 mm (a guesstimate of the lay-shaft undercut diameter) with 450 lb/ft through 12.7 mm square.

35lb/ft (47.5 Nm) through 147.4 sq mm compared to 450 lb/ft (610 Nm) through 161.3 sq mm means nearly 13 times the torque through an area less than 10% greater.

If you can equate to that, you might be able to agree that lay-shafts are very unlikely to fail based upon purely the design & that other factors are to blame...

[Scooterslag]

Just a question.
Do vespa suffer the same issues.
Bmw r1100 weigh 2 1/2 times the weight of a bretta, carry loads more luggage and put 100 bhp thru a stub axle only slightly bigger and are not known for faliures.
Getting rid of the crappy cone method can only be a good thing.

Never heard of layshaft failure on a Vespa , the nearest I've heard to something similar is the splines shearing in the hub which resulted in a lack of drive but nothing a catastrophic as a lambretta layshaft/hub failure. I've only had two incidents of back wheel failure on a vespa- both when I was young and maintenance was a dirty word - first was when my hub studs wore through and the second when I just popped on the hubnut and didn't tightened it enough or fit the castle nut or split pin , result - my back wheel falling off going around a corner Always hated the design of the lambretta layshaft/hub arrangement, the fact that the design has it tightened up to 120 foot pounds before its even been turned by the engine or hit any road imperfections can't help with things , the Vespa design doesn't put such strain on any similar components and so its far more safer and reliable. Paul