The end of the Lambretta crank as we know it ???

[drunkmunkey6969]

Mark sent some helpful info on various cranks:

Facts: If a crank I built goes together at 10 tons on my press it is tight, race tight, no need to weld it, as welding ALWAYS pulls the crank out of alignment! And only some welding works, TIGing will crack.

Alignment: This is very important, Lambretta cranks are a crap design, you are lucky if you can get a genuine crank to line up correctly. So, MEC cranks don't tighten at 10 tons, more like 5 which is ok, some, certain well known supposedly race ones go together at 3 tons! Anything below 4 tons will spin! Cranks will spin if assembled with oil or grease.

Surface: The fact is the crank width of a Lambretta is too thin and not enough surface area to lock onto the pin, hence we all use oversized pins! But this then also causes a problem! The tighter the pin gets the more chance of cracking a web, even if its doesn't crack the pin will deform the area around the pin, making it go egg shaped and loosing more grip.

Pins: With some cranks, you can put massively over sized pins, that take 10 tons, but will still be loose! Material and heat treating is a major factor here! The MBD Race-Tour crank is designed to work and that means our full circle cranks have more area around the pin, which doesn't distort as much and stays tight.

Development: We have continually developed our cranks from the first batch and they are now where Im prepared to say 'Probably the best Lambretta crank ever made'. They are hand made, and we are all human, if we do get a faulty crank, there are tricks I know to repair them, so all is not lost! These problems are getting less and less and its only the first batch that I have to rework and usually after many miles on them anyway.

Shims: You HAVE to use crank shims, anyone using cranks with no shims will over heat the rod and bearing and it will fail. 0.5mm crankshims also fail, 1mm are best! Using 130 roller racing Indian bearings will also fail.

Lastly: Innocenti, Mazzucelli and SIL cranks have a forging floor in them and will eventually crack, not outwards to the extremities but across the weaker area to the bob weight. Others will not stay tight what ever you do. For this reason I got fed up with making one off crankshafts and made the Race-Tour ones

Cranks lesson here enduth. Lot more to say, but Im sure it will get boring to you and all in the end!

[tony]

Quote from Mark
"Pins: With some cranks, you can put massively over sized pins, that take 10 tons, but will still be loose! Material and heat treating is a major factor here! The MBD Race-Tour crank is designed to work and that means our full circle cranks have more area around the pin, which doesn't distort as much and stays tight.
"

Which is what I was saying about the possibilty of the bell cranks failing in our application-not enough meat.

I think the falc crank doesnt use shims tho.. i think he done it to get the most surface area he could to provide a stable solid crank..Its worth a look considering it has been designed by a International Gp tuner whose kit produces almost 5 times the original output of the engine it was designed for. No other kit producer for geared scooters has that in their porfolio.
http://www.sip-scootershop.com/Products ... +FALC.aspx

Also..I think Charlie wanted to see grp4 and lambretta tuning progress when he talked about the lpc ideas. I told him off for talking about it tbh. I felt he gave too much away. He doesnt do anything without scientific study followed by thorough testing. And he tested the primary comp ideas thoroughly on many machines and of course his race motors. It isnt a red herring as someone said. If any of you havent had the results you were maybe expecting then maybe its because his motors are designed to work as one. If he mods a barrel, he will make a new pipe to work with the mods and head too of required. There is no 'i'll scoop a bit more out of here and see' with him. Every component has to work in sync with the other. So bringing us back for instance..if you have a pipe that isnt working as well as it could, or wasnt designed properly for that motor with those angles and areas then a hpc bottom end will help as the other components arent doing their job properly. However if everything is working together and designed around the Low pc idea then the result is more power. Why.. well I'm sure you know or someone will know the answer

[J1MS]

Anyone.. ...

[drunkmunkey6969]

I would guess he means that its a combination of increased flow volume, plus decreased crank case pressure , meaning less resistance on the power stroke, leading to increased revs, and the parts all working in harmony to make sure the new increased volume and flow is in the right place at the right time. eg - the pipe not stuffing mix back into the transfers, or the flow not shooting the charge out of the exhaust etc....thus keeping max volume of charge and flow in the right place at the right time, with least resistance to sap the power and help increase revs.

Just my guess like.

Or is Tony just playing with us and scoffing with Charlie whilst we fumble atround in the dark?

I don't know about red-herrings, i feel more like barking seal being thrown fish.......arf arf!

But fear not drunk 'Cleuso' munkey is on the job!

[paulmgreen]

I
Or is Tony just playing with us and scoffing with Charlie whilst we fumble atround in the dark?

I don't know about red-herrings, i feel more like barking seal being thrown fish.......arf arf!

But fear not drunk 'Cleuso' munkey is on the job!

Reckon Tony and The Charlester have more pressing things to think about lol :ninja:

[drunkmunkey6969]

Reckon Tony and Ther Charlester have more pressing things to think about lol :ninja:

Nonsense...what could be more important than this forum?

I'm sure Charlie has this forum projected onto a big screen in his workshop, and receives thread updates to his Blackberry so that he can pick up tuning tips.

[Avantone]

So going back to the bell shaped webs rather than the LPC debate:

1. Would the shape of the webs cause turbulence?

2. Is that a good thing or a bad thing?

3. Could the shape of the trailing edge be used to help fill the crankcase?

4. Would it be beneficial to have a better shaped leading edge to reduce drag?

5. When you remove the material from the webs, how do you address the motors balance ....... scientific or guess?

6. Is there a better way of reducing PC i.e. skimming the webs, removing crankcase material from around the webs, adding an additional reservoir to the crankcase, longer conrod, other?

[DJ 240]

Hello..

And where do we start?

IF........Your chosen holy grail, to the exclusion of everything else, is that "LOWER PRIMARY COMPRESSION IS BETTER", then what's the problem? With a large drill, simply make holes it the crankcasing. This will reduce the PR to ZERO, therfore the engine must run the best? Of course not, to carry out this modification would be totally senseless.

A Two Stroke engine is a simple design that is immensly complicated in it's operation. Every aspect of design, when given to comittee decision, is open to debate. For example, we must RAISE the exhaust port to produce more power? YES! This allows the port to open earlier hence increasing revs. Yet to RAISE the exhaust port will reduce the power stroke, and therefore reduce power. Who is right then? The very simple answer is.... NO-ONE! Every engine configuration, and every tuners ideas of the modifications required to make that engine breathe better and produce more power will be different. Who was it that said if you have a million monkeys and a million typwriters, eventually you will get Shakespear?

I find it amazing that with so many people messing around with so many engines, that why is it that there are no "Giant Leaps"? Why is the performance of so many people ideas so very similar?

Well, one reason is that to have such a strange fixation on what is one tiny aspect of the total two stroke package cannot produce the radical results that some readers seem to expect. If it was, one of those million monkeys would have found it by now!

I can't learn to be a Rembrandt (is that how it's spllelled??) overnight. I believe I have a flair and what is far more necessary, a basic technical undertanding of "how things work". It is plain that reading these threads, that many of the writers don't have that knowledge. Does that make me better? Others may have talents far in excess of mine regarding other far more important and valuable things in life.

Maybe if I'd been a nuclear scientist I would have been richer. At least a life of thirty-odd years playing with Lambrettas taught me that nothing is too simple when it comes to making massive changes in specific power output. Trouble is..... it didn't make me rich. But I enjoyed it along the way, and I still enjoy the debate raised!

Chow!

Dj

[Avantone]

LOL, I knew someone would be drawn out sooner or later - thanks very much for taking the time to reply and contribute Dave.

As you'll probably realise most of us have a keen interest and inquisitive minds and like debating this sort of stuff - no harm and it keeps us off the streets

The people that have invested lots of time and money developing this stuff (and have a commercial interest) aren't likely to blab it out on a public forum - we understand that, but a few tit-bits are appreciated.

[sean brady scooters]

thanks dave.......for taking the time to contribute your comments on here.............
they are of course much appreciated...............