Modern Vespa

Don't call me Shirley...

^^

we sent our best guy out to check it, Justin Case

He said that Seamus Finé had already looked at it and the foreman Alex Eptable signed off on the job.

That's some A+ work right there--by which I mean the choice of gif, of course .

That retaining ring looks downright Steampunk. It's almost a shame that it's going to be buttoned up inside the cases, hopefully not to be seen by mortal eyes for some time to come.

I think you have more than enough holding force there. Honestly, I'd think a few 1mm steel tabs like on the seal holder for the Sprint would probably have been adequate and could have fit into the clearance between the crank and the bearing, but this is one of those cases where if it's worth killing, it's worth overkilling.

^^^ A chandlerism for the books ^^^

Oh - wait until you see my gas tank concept for my other one... 🙂 My thinking on it was actually driven by a comment you previously made about the helical gears creating a big axial force.
That hadn't previously dawned on me.
I was trying to imagine a solution that would work both statically and dynamically as that force increases through the power band.

Jack - I considered using 2 or 4 ears - but realized that without CNC - a circular retaining ring would be much easier to execute.

So-Cal Im pretty sure I have one of them in my signature!

General:
My motor calls for the crank to stay stable to the .05mm.
If the crank shifts .05, I would remain at .10 clearance or less between side of crank and pad.
That keeps me nice and tight and efficient at sucking fuel in.
There will be some flex to the case or the retaining ring that will occur as I load the motor.
I may opt for a .03-.04 static gap - knowing it will open then re-close - as it experiences load from torque and clutch.

With this ring - it will then come down to the fit of the crank to the bearing ID - and if I am able to lock that using a loctite compound (please don't make me have to go to a circlip...)

Im also going to make my inlet .5 wider again this time.
With the .05 true clearance on its entire boarder - I think I will have plenty of sealing until the pad is worn out with grit.
The pad is now basically replaceable.
Anytime I exchanged main bearings - I can torch out the pad and put a new in.

My thinking on the overlap.
1. the 1.2 or 1.5MM overlap is an opinion from experience - but there is no hard science on it that I am aware of.
2. normally - because your crank DOES shift - going less means that a .5mm shift already brings you down to about .75 overlap on one side (and a 2.25mm on the other). But as I load the crank axially - my overlap will only increase - and I have locked it against any significant movement in any event.

Need to think about a mod that would let me replace the pad from the top - allowing me to choose what intake timing I want to run.
Then we could have 2 or 3 more pages on those calcs ea. time.
🙂

The current situation:

That's a pretty good hint that you dropped there

Oh boy, spinning machinery and liquid courage never good. Time to walk away and call it a day.

Is this a before and after photo set?

Would beg the question; is that a shot of celebration or a shot of consolation?

That, my friends, was a shot of inspiration - in the form of Patron.
Since you asked about timing:
It occurred just after a pinch of salt, and just prior to a bite of lime.
All those things occurred after the garage lights had been dimmed.

Speaking of dim - I might be slow - but I don't drink and machine.
Like fruit and vegetables.
They don't mix (but thanks for looking out for me!)

The spinny things were a foreshadow.
You remember foreshadow? That was the concept the English teacher was pitching while mentally undressing the girls (or boys) that he fancied.
Anyhoo - that little spinny bit I showed was an adapter.

I've shifted gears (lord - the puns just write themselves).
I plan to build this thing and make it last.
Out over my skis.
Glass jaw presented.
Last version when 6.2 miles.

Cases are cracked on the fly side.
Not helpful.
Picture below shows the spot.
Was it the heat?
The pounding?
Some combination no doubt.

Since we're this deep - let's talk bearings.
Fly side old Vespas use 62mm ball bearing.
They lock the fly side from moving axially.
Very solid - but any push on crank from clutch side = deformation of the crank webs at the pin - 'cause it is pushing into that bearing.
That's how my motor failed (prior to this L shaped craziness).

P motors use needle bearings to alleviate any axial resistance on the fly side - good but perhaps not so robust?
Y'all all liked the T5 bearing - so I based my solution of that.
T5 uses the P needle bearings on steroids - fat and fewer needles.
Both of these eradicate resistance to axial loads - which are crank killers.

That said - both P and T5 fly side bearings are 15mm deep - and I don't have the space for that.
VBB's came with 12mm deep bearings.
Cure? source a 12mm version of the T5!
It's called an NU 1005 (thanks for the NU lead Safis).

Taken me a while to get here - but really not that complicated.
T5 style bearing on fly side removes pinching of crank.
Retainer on clutch side keeps bearing for moving.
If crank locks in to main bearing properly - this thing might work.

See below.
¯\_(ツ)_/¯

A disappointing crack However, with your antipathy of caution, I would guess you are welding the diet T5 roller (very cool btw) spacer permenantly into the side casing and probably penetrate the crack at the same time (enough with the sniggers...). Has the makings of properly good this time. Crank surrounding gap expected to work out ok?

Precisely.
I stopped yesterday to consider how best to execute.
Realized there is an opportunity here to "line bore" even though I don't have a line boring machine.
It involves some sacrificial epoxy.
Today should be a fun one.
See how it goes. Tru - really does write itself.
This is how Robert Plant must have felt in the early 70's.
I overheated a really thin area - and then pounded the bearing in.
Started as a small crack - and just grew.
Wiser for the experience now...

"A Disappointing Crack"

There is more than enough material here for a new Led Zeppelin album. Or Spinal Tap.

Definitely Spinal Tap, because this project has already gone to eleven.

Those cases have sure been through a lot. I'm not surprised that they would crack. I would imagine that when you are satisfied with your results you would start again with a fresher case.

Looking good, knew you could do it! Shame about the crack, but what's a little more grist for your mill when you've ploughed through a cubic metre of the stuff anyway?

Is that a smallframe bearing or something else? No issues getting a seal I guess.

Caused some chuckles ^^^
Also - Much appreciate all the good comments.

Chandlerman has been providing me P motor insights on the side.
Ginch - in all likelyhood - the bearing I found would fit a smalley.
There are only so many std. bearings as it turns out.
Once Safis turned me on to "NU" style bearings - I just did a search to see if there was a 12mm wide one.
This is it.

They are pretty cool.
Thick roller bearings - look like they are made for a tank.
Specs say 18,000 RPM max.
I should be ok...

Project has moved into a fine tuning stage.
Drawing on what I experienced from some of my wipe outs.
Some pics below:

nice thinking outside the box!

let me know when you want to try your hand with machining barrels and pistons and profiling heads... I have a whole bunch of "practice material"

close, or sort of... the smallie uses a NU204 (basically a baby brother) or more aptly, can use the NU204. the common or more standard is a 9-series single piece ball bearing style. I wanna say 90025?

arguments abound about which is better/more robust/etx

yeah me too Shotgun!

I'm using a new NU204 in my fresh Polini 130 build. Went this route because I like the separate ring on the crank, and ease of assembly. Specs look good too. I'll report back. so far so good, although it not even broke in yet

hahah - y'all are gonna have to wait until my wife's deferred honey-do list is complete.
She's been patient...

So about that idea I had for signing everything up.
I've put so much heat and cutting to these cases - I figured the crank would not be very well aligned.

So I tried my hand at truing my crank - which made a great picture but didn't manage to actually improve it at all - and then got on with putting the adapter in my fly side main bearing.

The concept - now curing in the garage - was to undercut my adapter slightly. so it had just a skosh of play.
Why would I want the main bearing to sit firmly in an adapter that moves around?
Well - I figured that if I undersized it - and used some epoxy - when I closed the cases - it would self align.

So I did.

Plan is to come back and weld the perimeter.
Pictures tomorrow will explain.
But for now - the cases are curing with the adapter in perfect alignment and the crank spinning ever so freely.

While I was at it - I simultaneously bonded in the inlet pad (#4 or 6 or something. I've lost count). That's curing too.
Here are a few pics.

Edit - left this one out - tho perhaps I should have taken the win by doing so.
Couldn't seem to get the readouts to make any sense.
I have two different increments on the gauges - so that added to the calamity.
Save this one for my next build.

The alum heat plug is a great idea

Looks very clever. However, not usual to true a crank this way. Running on knife edges with the gauges outside.
The measurement differential appears to be the same but the reality would exactly as you proved. Confusion.
Like how it all goes together. Running by the weekend.

Checking in with a short update and soliciting some opinion.
Subject: fly side bearing.
Readers of this post may know - I've sourced a roller type baring (NU1005) for the fly side.
Jr. version of the T5 roller - as Jack coined it.

Having inserted and removed it a few times - im dubious of the quality of the one I sourced.
That's a manufacturer issue - not a design issue.
Chinese rather than Japanese bearing quality.

Have a higher quality one lined up - would cost some time until it arrives.
While I wait - toyed around with another idea.
Took a stock VBB ball bearing - and used my newly made precision grinder to take about .01mm off the ID - to make it a slip fit.
Tempted to go this route.
Crank would slip in and out of the fly side bearing - taking pressure off the crank webs.

Suspect that with time - the steel on steel of crank journal and bearing inner - though slip fit - might wear quickly.

Anyone want to pontificate on that?

I think you hit on the issue, your making the crankshaft a slip fit and a wear surface. Normally a surface like that would be well lubricated. Like a crankshaft on a car or cam shaft bearing.

My initial thought was that I agree, but with a little more thought...I don't know...

Assuming that the bearing is spinning freely, the rotation should be handled by the bearing, as-intended. The axial float is probably enough prevent the axial pressure from putting excess stress on the bearing itself or the big end pin/crank webs.

What I *don't* know is whether or not that slip fit will allow too much vibration, which would lead to excess wear on the crank or not.

Too much could/should/would in my thoughts, not enough can/will, but that's the nature of experimentation--develop a hypothesis, figure out how to test it, observe the results.

Personally, I'd give it a shot.

I don't have a clue, but normally I'd throw away a bearing if it had worn down to a slip fit. Deliberately making one into a slip fit seems counter-intuitive, but again, what do I know. Carry on.

Little belly laugh on that one.

If you look at the P engines - they use a press fit bearing on the clutch side - so when you pull the clutch the crank remains in position relative to the rotary pad.
They also have a circlip locking that bearing in place - so it doesn't move inboard either.
Fly side has needle bearings that act as a slip fit.

Making your bearings slip fit is also a tuner's trick for more HP.
However - there is some wear introduced.
Have it in my mind that I am going to get this thing back on the road this weekend.
Will probably go with the roller bearing I already sourced.
Also imperfect but will introduce less wear to the crank.

Been buried with work all week.
Back to my zen place in the garage this morning.

please put in your parts requests early, late night/early bird pick up is available.

Uncommonly good hours of operation…

makes up for the level of service and randomness of inventory!

kajits house of wares: the parts ain't great but we give you a whole lot of 'em. open late!

Repeat customer here, (The mail-order service is legendary.)

Whole lot of junk is better than no junk at all. Kajits house of wares never disappoints

Didn't quite get there.
Took a side road on a seal for the xmas tree shaft.
What's that you say?
Seal for the Xmas tree shaft?
WTF is he talking about?

My motor has always "wept" from where the Xmas tree shaft exits the cases.
Saying "wept" like Greasy taught me - made me feel better.
But I hated the drips of oil.

So before I tackled the fly side bearing - I machined up a little collar with O ring.
I also installed the fly side bearing and adapter.
Decided to bond it rather than weld it.
(actually - I welded it last week - then cut it out and re-installed it with epoxy).

The TDS for the epoxy I used (Saint's is using) on my pad says its thixotropic.
That sounded cool - so I looked it up.
Best I can tell - means it kind of liquifies when it receives stress.
Not sure that's what I want on my main bearing - so I went with SoCal's suggested EA 9340.
Mostly because its also better with heat - and if I ever want to serve the bearing - I need to be able to put a few hundred degrees to it.

Method was to apply epoxy - then assemble cases - so that it would float into position for curing - and be fully aligned.
We'll see.
Still not happy with the quality of the bearing I have - but that is always replaceable.

Its looking so good on the flywheel side...!

Looking forward to the first kick!

Yeah - but jeez - my grill cover really needs to be cleaned!
(thanks)