262XP Day

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Marshy

Marshy

285 Killa
Joined
Jan 19, 2014
Messages
6,306
Location
Mexico NY
Well does sinusoidal really describe it? I've often wondered.
View attachment 417948
New+Picture+%28118%29.png

New+Picture+%28117%29.png
Yes it does. It represents position of the piston vs time. When you increase the rod length the wave changes, the piston spends more time near TDC and BDC for a given change in crank angle.

A longer rod ratio produces a more uniform piston velocity throughout its stroke. Thus a long rod produces lower peak piston velocities/accelerations/jerk etc. Generally, intake flow stagnates at sonic velocity. And since intake velocity through the ports is relatively proportional to piston speed, intake flow benefits from reduced peak piston velocity.
Engine design variables like stroke/bore ratios and rod ratios is an excercise in compromise. For low speed engines, a long rod is especially beneficial. It reduces peak piston velocities/accelerations and inertia loads on the rod and crank bearings. A long rod also minimises rod angulation and thrust load/friction losses at the piston skirt.
 
Mastermind

Mastermind

Work Saw Specialist
Joined
Nov 21, 2009
Messages
36,449
Location
Tennessee
Randy,
Without doing the base&squish, just by doing finger and bridge, how much gain do you think that modd would bring?

And second, how close to perfect do you think the timings are on standard 262?

I also have a third question, do your guys now and then shave off the lower transfer a bit, or would it not mather at all?

I'm sure there would be gains.......I have no idea how much though.

For that saw........they are very good. And by studying the port layout of the 262, and considering the timing numbers, I'm sure ideas begin to form.....

Yes?

On this saw I barely touch the lowers.

But I do knock off the lip on many others.
 
Marshy

Marshy

285 Killa
Joined
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Messages
6,306
Location
Mexico NY
No it doesn't.

A sinusoid is perfectly smooth to my knowledge.
Im not here to agrue semantics. If you consider displacement vs angle it is. When I wrote my first response to you I could not see your pictures and didnt realize your graphs were velocity vs angle. It all depends on your perspective.
 
OnTheRoad

OnTheRoad

Collector of shiny things.
Joined
Jan 24, 2014
Messages
614
Location
In my own bed every night. Kansas City Northland
Not just fingers.......fingers and bridges.

View attachment 417960

This is the swarf from the transfer work so far. For visual reference that tool is 7" long with the burr.

View attachment 417961

I'm taking my lovely wife out for Sushi. She's been fasting and this is a great way to break her fast.

Later. :)
Nice work, Randy. What 5 axis cnc mill do you use for those bridge/finger ports?
 
drf255

drf255

BAD CAD
Joined
Nov 3, 2014
Messages
4,114
Location
Socialists Republic of New York
Nice work, Randy. What 5 axis cnc mill do you use for those bridge/finger ports?
I know. They're fricken perfect looking.

The pics of those make me want to return my grinder and just sent all my saws to Randy.

Hence why he openly shares numbers. You can't really recreate.

Like Mozart giving you his music and you buying the same piano as him. You just ain't playing that concerto the same way.
 
SawTroll

SawTroll

Information Collector
Joined
Jan 13, 2005
Messages
64,856
Location
Troms, North Norway
I only check the serial number, 1 is the year, the two next is the week.

That is true, up to and including 1996.

From 1997 to about (haven't found the exact cutoff week yet) week 18 1999 the full year will be on the tag in addition. After that the year code is two digit, and there is one additional extra digit (to make room for more than 9999 saws in a given week - I have never seen that actually happen though).

The 262xp was made at least up to 2005/2006, for some markets (Israel and Russia identified). The last one to be discontinued likely was the 262xph, that was a special for the Russian Siberia market.
 
old-cat

old-cat

Fir Man
Joined
Aug 18, 2012
Messages
3,752
Location
Near Mt. St. Helens
I know. They're fricken perfect looking.

The pics of those make me want to return my grinder and just sent all my saws to Randy.

Hence why he openly shares numbers. You can't really recreate.

Like Mozart giving you his music and you buying the same piano as him. You just ain't playing that concerto the same way.
This is exactly what I was thinking when I said you guys are over thinking. Randy does what he does because he WORKS so hard at perfection. TRIAL and ERROR!
 

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