hey donp .. how about this..

as far as turning the rope-trick into a salable product.. how about this..

it's got a spark plug thread (14mm popular enough?), basically a long rod, padded on it's end. Screw it into the plug hole (maybe has a ball or T-handle for easy insertion) and it jams the piston at mid-stroke... see pic.

1118767789_thing.jpg

Re: hey donp .. how about this..

Don Pflueger /

that would work but they already make and sell piston stops similar to that.

Re: hey donp .. how about this..

Steamboat Aka J. R. Stevens /

Re: hey donp .. how about this..

Joe Woods /
joew OP

well.. that figures, since the idea is kinda obvious.

I could see molding it in one piece plastic for a few pennies.

Re: hey donp .. how about this..

Jason Luther /

i say the rope is unbeatable

Re: hey donp .. how about this..

Smitty Smith /

I've used the rope piston-stop idea several times since DonP posted it. I've only had it _hang in a port once_. learned my lesson, now I bring the piston to TDC, then back down a little, and insert rope...avoiding the aggravation of getting it caught in a port window.

rope ain't always dope

Rope sometimes can get caught in transfer ports and jam up your piston, as it happened on my Grande. Had to melt it apart. Also, you can get it dirty easily and get crap in your cylinder. I still use it, but I'd like a real metal piston stop. Not sure how well a plastic one would work.

Re: rope ain't always dope

Joe Woods /
joew OP

if you used an engineering polymer, like the stuff they make gears from (maybe an acetal like Delrin) it would be plenty strong enough, but cost would be higher. They have replaced lots of metal parts with that stuff. A few prototypes and some testing would reveal the most suitable, lowest cost material.

One good thing about using plastic is no danger of stripping the plug threads... and by it's soft nature plastic is already "padded".

But the rope is more of a universal tool.. a tool that needs a particular thread is limited in application.

Maybe there's a way to temporarily secure the piston stop without using the plug's threads.. some kinda expanding mechanism...

Re: rope ain't always dope

Don Pflueger /

lol. joe, your over thinking simplicity.

Re: rope ain't always dope

Joe Woods /
joew OP

you're right .. thanks for pulling me back from the edge of the anal-retentive twilight zone.

Re: rope ain't always dope

Don Pflueger /

lol

Re: rope ain't always dope

Where's the post for the rope trick? Does anyone know off-hand?

Re: rope ain't always dope

Joe Woods /
joew OP

'search' for several threads about it in this forum.

To prevent the crankshaft from turning so you can remove a nut or whatever, slip a short length of soft rope into the spark plug hole.. this blocks the piston as it rises with a soft pad and prevents the crank from tuning further..

Don't let the rope extend into a port as it may get jammed bad between the port and piston.

Re: rope ain't always dope

wooden dowel with 14 mm threaded adapter break porclin out of bad spark plug drill out plug body put 1/2" or so dowel in drill small cross hole mount at proper location for TDC put bolt inplace wala piston stop.Jim

Re: rope ain't always dope

Joe Woods /
joew OP

i like that .. gonna try it, maybe with some epoxy and an aluminum rod intead of the dowel. One thing though..

I'd want to stop the piston at mid-stoke. The crank and rod angle is greater here and upward piston force will be minimal.

Near TDC when the crank/connecting rod straightens out, toggle forces will be huge.. (same goes for BDC) They make very powerful clamps based on this toggle joint idea.

Re: rope ain't always dope

Hi joew,

The only reason I suggest a hard wood dowel is cheapness and above all softer than the aluminum piston another aluminum product against the piston makes me nervous any scratches ect. and more carbon buildup and less compression.if the crank shaft was at an angle wouldn't it be more likely to bend the connecting rod trying to remove that rusted on flywheel nut??? maybe I'm just not thinkin it through right.but anyways if you had it set at TDC you could use it for setting timing ect. have different adjusting holes for different purposes.This from someone who doesn't know much about 2 strokes laugh.never mind.Jim

design

Joe Woods /
joew OP

the basic idea makes me nervous ..it always did.. even when using the rope. There's something about applying forces backwards (instead of the piston turning the crank, it's reversed) that bothers me .. but people do it and it works ok.

I mentioned an aluminum rod just because i've got some 1/2 inch stuff laying around. It's soft, drawn aluminum, and not near as hard as the piston alloy. But using anything less than a soft, wide cushioning pad like that afforded by a piece of rope, even a wooden dowel, seems a bit harsh.

For use as a piston stop to wrench on the crankshaft, i still think stopping it at mid stroke is best. It would be easier to break the tool or damage the rod bearings if the stop is near TDC for the reason i spoke of... forces against the tool will be highest near TDC. That small crank pin / connecting rod angle affords lots of leverage. Bearings and the piston itself seem more vulnerable than the rod.. but who knows..

As for a tool to detect TDC nothing beats a dial indicator, imo. The back and forth movement of the dial's needle lets you zero-in on true TDC. Changing something like head gasket thickness doesn't matter to the dial indicator.

this thing's a work in progress.. hashing it out on paper and in the brain saves a lot of effort. Adapting a old spark plug seems like a good basic idea to build on.

Re: design

Yeah I will build one but not use it because it makes me nervous to stop the piston to remove nuts ect,But it has worked.I use a spanner wrench used to remove grinding wheels.I bought it at ace hardware for 3.99 it's made of 16 gauge steel about 3/4" wide and 7" long with a shorter piece rivited near the top. The top ends have studs that go into the holes in the flywheels spokes. It can be expanded to reach further apart holes.

It looks like a Y more or less works good to hold flywheel while i remove the nut.Jim

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