Tool post grinding wheel dressing apparatus

[rgray]

. The link I provided in post#12 talks about how hes sets up using defined mandrels.

Wow that's a long thread. looked it over more. You must mean post 121 ? I searched for what you were referencing but didn't find it on post 12.
In 121 he's talking about the taper on a piston. All pistons are tapered as the top expands with heat and grows.

 

[petertha]

Sorry for any confusion. I referenced the ModelEngineMaker link in post #12 of this Hobby Machinist thread. Anyways in that MEM reply #121 he says
The piston's circumference at it's top is tapered for use in tapered cylinders.

more info page 27 this link

Propwash April 2019 web.pub

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namba.com

general info

Tapered-Bore Engine Break-in - Upgraded - RCU Forums

Glow Engines - Tapered-Bore Engine Break-in - Upgraded - This issue is revisited time and time again by many modelers. Every week, or two, another modeler opens a new thread, asking questions about this subject. I have referred many of them to the original thread. Since the original thread was...

www.rcuniverse.com

I'm not an 2-stroke engine designer & my experience is limited to RC (methanol burning, glow plug ignition, quasi-dieseling) stuff which may operate at different principles & rpms to larger displacement engines. I've heard of different permutations in RC depending on applications: tapered liner + tapered piston, tapered liner & cylindrical piston. Supposedly part of the pinch point magic is the piston effectively molds into a resultant slight barrel shape during break in. But even if they replicate the shape to begin with, it doesn't work. I'm sure there is a wealth of knowledge out there. Heck, if I still had the engines I would just measure them LOL.

 

[rgray]

Sorry for any confusion. I referenced the ModelEngineMaker link in post #12 of this Hobby Machinist thread. Anyways in that MEM reply #121 he says
The piston's circumference at it's top is tapered for use in tapered cylinders.

Yep ...I missed that. Guess I should have put more powerful readers on. lol The type is small on that site.
The propwash info shows honing on a sunnen hone machine. Truing sleeves are used to "square" the hone abrasive square and flat.
Maybe they make their own truing sleeve with the taper to true the stone in a taper. Interesting stuff.

 

[petertha]

I've wondered about that. Do the Sunnen cutting stones get dressed so the corners do the cutting until they wear down a bit on the bore?

I've visualized different ways to make an expanding arbor & even found some skinny abrasive stones sticks. But the real trick is the micro wedge adjustment to on the fly to incrementally increase the cutting diameter. I guess that's why they developed Sunnen's to begin with.

 

[rgray]

Dressing the stones is is done with a hardened truing sleeve so they are dressed rounded.
Just one stone per mandrel. Or stones on one side maybe I should say.
There are many variations of stones when getting into larger and longer mandrels.
Two stones lengthwise for longer mandrels is common. Some larger ones have 4 stones length wise, but they are 2 holders
that are wider with 2 stones per holder with some separation between them.
cheaper mandrels are sacrificial, more expensive have replaceable wear pads on the opposite side of the stones, they are usually brass.
A honing oil pump runs anytime the mandrel turns so constant oil flow on the part is normal.

 

[petertha]

I might have been looking at Sunnen portable honing heads at the time thinking they might lend themselves to remote power (lathe) operation. But I still don't have a clear picture of the head components & adjustment process. More research required.