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Feb 09, 2019, 05:22 PM
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Question

OS Wankel PI-2 side housing re-finish


Hello, all. I hope someone can help with information about the side covers on the latest OS Wankel. I have a newly acquired example, and has seen almost no run time. Unfortunately, a small metal shard was wedged between the rotor and side housing. It only took a few full revolutions of the crank by someone in the past to gouge a .25mm epitrochoid channel in the aluminium side housing. I have heard that some have milled the side housings flat, and ended up with a running engine. However, another forum post stated that the wear surface on the aluminium housings have a surface coating that, if removed, will wear out the housings in no time. I've come up with nothing concrete either way, and I figured that as they are, I can't use them, so not much to loose by milling them flat. Any info about the surface coating would help, or if anyone out there has successfully re-surfaced the housings, that would help too. Thanks!

Rhys Legge
Last edited by RLegge; Feb 09, 2019 at 07:45 PM. Reason: Thread type change
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Feb 09, 2019, 08:23 PM
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gkamysz's Avatar
I happen to have one apart on my desk. I don't see any coating on on the running surface, but it does appear to be ground.

Greg
Feb 09, 2019, 09:43 PM
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I haven't seen the coating on either my PI or PI-2, but I know industrial coatings can sometimes only be molecules thick. For now, I ordered a .0001 flat marble machinists block, and will proceed with surfacing the housings using paper, probably down to 2000 and see how it goes.
Feb 10, 2019, 01:54 AM
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Quote:
Originally Posted by RLegge
I haven't seen the coating on either my PI or PI-2, but I know industrial coatings can sometimes only be molecules thick.
Doubt that those coatings were applied in stuff like model engines back when those Wankels were produced...
Feb 10, 2019, 10:50 AM
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Quote:
Originally Posted by Brutus1967
Doubt that those coatings were applied in stuff like model engines back when those Wankels were produced...
Good point, I work in aerospace and I can see your point, not everyone has the budget of Dassault Falcon especially in the hobby industry.
Feb 12, 2019, 08:04 AM
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The "surface coating" is a type 2 hard anodize. Do not machine the surface. The anodize is only a few microns thick.
Feb 12, 2019, 08:47 AM
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If the housings are in fact hard anodized that process should be available from several vendors. I'd bet a google search would turn them up.

Ken
Feb 12, 2019, 10:12 AM
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Quote:
Originally Posted by Fox35
The "surface coating" is a type 2 hard anodize. Do not machine the surface. The anodize is only a few microns thick.

Type II is not hard anodize. Hard anodize is rarely thin. OS aluminum carb rotors are hard anodized. The running surface of the housings is dead soft and the same as the other surfaces. Castings are not typically anodized. There is no load on the faces of these parts with no side seals on the rotor. If there is some coating, running the engine wears right through most of it.



The very first versions (~1970) of the Wankel had steel sprayed onto the aluminum housings. They stopped that after a year or two.
Feb 12, 2019, 12:38 PM
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Quote:
Originally Posted by gkamysz
Type II is not hard anodize. Hard anodize is rarely thin. OS aluminum carb rotors are hard anodized. The running surface of the housings is dead soft and the same as the other surfaces. Castings are not typically anodized. There is no load on the faces of these parts with no side seals on the rotor. If there is some coating, running the engine wears right through most of it.



The very first versions (~1970) of the Wankel had steel sprayed onto the aluminum housings. They stopped that after a year or two.
I do type 2 and type 3 sulphuric anodize processes on military aircraft. Castings and forging. Just saying
Feb 12, 2019, 01:18 PM
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gkamysz's Avatar
Quote:
Originally Posted by Fox35
I do type 2 and type 3 sulphuric anodize processes on military aircraft. Castings and forging. Just saying

Yeah, I know castings are sometimes anodized. If these engine parts are anodized, I'd be extremely surprised, there are no signs of it at all. How did you determine these are anodized?
Feb 13, 2019, 02:53 PM
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Continuity test
Feb 13, 2019, 04:16 PM
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gkamysz's Avatar
Mine checks out to a dead short. Which version of this engine did you check exactly? Mine is the first PI, but the later Type II lists the same part numbers.
Feb 14, 2019, 07:51 PM
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Wow, thank you to all who have chimed in on this! It does appear that there is no surface treatment on the PI-2, but I wonder if I tried to contact OS directly they could confirm or deny this. I will attempt, at the very least.
Feb 14, 2019, 07:57 PM
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They answered a couple of my questions promptly.
Feb 15, 2019, 09:40 AM
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kenh3497's Avatar
I would think a hard chrome or nikasil type surface would be nothing but good on the side covers. Finding somebody to do it would be the issue. At a reasonable price that is.

Ken


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