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Post by eddy on May 4, 2015 18:03:02 GMT
This will hardly be a project, but I thought it might be of interest to someone, that is if it all works out. I split my engine after a serious breakdown, and found a few broken teeth on both my 3rd gear and christmas tree. Cruciform also had a broken arm (I did too, at the time). So I finally got around to ordering everything I needed (or so I thought) from sip: all that was broken, plus all seals, bearings, o-rings, rubbers etc. Came out a bit more expensive than I hoped for, but I didn't really have a choice. Then when I continued breaking down the cases to have them both 100% ready for fitting bearings and seals and such, I found this:  The red circle shows all that is left for the circlic on clutch basket side to hold onto. Needless to say it didn't sit quite right wen I took it out. Funny thing is that I didn't find any traces of aluminium inside the cases, only steel which was clearly teeth from gears and cruciform. This means I have been driving around for over two years before things have gone wrong...! Anyways, I have an appointment with a very good welder (so I'm told) on thursday, and after that I will take it to work to have the slot remachined. If the welder is not too expensive I will have him add some meat to the cases so I can do some proper porting either now or in the future. This brings me to a question actually. I'm wondering how much of an improvement I will get from match porting my cases to my Polini 130? My current set-up is: Polini 130 Sito banana 24mm PHBL Vespatronic ignition Standard cases. Updates to come soon! |
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Post by vader19 on May 5, 2015 0:02:09 GMT
Is it just me? but that looks like someone used a tool to grind the rest of that lip away.. on purpose. ?
Why would they do that.. it doesn't look broken off at all, but ground off instead.
Regarding the matching of your case to the cylinder.. I can't say how much for sure, but I'm definitely a fan of doing so.. just imagine yourself as the air/fuel mix and how you'd want to travel through the cylinder and case.. IIWY, I'd match it.
That circlip lip is very strange.. it's a head scratcher for sure.
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Post by eddy on May 5, 2015 8:48:07 GMT
If I had taken a better picture, you'd see that it looks very much like a brittle fracture. It still doesn't explain why I didn't find any aluminium pieces inside the casings though.
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Post by eddy on May 5, 2015 8:50:42 GMT
Found a slightly better one  |
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Post by triffid on May 5, 2015 11:47:31 GMT
I'm not sure I would persevere with that tbh, you would probably be as cheap getting hold of a secondhand half casing, I'm sure someone on here would have one. While it might be an engineering challenge to get it welded and then ground and a new slot cut into place is it really worth the effort and risk of it never being quite as strong as it should be.
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Post by robd on May 5, 2015 12:07:08 GMT
I've had a similar repair done on the driveside bearing lip on a lambretta casing and the circlip groove is just another machining step. As mentioned above though, it won't be a cheap exercise and so a replacement case would make economic sense.
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Post by eddy on May 5, 2015 14:05:41 GMT
The machining will be free, and let's say I could need the addition to the side of the casing for later porting anyway  Also, I can't see why it would have to be very strong, clearly something brutal has happened to it before, but during driving it shouldn't see side loads at all, as far as I can tell... Could I use a spare PK half casing? I have a complete PK motor, but I was hoping to keep it complete until the day I take on the task of restoring another smallie I have. |
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Post by jeanshorts on May 5, 2015 15:31:03 GMT
Might bearing retaining compound be up to the task?
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Post by vader19 on May 5, 2015 17:31:03 GMT
You're right eddy... the tighter picture tells a different story.. as far as the aluminum bits go.. they probably turned to dust..
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Post by eddy on May 6, 2015 6:26:35 GMT
Hehe, good thought.
AND good thought with the bearing retaining compound! Might add some of that for that extra safety feel.
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Post by sugarlump on May 6, 2015 7:11:09 GMT
In my limited aluminium welding experience I think where the lip has broken and exposed the rough surface I think all manner of oil and dirt will have leached into casing making job a bastard. I agree with some of the other lads, try to pick up another case, it's not like you've already invested mega £ with previous welding and machining that would make it worth while saving.
On the flip side, if it's not gonna cost you the earth you might as well have a crack. I wouldn't want the job of machining post weld, just clamping the case in plane to a milling machine bed is a nightmare.
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Post by jeanshorts on May 6, 2015 8:38:17 GMT
I'd be worried about heat distortion. If I'm not mistaken all the side load on that bearing is in the opposite direction of that circlip. If it was me it would get a few drops of bearing retaining compound and be forgotten.
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Post by henri on May 6, 2015 14:26:01 GMT
i agree with sugarlump ,the open pores of fractured ali will suck in oil contaminates ,so unless you machine it right back to clean any weld will tend to fracture off along the same plane from inclusions/contamination,
as jeanshorts says ,permanent bearing locker on bearing an circlip ,but these sorts of stuff is never forgotten an lingers at the back of ya mind , new cases for peace of mind alone , H
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Post by tzsteve on May 6, 2015 15:24:09 GMT
looks to me like someone used a hammer to remove the bearing and forgot about the circlip, and the reason you didn`t find any debris in the case is all the rubish was removed proir to him selling it.
that`s just an engineers guess
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Post by eddy on May 6, 2015 20:24:43 GMT
Whoa, didn't expect all those reasons why NOT to try.
About the oil contaminating the pores of the aluminium; if the welder cleans it up really good, maybe grinds it down a bit, and he feels its going OK, then I see no reason why not to trust it. After all, we are welding, not brazing, there's nothing to "loosen" from the casing once it's all melted together.
We'll see tomorrow :-)
Does anyone know if a could fit a PK casing half instead of the 50s one I have now?
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Post by tzsteve on May 6, 2015 20:29:29 GMT
i thought they were the same except for the ets flywheel side bearing and a couple that have the 3 stud manifold
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Post by jeanshorts on May 7, 2015 1:50:28 GMT
I feel like I should qualify my advice as assuming you will be running straight cut gears. I'm not really sure which way the helical gears load that bearing.
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Post by triffid on May 7, 2015 11:25:50 GMT
The real thing to consider here is, if a bit does break off after welding, it is going to d a lot of damage to your internals and probably lock up your engine and chuck you off it. Lots of pain all round. Is it really worth the risk of the cost of a second hand case?
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Post by eddy on May 7, 2015 17:08:04 GMT
Just came back from the welder. He did a really nice job, and he was confident that it went well. He ground back the material and tried until he felt the welding was going super smooth. He also said the alloy was really nice to work with, compared to most car/motorbike stuff people bring him. He was not worried about distortion either, except he told me to double check the gasket face for the cylinder. I know some of you guys are wondering "why take the risk", but I do not think there is much of a risk, not as long as I leave everything to the pros. How do you even calculate that there is a risk? Second, I think it's super fun to salvage parts that most people would give up.    |
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Post by tzsteve on May 7, 2015 17:20:29 GMT
aint welding a wonderful thing.
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