Author Topic: alloy casings  (Read 176 times)

Offline marty 31

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alloy casings
« on: November 27, 2019, 06:47:00 PM »
can I ask for advice on polishing alloy engine casings please, I have seen lots of lovely polished casings and realise theres a lot of elbow grease required but any advise would be appreciated

Offline cardan

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Re: alloy casings
« Reply #1 on: November 27, 2019, 09:20:56 PM »
Polished crankcase castings were pretty rare in any era, other than on modern glitz restorations.

There are a couple of reasons.

The first is that, as you say, it takes lots of effort and would be expensive for the manufacturer.

The second reason is much more practical. A polished aluminium surface has an emissivity 5 to 10 times lower than oxidised aluminium: in layman's terms highly polished aluminium is no good at all radiating heat. Almost any other finish to the cases - leaving them rough cast, bead blasting, anodising or even painting - will allow heat to radiate faster from the cases and leave you with a cooler-running engine. This is why cylinders and heads are never polished or plated.

Personally, if a set of cases is in "as cast" condition but grungy, I just deep clean them using degreasers, alloy wheel cleaner, detergent, hot water, and nothing more abrasive than a green ScotchBrite scourer. Some people like to bead blast, or "water" blast (which usually still has abrasive particles in the water stream), but I avoid this on engine parts if I can. That way i don't have to worry about the abrasive particles that find their way into every nook and cranny.

Have fun.

Leon

Offline john.k

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Re: alloy casings
« Reply #2 on: November 28, 2019, 10:55:24 PM »
If you want the easy way ,get your cases wet bed blasted......and make sure the operator is using new bead.......IMHO its best to find someone with both wet and dry processes ....the worn wet bead can then be used up in the dry blasting process,rather than left in the wet machine until its dust.......A blast with new bead will produce a lovely dull sheen,obviously not OEM,but very nice to look at...

Offline marty 31

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Re: alloy casings
« Reply #3 on: November 30, 2019, 06:08:09 PM »
Polished crankcase castings were pretty rare in any era, other than on modern glitz restorations.

There are a couple of reasons.

The first is that, as you say, it takes lots of effort and would be expensive for the manufacturer.

The second reason is much more practical. A polished aluminium surface has an emissivity 5 to 10 times lower than oxidised aluminium: in layman's terms highly polished aluminium is no good at all radiating heat. Almost any other finish to the cases - leaving them rough cast, bead blasting, anodising or even painting - will allow heat to radiate faster from the cases and leave you with a cooler-running engine. This is why cylinders and heads are never polished or plated.

Personally, if a set of cases is in "as cast" condition but grungy, I just deep clean them using degreasers, alloy wheel cleaner, detergent, hot water, and nothing more abrasive than a green ScotchBrite scourer. Some people like to bead blast, or "water" blast (which usually still has abrasive particles in the water stream), but I avoid this on engine parts if I can. That way i don't have to worry about the abrasive particles that find their way into every nook and cranny.

Have fun.

Leon
thanx for the advice, I think I maybe wasn't perfectly clear, when referring to casings, I was referring to the clutch, and timing side ones that originally had been smooth and shiny when the machine had left the factory, I know hard graft and autosol polish, works but leaves the deeper scratches, can you use say steel wool or emery cloth first before polishing? can polishing wheels say in a drill help? before hand polishing, I have seen many engines that highly polished one would nearly think they had been chrome plated, that's the look I desire

Offline Mark M

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Re: alloy casings
« Reply #4 on: November 30, 2019, 06:20:17 PM »
I understand if you want to do it yourself but if you want a "show" finish it is time consuming and expensive (materials and equipment,) and needs practice and skill. A professional might be the best bet. This guy is recommended, Brightworx, (near Lincoln,) 07498 681023. I do my own polishing but I'm aiming for a "Factory" level of finish (Royal Enfields that is,) which after a lot of effort and practice I can manage.
REgards, Mark

Offline marty 31

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Re: alloy casings
« Reply #5 on: December 01, 2019, 09:10:20 PM »
a factory finish, would be all that's required, I am tempted to send them to the guy you recommended, think I will try by myself first, thank you for your advice and I will keep posting about any results