Model Engine Maker

Help! => Specific Engine Help => Topic started by: Frank Boyle on January 25, 2016, 08:44:00 AM

Title: Centaaur gas engine
Post by: Frank Boyle on January 25, 2016, 08:44:00 AM
Hi all
I have been having a problem with the cylinder liner which is cast iron.On the mold joint and both end it was chilled.After boring the liner was slightly oval where the boring bar had flexed over the chill areas.I have spent hours lapping the bore and have got it to within 2th" I want to finish with a cylinder hone to remove the glass finish from the lap .Is 2th" near enough or have I got to carry on lapping.
Frank
Title: Re: Centaaur gas engine
Post by: Manorfarmdenton on January 25, 2016, 10:13:59 AM
Frank, you have my sympathy!  Its just the sort of thing that happens to me.  I can't help but I'm very interested to see what those with experience will say.  There's a huge amount of collective knowledge on this forum!

Kind regards,
John.
Title: Re: Centaaur gas engine
Post by: Alyn Foundry on January 25, 2016, 02:33:16 PM
Hello Frank.

I'm not familiar with the Centaur engine is the liner a cast Iron tube?

Chilled cast Iron can be a nightmare, as you're left with the Silicon the carbon having migrated to warmer areas during the cooling process. In fact, for certain applications a " Chill " or " Denser " can be placed within the sand mould to produce just that effect. Certain engine manufacturers used this to produce a harder cylinder bore.

Have you tried to anneal the casting? Sometimes heating the casting up to bright Orange then burying it in warm sand can redistribute the Silicon/Carbon mix.

For the most part our moulds were poured in the afternoon and only opened the following morning reducing the risk of a chill immensly.

Kind regards, Graham.
Title: Re: Centaaur gas engine
Post by: Manorfarmdenton on January 25, 2016, 05:29:39 PM
John Deere, the blacksmith who was to become a household name (in farmhouses anyway...) pioneered a way of putting cast iron below the sand in his plough share moulds, producing a cast share with a hard layer underneath which had the effect of making them self-sharpening.  I think......

John.
Title: Re: Centaaur gas engine
Post by: Jasonb on January 25, 2016, 05:34:49 PM
Frank is that 0.002" or 0.0002? if its the later then you will probably get away with it if it is two thou then I would say you need to do some more lapping.

I prefer to make cylinder liners from continuously cast bar as its nice and consistant.
Title: Re: Centaaur gas engine
Post by: Frank Boyle on January 26, 2016, 06:33:47 AM
Thanks for your replies, it is 0.002" Jason so back to the grind.I will not buy another casting of a cylinder but do as you do and buy cast bar.The liner fits the water jacket so well that I will continue .
Frank
Title: Re: Centaaur gas engine
Post by: Frank Boyle on January 27, 2016, 06:33:12 AM
After four hours of honing my fingers are hurting,but I have arrived at a cylinder and am going to make a plug guage before starting on the piston.My concern is that I used grinding paste to remove the chilled areas and am worried that some might have become ingrained in the cast.Although I have used thinners to clean the bore and washed it in soapy water. What is the best way to clean it.
Frank
Title: Re: Centaaur gas engine
Post by: Jo on January 27, 2016, 08:06:53 AM
I use brake cleaner then boil it in a pan of soapy water.

Jo
Title: Re: Centaaur gas engine
Post by: Manorfarmdenton on January 27, 2016, 10:54:40 AM
I agree with Jo about the brake cleaner.  I use it a lot.  Hot soapy water and a toothbrush after the brake cleaner would be good too.  John.
Title: Re: Centaaur gas engine
Post by: Roger B on January 27, 2016, 11:25:53 AM
An ultrasonic bath is also a good option if available.
Title: Re: Centaaur gas engine
Post by: Frank Boyle on January 27, 2016, 05:32:18 PM
I have not got access to an ultrasonic bath but I am off to buy some brake cleaner,I shouln't have any trouble with the soapy water, washing up is my province.Thanks for your help.
Frank
Title: Re: Centaaur gas engine
Post by: Manorfarmdenton on January 27, 2016, 06:51:08 PM
<<washing up is my province>>  join the club  :)  John.
Title: Re: Centaaur gas engine
Post by: Jo on January 27, 2016, 07:41:43 PM
You need to boil it as well for a good 5 mins ;)

Jo
Title: Re: Centaaur gas engine
Post by: Manorfarmdenton on January 27, 2016, 10:44:26 PM
You need to boil it as well for a good 5 mins ;)

Jo

I thought that was what dishwashers were for  :) 

John.
Title: Re: Centaaur gas engine
Post by: zeeprogrammer on January 27, 2016, 11:09:04 PM
<<washing up is my province>>  join the club  :)  John.

It's worth it...no?

Yes.
Title: Re: Centaaur gas engine
Post by: Frank Boyle on February 03, 2016, 09:30:02 PM
Started the piston and again am dogged with chilled cast iron.I took up Grahams advice and put the casting into the fire for hours and then cooled in some kiln dried sand.The chill seems to now have migrated to the skirt of the piston and is proving a b*****d to machine.I am using a TC tipped tool
but it isn't cutting well for the first 1/2".I am open to any advice that sugests a solution to this problem.The only  alternative I can think of is to get a piece of bar and start again.This I don't want to do if I can avoid it.
Frank