Author Topic: Machining bores of Hoglet engine  (Read 500 times)

Offline Trevorc

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Machining bores of Hoglet engine
« on: July 16, 2017, 05:24:21 PM »
Hello, once again i am seeking some advice or guidance.
I am about to start machining the cast iron cylinders for the Hoglet. I had planned to use what i thought was the accepted method- bore to about 2 thou undersize and finish using diamond paste and an expanding brass lap. However I discussed this with a friend ,whose engineering opinion i usually respect, and received an emphatic NO. He argues that the diamond will embed withing the cast iron as well as the brass thus causing problems later. He advocates boring to finish size and polish using one of those spider like, three stone, brake cylinder hones.
Can anybody please give me some further input. Is my friend correct?
Many thanks.

Offline Jasonb

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Re: Machining bores of Hoglet engine
« Reply #1 on: July 16, 2017, 05:34:52 PM »
Are you going to use O rings as per drawing or opt for cast iron?

O rings will be better in a lapped bore in which case use silicon carbide powder and oil with a brass or copper lap. If using iron rings then as your froiend says a sprung brake cylinder hone will do teh job

Offline Trevorc

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Re: Machining bores of Hoglet engine
« Reply #2 on: July 16, 2017, 05:39:00 PM »
It seems that most people use cast iron rings so that is the way i was going.
Trevor

Offline mikecole7

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Re: Machining bores of Hoglet engine
« Reply #3 on: July 16, 2017, 06:04:10 PM »
Hi
    I have made a few cast iron barrels and I use cast iron rings . I bore to size and then clean the machining marks off with a brake cylinder hone , seems to work for me.



     Mike
     

Offline Walsheng

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Re: Machining bores of Hoglet engine
« Reply #4 on: July 16, 2017, 09:07:37 PM »
Just remember, diamonds are forever!
We use diamond paste to polish molds but never to lap out a hole for a sliding pin.  And most pins would see far fewer cycles than even an infrequently run model piston.

John

Offline Nick_G

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Re: Machining bores of Hoglet engine
« Reply #5 on: July 16, 2017, 10:25:35 PM »
.
When making my Hoglet based engine I bored them out and finished them with a sprung 3 stone cylinder hone. I made cast iron rings and all was well.

Link to my build log if interested. http://www.modelenginemaker.com/index.php/topic,5947.0.html

Regards,  Nick

Offline gldavison

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Re: Machining bores of Hoglet engine
« Reply #6 on: July 16, 2017, 10:48:28 PM »
I used a brake hone on my cast iron cylinders. That was 4 years ago. My engine is still running on the first set of o-rings, and has awesome compression. It get a lot of attention at the shows and I run it a lot.

http://www.gldpages.com/Video/Hoglet.mp4
« Last Edit: July 16, 2017, 10:52:02 PM by gldavison »

Online b.lindsey

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Re: Machining bores of Hoglet engine
« Reply #7 on: July 16, 2017, 11:10:00 PM »
Another vote for the brake hone, especially if using cast iron rings.

Bill

Online Hugh Currin

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Re: Machining bores of Hoglet engine
« Reply #8 on: July 17, 2017, 01:02:01 AM »
How about Time Saver Lapping Compound? It is made to break down so would not embed in either surface for long. Their Green compound is advertised for cast iron.

I don't know how well it would work. I'll be interested in any responses.

Thanks.

Hugh

Offline Ian S C

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Re: Machining bores of Hoglet engine
« Reply #9 on: July 17, 2017, 10:57:57 AM »
I too would like to know how effective Time Saver is for lapping cylinders.
I use at times the 3 stone brake cylinder hone, and for lapping, an expandable wooden lap with fine(not sure of the grade) grinding paste(too fine really), I have used tooth paste, and Brasso.
Ian S C

Offline Roger B

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Re: Machining bores of Hoglet engine
« Reply #10 on: July 17, 2017, 07:42:25 PM »
I have used Diamond paste and a brass barrel lap for lapping cylinder bores, but you need an ultrasonic bath to get the Diamond residue off.
Best regards

Roger

Offline crueby

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Re: Machining bores of Hoglet engine
« Reply #11 on: July 17, 2017, 08:32:46 PM »
I used Time Savers on my last two builds, worked great. I had gotten their sample pack of the different grits, the small sampler is a lifetime supply for this use.