Author Topic: A "Poppin" Question  (Read 2528 times)

Offline wagnmkr

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A "Poppin" Question
« on: January 05, 2014, 08:13:07 PM »
I was having a look through the Poppin  (Flame Gulper) plans and see that they call for a cast iron cylinder and a steel head.

Is there a special reason why the head has to be steel? Could it be cast iron as well?

Cheers,

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline b.lindsey

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Re: A "Poppin" Question
« Reply #1 on: January 05, 2014, 08:37:46 PM »
Tom, I see no reason the head couldn't be cast iron also as long as it is machined smooth so that the valve flapper seats well against it.

Bill

fcheslop

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Re: A "Poppin" Question
« Reply #2 on: January 05, 2014, 09:15:09 PM »
I used brass on my poppin and there's been no problems.Make the valve from 3thou feeler gauge stock as I found the 2thou tended to buckle.
I also added 1/32 to the cylinder length and made a spigot for the cylinder to locate into the frame other than that she is as per drawings and a good little runner.
Good luck with the build
cheers
frazer

Offline b.lindsey

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Re: A "Poppin" Question
« Reply #3 on: January 05, 2014, 09:29:11 PM »
Tom, though most I have talked to say the steel piston works well, I opted to make mine out of graphite...self lubricating is the main advantage of that.

Bill

Offline wagnmkr

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Re: A "Poppin" Question
« Reply #4 on: January 05, 2014, 10:46:22 PM »
Thank You for all the quick replies. I haven't started this yet as I am gathering material.

It is good to know there can be a bit of variance from the plans, and still get a runner.

Cheers, and Thanks Again.

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline wagnmkr

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Re: A "Poppin" Question
« Reply #5 on: January 17, 2014, 01:07:50 PM »
Living in the Frozen North, I am having trouble finding a graphite rod supplier. None of my metal suppliers seem to carry it or know where I can get a small quantity. Does anyone know of some online suppliers?

Is there any reason why I couldn't use brass or bronze or mild steel for the piston? (Other than needing lubrication) I have lots of that in the required diameter.

Bill, when you bead blasted your frame, what size of a gun did you use, and what material? I have an airbrush compressor and was thinking along the lines of an Air Eraser type gadget as I have a LOT of machining marks to get rid of.

Cheers,

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline wagnmkr

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Re: A "Poppin" Question
« Reply #6 on: January 17, 2014, 02:49:00 PM »
In theory, I found some graphite rod online and it should be here next week.

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline b.lindsey

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Re: A "Poppin" Question
« Reply #7 on: January 17, 2014, 05:43:43 PM »
Tom, I used just a benchtop sized cabinet that I had here in my old office (similar to the picture below). I don't recall the size, but I used very fine glass beads, much much finer than typical sand. It won't remove heavy toolmarks or even all the light ones for that matter. You can use an assortment of other things to minimize them...sanding, dremel abrasives, polishing stones used in tool and die work, etc.  Once you get most of the tool marks out the bead blasting just brings it back to a nice even matte finish which I find appealing. I would think your air eraser would do the trick though it may take a bit longer. Remember to mask off any areas that you don't want affected (bearing fits, tapped holes, etc) and thoroughly wash the part once done. Those very fine glass beads have a way of hanging on even after blowing off with air.

Bill

Offline b.lindsey

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Re: A "Poppin" Question
« Reply #8 on: January 17, 2014, 06:23:31 PM »
Tom, I went and checked.  This is the grade of glass beads I used.  They are a 100-170 which represents the US Sieve sizes. Anyway the grainger link will give more details. Hopefully you can find a smaller quantity than 50 lbs. though :)

http://www.grainger.com/product/BALLOTINI-Glass-Bead-Blast-Media-2W766?s_pp=false

Bill

Offline wagnmkr

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Re: A "Poppin" Question
« Reply #9 on: January 17, 2014, 09:19:07 PM »
Thank You Bill.

I have found a supplier near me where I can get supplies from, including Grainger, so now I know the required size, I can pick some up. I am assuming that a coarser grit will just take off more material faster.

Thanks again.

Cheers,

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline b.lindsey

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Re: A "Poppin" Question
« Reply #10 on: January 17, 2014, 09:32:36 PM »
Yes as to being more aggressive, but will leave a rougher finish too and not to scale for an engine of Poppin's size.

Bill

Offline wagnmkr

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Re: A "Poppin" Question
« Reply #11 on: January 17, 2014, 10:40:54 PM »
Thanks Bill.  This is all new stuff to me and there is a bunch to absorb.

Who knows ... I may even get an engine built one day.

Cheers,

Tom
I was cut out to be rich ... but ... I was sown up all wrong!