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Author Topic: PM Research #7 first model  (Read 651 times)

Steam Technology

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Re: PM Research #7 first model
« Reply #15 on: September 05, 2020, 05:17:57 pm »
Excellent progress and +1 for taking it steadily. I sometimes have to stop myself from accelerating towards the finish and give myself time to ponder the project.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #16 on: September 06, 2020, 12:22:37 pm »
Learned something today. In hind sight it was a stupid mistake.
I’ve seen this method of aligning the cylinder to the four jaw but you have to have a perfect casting. I don’t.
I’m not sure what I’m going to do. It is a learning experience but it’s off center .040”. The unfinished bore is off .025”.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #17 on: September 06, 2020, 01:27:47 pm »
I don’t imagine I’m the first guy to bore off center on these irregular castings.
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Stoker

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Re: PM Research #7 first model
« Reply #18 on: September 06, 2020, 02:33:40 pm »
How's the runout on the other end? If I recall correctly, these cylinder castings are symmetrical, and so can be swapped end for end. I would align the best end of the cylinder on the frame and cap the most off center end on the dead end. You may also have enough room to go to a slightly bigger piston and cylinder bore, to bring it back to concentric alignment.

Four jaws are wonderful tools, but can easily get you in trouble. I usually try to just spot face first to provide a check for centering, and do a small bore through to check co-axial alignment, before approaching final dimensions.

Hindsight is wonderful, isn't it ......  but yes I do believe this sort of thing has been done before, a time or three!
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classixs

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Re: PM Research #7 first model
« Reply #19 on: September 06, 2020, 02:36:21 pm »
Very nice progress so far :)

That cylinderbore offers a good reason to upgrade to a slightly bigger bore/piston (if there´s room ofc)...
Learned something and more power to the engine when finished...win-win ;)
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Nu2modlin

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Re: PM Research #7 first model
« Reply #20 on: September 06, 2020, 04:03:05 pm »
Stoker,
The bore is consistent from end to end. I measure .238" and .239" on the narrow side of my mistake.
I've had the wind cut out of my sail. I need to walk away for today.
Meanwhile, I replaced the bearings in an electric motor I'm overhauling for my son's table saw.
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Stoker

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Re: PM Research #7 first model
« Reply #21 on: September 06, 2020, 06:03:05 pm »
Quote from: Nu2modlin on September 06, 2020, 04:03:05 pm
Stoker,
The bore is consistent from end to end. I measure .238" and .239" on the narrow side of my mistake.
I've had the wind cut out of my sail. I need to walk away for today.
Meanwhile, I replaced the bearings in an electric motor I'm overhauling for my son's table saw.

You do have another option to consider here Jeff, and it is the one I'd likely give the most consideration too, were it me.

PM Research does sell individual parts for their kits, so there is that option for you to think on.

Meanwhile .... walking away can be a very good thing sometimes ...... but you'll be back, I've no doubt what-so-ever!!!
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Steam Technology

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Re: PM Research #7 first model
« Reply #22 on: September 06, 2020, 06:51:21 pm »
That's a buggar.
A new blank casting is probably best.
It can be tough on morale but learning something means the day has not been a total waste.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #23 on: September 06, 2020, 09:46:34 pm »
I really don’t have a choice.
I sent an email to pm research.
I won’t be happy with anything else.
Every time I looked at this model I would say, you should have replaced it and done it right.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #24 on: September 07, 2020, 09:42:29 am »
Question for you guys,
How do I center the cylinder in the chuck?
If it wasn't bored it would be easier.
I've been thinking about this. What I have come up with so far is, I place it like before using the mandrel. I then remove the mandrel so it's just outside the rough bore. I measure the three sides of the cylinder to the outside of the mandrel to even out the distance.
Is that clear as mud?
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Stoker

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Re: PM Research #7 first model
« Reply #25 on: September 07, 2020, 11:10:38 am »
One way to go is to either use a mandrel, like a gauge pin or just some round stock, that has the same diameter as the cylinder and indicate off of that, with your fourth jaw out of the way. If you don't have such a properly dimensioned piece of bar stock laying around you could just index off the inner or outer jaw faces themselves.

Clamp the cylinder in three jaws of your four jaw chuck, centered by eye to the best of your ability, with the cylinder set deep in the jaws so you can get the tip of an indicator onto the lip of the jaws. Move the jaws as needed to bring all indicated readings to the same number. Back one of the opposing jaws off the very least that you can and still move the cylinder, then bring the cylinder back up to the front of the chuck jaws where you want to work on it, then screw that slightly loosened jaw back in just the amount needed to clamp back up and then bring the fourth jaw in to clamp onto the steam chest bulge. You should be good to go at that point.

Hope that helps settle the mud out a little bit.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #26 on: September 08, 2020, 03:47:53 pm »
I ordered the cylinder today. The total including shipping was less than $20.
I would say that's well worth it for my piece of mind. The next time I machine a cylinder it will come out much better.
I hope  ;)
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Steam Technology

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Re: PM Research #7 first model
« Reply #27 on: September 08, 2020, 04:45:13 pm »
Quote from: Nu2modlin on September 08, 2020, 03:47:53 pm
I ordered the cylinder today. The total including shipping was less than $20.
I would say that's well worth it for my piece of mind. The next time I machine a cylinder it will come out much better.
I hope  ;)

Not worth messing about at that price. ;)
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Nu2modlin

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Re: PM Research #7 first model
« Reply #28 on: September 09, 2020, 11:44:20 am »
Stoker,
I have been reading your method, it seems like a viable way to go.
The mandrel idea was my first choice but now that I think it through, I really need to measure off the outer rim of the cylinder. Your method of indicating the three jaws is reading off the three point cylinder circumference.
I like it.
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Nu2modlin

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Re: PM Research #7 first model
« Reply #29 on: September 11, 2020, 08:25:10 pm »
I received my new cylinder today from PM Research.
Wow, that is good customer service.
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