Recent Posts

Pages: [1] 2 3 ... 10
1
From Kits/Castings / Re: Textile Mill Diorama
« Last post by crueby on Today at 01:19:34 PM »
Hi John, great tip on the tables, thanks!
2
From Kits/Castings / Re: Textile Mill Diorama
« Last post by J.L. on Today at 01:16:40 PM »
I agree Bob. Creativity; the mother of invention.

Hi Chris,
I read on your steam shovel thread that weight was becoming an issue when moving the model around. I too, have had to have help in moving my diorama off the saw table so that I could use the saw. I have had good luck with stainless steel tables (18 gauge) with castors. They are not as secure or stable as what you are considering,but they certainly make life easier.

Wheels on the bottom of the cart can be a problem with vibration and movement, even with the wheels locked. In the second photo, I have shown stabilizers that can be dropped down with adjusters that take the weight off the wheels and make the table very stable. Much like heavy equipment drop jacks to lift the vehicle off the tires before they start to do thier work.

Cheers...John
3
Chatterbox / Re: Talking Thermodynamics
« Last post by MJM460 on Today at 11:49:44 AM »
Hi Willy, I completed those calculations this afternoon.  I have tried to attach a print of the section of the spreadsheet so you can see the basic steps in the calculation.  My cheap printer makes it quite difficult to get a good clear print from a spreadsheet.

Basically I calculated for a full disk for each of the rim sections, and also for the centre part which is missing.  Using negative density, or subtracting the centre is probably the easiest way to calculate the moment of inertia for the rim.

That flywheel has a moment of inertia of 945,000 x 10-9 kg.m2, approximately 3 times the moment of inertia of my 75 mm flywheel, largely due to the larger diameter.  You can see the spokes and hub make an insignificant contribution, while the majority comes from the outer rim.

The brass bar has 40% higher value, 1,337,871 x 10-9 kg.m2

A steel bar 150 mm long x 25 x 12 mm has a value roughly half of this, 663,000 x 10-9 kg.m2 which would make a convenient half size step up from the flywheel alone.  You can see this would make a very simple temporary flywheel to give you an idea of what you need.  The formula for a bar about its centre of gravity is I = 1/12 x m x R2.

The calculated mass was 567 g for the flywheel and 556 g for the bar, a little higher than the measured weights.  The error is probably density differences for the exact alloy your metal is made from, but also the mass is quite dependent on exact measurements.  I expect the discrepancy is within a reasonable tolerance, and more than satisfactory for the purpose.

But while I was doing the calculations, I could not help but wonder why the extra moment of inertia is required.  Your double acting engine goes through zero torque at the top and bottom dead centre, but for a free running engine it really does not take much of a flywheel to get it through that zero to the point where there is again plenty of torque to overcome friction.  I would expect your flywheel is more than adequate for running, and should even give good speed regulation, even under load.

How does the engine behave without the brass bar?  Does it stop at each dead centre, or just always stop at one end?

I am wondering if you have had the valve chest cover off and carefully checked the eccentric settings.  First I wondered if you just had early cut off which gives a bigger range of rotation at zero torque for starting, but once you spin it over by hand to get it started, there is air pressure on the cylinder during expansion after cut off so most of the range of zero torque disappears.  I don't think this is the issue.

However, if the admission is early, probably depending on the exhaust closure point as well, you could get full steam pressure in the cylinder before top dead centre, which would require much more moment of inertia to turn past the top dead centre and keep it running.  If steam reaches full pressure before top dead centre, the flywheel has to supply enough energy to push some of that steam back against boiler pressure until the piston reaches the top dead centre.  Similarly at the bottom dead centre.

I hesitate to tell you how to set the valve gear, and diagnosis is difficult from such a distance, especially with no information on what was happening that you needed the extra flywheel.  The only obvious thing I can think of is early admission so the steam reaches full pressure before the piston reaches top dead centre, but I am confident that you will be able to find the issue.

In any case, I would not suggest modifying that nice looking flywheel yet.

I hope that is helpful,

MJM460
4
From Kits/Castings / Re: A V8 maybe
« Last post by Jo on Today at 08:44:00 AM »
Hi Pete, I noticed that your previous photos have been hit by the Photosuckit scam  :disappointed: so I trotted off to Photosuckit to remind me of your build only to find that other than the home page I can't even click on the individual pictures on there and get to see them  :rant:

Good luck with getting it running  :)

Jo
5
From Kits/Castings / Re: A V8 maybe
« Last post by metalmad on Today at 03:28:18 AM »
Thanks guys Its good to see you all again
Pete
6
Vehicles & Models / Re: Chris's Marion 91 Steam Shovel
« Last post by Steamer5 on Today at 03:18:13 AM »
Hi Chris,
 Mines the 226 kg version, an earlier one with out the hand brake, mine has brakes on the wheels

https://www.machineryhouse.co.nz/Lifter-Trolleys

I have the popcorn delivered by the truck load! Have a silo with auger to deliver to the house, re-stock on a monthly basis up until a couple of months back now its every 2 weeks!!  :ROFL:

Cheers Kerrin

PS just checked & its not a hand brake but the release to lower the table, mine has a peddle next to the pump peddle
7
Vehicles & Models / Re: Chris's Marion 91 Steam Shovel
« Last post by crueby on Today at 02:58:32 AM »
Hi Chris,
 Can recommend the hydraulic trolley. When my slaves err minions err kids left home I got one to move the trains & trolleys around, makes life easy & safe!

Cheers Kerrin
Which brand did you get?


Can use one to move the sacks of popcorn in to use when reading all the threads here!
8
Vehicles & Models / Re: Chris's Marion 91 Steam Shovel
« Last post by Steamer5 on Today at 02:44:52 AM »
Hi Chris,
 Can recommend the hydraulic trolley. When my slaves err minions err kids left home I got one to move the trains & trolleys around, makes life easy & safe!

Cheers Kerrin
9
Vehicles & Models / Re: Chris's Marion 91 Steam Shovel
« Last post by crueby on Today at 02:34:19 AM »
The tough part is going to be lifting it, may need a cart, not sure how heavy it will be, but its already over 20 pounds.   :thinking:

I'm available to help.  :naughty:

But if I were you, I wouldn't trust me just as if you were me, I wouldn't trust me.

Wait...that doesn't sound right.  :thinking:


 :insane:


Um, and you were a software engineer...   :ShakeHead:


At least you couldnt run fast carrying the shovel!


Seriously, well, a bit, well, not much... The Shay is a foot or so shorter than this model will be, I can lift it and carry it a short way, but its easier with two people. This model will be longer and taller, plus probably twice the wieght. May get one of those carts that jack up and down.
10
Vehicles & Models / Re: Chris's Marion 91 Steam Shovel
« Last post by zeeprogrammer on Today at 02:26:57 AM »
The tough part is going to be lifting it, may need a cart, not sure how heavy it will be, but its already over 20 pounds.   :thinking:

I'm available to help.  :naughty:

But if I were you, I wouldn't trust me just as if you were me, I wouldn't trust me.

Wait...that doesn't sound right.  :thinking:
Pages: [1] 2 3 ... 10