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Part built Allchin 1.5 inch

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derek blake05/05/2019 12:53:27
463 forum posts
120 photos

a27ce534-0111-49b5-996e-657ceeeeeded.jpeg

Jeff Dayman05/05/2019 14:30:51
1621 forum posts
40 photos

The assemblies are looking great Derek! Progress!

Your gear guards look extremely neat - they are a hard thing to make.

Paul Kemp05/05/2019 16:51:54
308 forum posts
11 photos

Hi Derek,

Good to see you are still cracking on. Notice no one answered your question re graphite yarn. On big stuff you would normally cut seperate rings of packing and chamfer the ends together at 45 degrees to the axis of the spindle. However that is not really practical on small glands and valves so yes, wind your yarn around the spindle to a big enough 'lump' to fill the stuffing box and squash it in with the follower. Don't do it too tight, you will bend the follower! A gentle nip is good enough cold, then nip up when hot if it weeps. Generally a packing gland is never 100% leak tight, a small weep allows oil entrained in the steam to get to the packing.

Paul.

derek blake05/05/2019 17:39:52
463 forum posts
120 photos

Thank you Jeff, I could take all the glory but I did decide to get gear guards laser cut but they were still work to build up.

thanks for the question answer Paul, I was supposed to make all my glands to except O rings but for some reason I forgot.

this would have got rid of having to use yarn but I will now have to make the best of it.

regards

Derek

derek blake30/05/2019 10:48:46
463 forum posts
120 photos

Hi All

Some updated pictures of progress, I have a small question please.

I have fitted the gears in the compensating centre, the spur gears are held on by 1/4 silver steel pins, however I had to ream the gears to get them to rotate but its left ever such a small amount of rock on the gear not the pin, do you think this will be ok? thanks in advance

engine 2.jpgengine 1.jpg

 

Edited By derek blake on 30/05/2019 10:49:21

derek blake30/05/2019 11:48:40
463 forum posts
120 photos

Sorry I meant the small bevel gears, 3 off

Paul Kemp30/05/2019 23:14:41
308 forum posts
11 photos

Derek,

"small amount" of play will be fine. In practice the diff gears only really rotate when turning corners and then only a tooth or two at a time or depending on the set up if winching where they may turn proper. If you look at any full size engine gears, your small amount would translate to a brand new running fit! If you think about the age of these machines many of them are well past their sell by date in terms of gear wear but they still run just find albeit a little on the noisy side!

Paul.

derek blake30/05/2019 23:24:23
463 forum posts
120 photos

Thank you Paul, I’m actually having difficulties with the diff at the moment.

when it’s all assembled on the axial and wheel fitted its locked up, I’m guessing the gears are too tight so I’m going to try some shims to push the gears apart slightly hopefully this will free it up as it’s awful at the moment and won’t rotate.

Paul Kemp31/05/2019 00:15:09
308 forum posts
11 photos

Derek,

Afraid I don't know the detail of the Alchin diff as have never built one but when making the diff on my LS I left the centre boss of the diff housing (both sides) over length from the figure quoted on the drawing. I then set it up in the lathe first one way and then the other and gently faced it back to get a nice engagement with a bit of clearance / backlash on both crown wheels to the pinions. Worth mentioning all gears in the diff on my 6" LS are cast gears (as many full size engines were) so they are not as precise as machined gears!

As I am guessing on the Alchin I would say you are on the right track with shims. Ideally you want a little bit of backlash in the diff for smooth running.

Paul.

derek blake31/05/2019 08:30:06
463 forum posts
120 photos

Thanks Paul, its good to know I'm on the right track with the shims.

Regards,

Del

derek blake05/07/2019 15:19:18
463 forum posts
120 photos

Good afternoon

ive been working on the engine and am wanting to plum up the injector, I have one that’s to drawing but is missing a lot of the internal parts, if I wanted to use a off the shelve injector like someone has used in the below picture what number do I need, I see they they are sold as No 2,3 etc.

thank you in advance.

derek blake05/07/2019 15:20:27
463 forum posts
120 photos

8e03861d-04c5-40cc-952b-6150733744cd.jpeg

Paul Kemp05/07/2019 21:27:08
308 forum posts
11 photos

Hi Derek,

Good to see you are still pushing ahead. Traditionally model injectors seem to be rated in fl oz per minute. So in choosing a suitable one look at the volume of water in your boiler at running level and compare to the volume delivered per minute of any proposed injector.

General comment I would make is a lot of models seem to have injectors that are over capacity and will raise the level in the glass from empty to full in short order, some within a minute! While that may be desirable for some it is not very kind to the boiler as a large quantity of cool water squirted in by the injector knocks the pressure back which puts quite a significant temperature / pressure stress cycle on the boiler. It is kinder and more efficient to have an injector with a lower delivery that can be left on for longer if needed but if used regularly for smaller amounts you can control the pressure water level much better and do not have such wild fluctuations.

Others may well have different opinions but I have never come across a full size boiler yet that you can take from the bottom to the top of the glass in a minute or two! Generally the injectors are matched to balance or slightly exceed the water consumption at full load. Often on railway loco's you have two injectors, one having a higher delivery than the other to better match operating conditions.

Paul.

MichaelR06/07/2019 08:53:13
avatar
340 forum posts
57 photos
Posted by derek blake on 30/05/2019 23:24:23:

Thank you Paul, I’m actually having difficulties with the diff at the moment.

when it’s all assembled on the axial and wheel fitted its locked up, I’m guessing the gears are too tight so I’m going to try some shims to push the gears apart slightly hopefully this will free it up as it’s awful at the moment and won’t rotate.

Another thing, with a three pinion diff the spacing of the pinions have to be equal if there is any discrepancy the diff will lock, worth checking your spacings.

Mike.

derek blake06/07/2019 22:02:07
463 forum posts
120 photos

Thanks very much Paul and Mike.

i brought some shims to space the gears and I feel they rotate much smoother so I’m happy I think, injector I need to research how much water the Allchin holds and go from there.

i will update some new pictures soon.

derek blake14/08/2019 10:36:43
463 forum posts
120 photos

So its been a while but a good bit of news this week, my boiler is finished and will arrive next week.

this means I can fill that gap, and see how the engine will look.

As everyone will know I'm a complete novice in building engines and as such before I'm to fix the cylinder I'd very much like to ask a question.

I do have to read the book for setting out the cylinder, however when fitting it do you make sure that the piston has an equal gap each end of the cylinder bore on forward and back stroke.

I was thinking that I leave the end cover off and watch to how far the piston slides so that the cylinder is set the right distance along the boiler.

Regards,

Derek

Clive Brown 114/08/2019 11:11:42
266 forum posts
7 photos

Your thinking is correct. The piston screws along the piston rod for adjustment of the end gaps, with a locking nut to fix its position.

IIRC, Hughes shows the design for a 'C' spanner to use for this.

Edited By Clive Brown 1 on 14/08/2019 11:11:55

derek blake14/08/2019 11:15:19
463 forum posts
120 photos

Right OK, thanks Clive.

JasonB14/08/2019 11:40:33
avatar
Moderator
16272 forum posts
1722 photos
1 articles

Just bear in mind that under steam the boiler will elongate a bit but the piston rod and motion won't so cold settings of piston and valve will need tweaking when hot.

derek blake14/08/2019 11:43:31
463 forum posts
120 photos

Right I see, thanks Jason.

hopefully I can get the cylinder in the ballpark from the drawings and be able to tweak with the adjustments on the rod etc as mentioned.

I'm sure it will be fine, I just don't want to fit the cylinder in the wrong place and ruin the boiler but I think that's unlikely as I have an idea what's supposed to happen.

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