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[ooyah/2]

Hi Mick,
That's O.K. just a use of different words, I have always used taper pins where you need to drill the shaft and ream the hole to put in the pin.

Having built several Stuart D10's and10V's all with Stevenson reverse gear a taper pin thro' the sheave and the shaft is a bad idea.
.
DEREK
Some time ago you told me that you don't build engines which is O.K. so let me explain how you adjust the timing with Stevenson reverse gear.
You need to be able to move the sheave around the shaft to get the proper timing and once it's set if you put a taper pin through thro' sheave and the shaft it's there for ever, so if by some mishap or some thing else you need to re-time the engine you are snookered.
Now what Mick calls a taper pin is actually a grub screw ( you must forgive him , he's only a wood butcher but a darned good engine builder ) and the use of the grub screw allows you to re-set the timing if required.

 I am sorry I can't  can't figure out what you mean, you have lost me, you can't compare a toy steam engine to a gun but if I ever required info on a gun or weapons you would be  "MY MAN" to keep me right.
Derek, what is HPGS ?
I can only go by facts ,either by calculation or experience and my experience knows that taper pinning a sheave to the main shaft is a bad idea.

John, there is very little strain on the eccentrics as they are only  driving the valve which is held to the cylinder face by steam pressure, all that is required is a grub screw otherwise STUART would have designed something else.
George.  

[gondolier88]

Hi Derek,

In a situation where there is plenty of 'meat' available between the two things located using a taper pin (full size engines, ordnance etc), small adjustments; ie. <10 thou, you can ream the taper out and put a larger and/or longer taper pin in.

In a model 10 thou is an awful lot of metal, as George says, at this size a taper pin is the last word, if you do it wrong you'd have to fill the taper in the shaft with braze and re-drill and taper ream it- not what you want when all you want is to rotate the sheave by .5 deg. 

Mick,

Looking great, as always!. Thats some very nice work on the eccentrics. If I'm keeping up (would make a nice change) your next pic's should be of an assembled engine...?

Greg

[Patternmaker]

Hi Greg,
Yes the next photos will be the assembled engine, doing a lot of jobs in the garden at the moment in this glorious weather, 24c for the last 7 days.

Any progress on your D10

Mick

[ooyah/2]

 You can't ream a hole out bigger and move the object by .010" as you are reaming on the same center line so no gain has been made.
If you move the said object by .010" and clamp it you now have a hole that is out of line, top and bottom and the drill will break as you try to bore out the hole which then if successful you would need a very large taper pin to make a good fit on the now large hole which will be seriously larger.
If the hole has offset edges not only will the drill break but the reamer will snag and break also.
To get some adjustment you would have to redrill a hole at 90deg and ream it out for a new  pin, this is very bad practice in engineering as you would drill thro' the old hole.
If an item is to be taper pinned to a shaft the design will call for that item never to be moved.

If you take this to the launch engine which has a 5/16" main shaft it will be seriously weakened, this is why the design doesn't call for taper pins but grub screws to allow for adjustment.
George.

[gondolier88]

Hi Greg,
Yes the next photos will be the assembled engine, doing a lot of jobs in the garden at the moment in this glorious weather, 24c for the last 7 days.

Any progress on your D10

Mick

  That would require spare time! Seriously, busy with my 1:1 scale dinghy at the moment, and like yourself spring brings all those wonderful pleasures such as gardening/painting etc- at least the sun is shining- though up north it's only been 12 deg.C.

I await your next installment with anticipation.

Greg

[derekwarner]

Guys....an alternate view on a few fundamentals in basic minature engineering

A 3.0 mm HPGS [commonly termed as a hollow pointed grub screw] according to UNBRAKO is available in a number of forms....a] knurled hollow point, b] flat face, c] hollow pointed inverse cone, d] dogs point

Any attempt to alter a previously set position with a [knurled hollow point], [hollow pointed inverse cone] or [dogs point] HPGS results on the need to redrill through the existing tapping......[naturally this action also has the clear potential to partially strip the previously established tapping    to remove the previously established seating surface ....

An alternative to this is dissamble the components....remove the previously established in-acurate mating surface>>>>>> reassemble & start again

Typically here, a 3.0mm  ISO metric tapping has a 2.0mm tapping drill size...and all you are attempting is to respot   the revised timed location on the component

Conversley my experience with #6 or #7 British Standard [HT] low dimensional tolerance [0.0005"] taper pins will enable radial adjustments in components in "minutes if not seconds" to be achieved

No holes are redrilled, simply hand re-reamed & the new timed location secured   ....Derek

[ooyah/2]

Derek,
I think we are talking about different things here, we started out here by Mick describing a grub screw as a taper pin which he clarified.
There is no need for a taper pin to be used on the sheave of the Stevenson reverse gear as the grub screw allows the rotation of the sheave for timing adjustment.
Mick prefers the pointed grub but I only use hollow point grubs.
If a taper pin was used it would be thro' the sheave collar and right thro' the shaft and taper reamed making adjustment impossible.

In the pic of a recently built D10 with Stevenson reverse gear you can see the grub screw in the sheave which when loosened, the sheave can be rotated for timing adjustment.



This pic is further advanced and you can see the grub screw on the sheave just behind the worm gear.



Here is pic of a 1/4"dia grub and a 2" taper pin.    With a 6 ba  grub screw tapped into the sheave all that is required is the grub to be loosened and the timing adjusted, I used to be able to purchase 1/8" long x 6 ba grubs but the only small size I can get now is 3/16" long.

If a taper pin is used it is impossible to alter the adjustment of a collar or any other item slid onto a shaft other than rotating the item to the setting require bore a new hole at say 45%   and re-reaming the hole, bearing in mind that to keep the object in the same position you will drill into the old hole.

So are we on the same wavelength?, after 42 years in the engineering industry  would you please describe how to say adjust a collar on a shaft by re-reaming the hole.
So not sure if we are talking about the same thing but would like to hear how it's done.
Thanks for taking the time to answer.
George.

[derekwarner]

George......I don't want to get too far off track here  ....but....

1. a few years back I had an issue with the Stevensen reversing gear on my JMC3H horizontal engine
2. the M2 hollow pointed grub screws were not capable of being tightened or removed   ...& hence the reversing gear would not function
3. the answer was that the M1.1 AF in-hex of the M2 HPGS had cracked across the hex points
4. the only solution was a new weigh shaft + reversing arms...at great expense as the manufacturer accepted no responsibility for an engine that had never been commissioned
5. in addition to the new arms I installed M2 SHCS [socket head caps screws] which were capable of being tightened

So from that day on I have had a love/hate reluctance to use small HPGS...........    Derek

[ooyah/2]

Hi Derek,
Very nice little engine and I now see 1- off the things that you posted about.
I like Socket head cap screws and socket grubs and use them in preference to Hex Heads when possible.
It's not a problem as you say that if you strip a tapped hole it's easy to go the next size up.

The other thing is about Taper pins and must stress that you can't move say the operating lever on the weigh shaft if it has been taper pinned to another position say  .015" and then re- ream the hole it can't be done.
A new hole must be bored with the lever in the new position and then re-reamed.
Thank's for the pics
George.

[Patternmaker]

My pennies worth on grub screws, I personally do not like HPGS, from past experience with these on converted petrol engines and other hardware associated with the running gear for model sports boats, that is why I use 45 deg tapered point grub screws.

Once the timing has been correctly set there should no need to alter the position of the eccentrics, with screws that I use the point marks the position on the crankshaft which can then be drilled at 45 deg to the depth of the taper which does not weaken the shaft, and will never move.

Thats my opinion but then what do I know I'm only a wood butcher!

[Patternmaker]

Anyone contemplating building a Stuart Twin Launch engine check your cylinder casting exhaust port diamensions, I had a problem with mine, one port is 3/32” off centre top to bottom resulting in the slide valve not covering the exhaust port at BDC so it would be open to steam. I have had to make a larger slide Valve to compensate, and adjust the steam chest casting to accommodate it.

I contacted Stuarts about the problem in fairness they did offer to send me a new cylinder casting and slide valves which I declined because of the amount of work to machine a new cylinder and match all the other components.

[Patternmaker]

Engine assembled, next job engine bed plate, boiler pump, oil separator, condenser, boiler and launch to fit it all
in.

[ooyah/2]

Super job Mick, it would put a lot of professional engineers to shame.
When you see such a well made engine it only makes us try harder to compete and raise our standards.
George.

[Patternmaker]

Thanks for your generous comment George.

Mick

[Patternmaker]

Macc Model engineering supplies unique way of cutting copper pipe, they do add a little extra length, but what a waste you loose 1/2” of each end so 12 customers equals 12” of waste, 100 customers 10ft, why not use Tube cutter, as they sell them.

[oLiV]

hum... a way to do it faster I guess...

Anyway, very good job, Mick ! I'm working on mine too at the time. I have 2 questions for you :

- why did you machine most parts of the Reverse links from brass instead of steel ?
- could you tell us where did you find the worm gear you have set up on the crankshaft end ?

Thanks a lot !

[Patternmaker]

Oliver, the gears can be obtained from www.hpcgears.com
The reasons I used brass for the reverse links, appearance and less parts to rust.

How far have you got with your engine and how about posting some photos.

Mick

[oLiV]

Thank you for the link Mick, will be helpful 

Here are some pictures of my engine. As you can see I decided to modify somewhat the Stuart drawings for the cylinders and steam chests studdings.

[Patternmaker]

Looking good Oliver, why did you decide to change the studs on the valve chest to the same as the Stuart Compound engine.
If you are going to fit a worm gear on the crankshaft for a boiler pump you need a minimum of 4cm of shaft from the end of the bearing cap with double eccentrics.

Mick

[Patternmaker]

Engine base plate & boiler pump, the pump crankshaft has 4 options for plunger stroke length.

[Patternmaker]

Suggestions required please from steam experts, I want to make a condenser that will fit on the engine
Bed plate, the maximum dia that will fit is 2” if I make 5” high this will give me a volume of 1.032 litres will
this be sufficient for this engine?

Mick

[Aeronut4]

I'm no expert  but I'd have thought that around 0.5 litre would have been more than sufficient, if you're talking about an oil separator rather than a true condenser. It looks like you've got cylinder drain cocks fitted, so there should be very little carry over of water after the engine is warmed up and they are closed.

[Patternmaker]

It's a Condenser Oil Trap

[ooyah/2]

Mick,
I have an oil trap on my CERVIA which is powered by a D10, this is 35mmDia x 60mm long and is mounted above the water level on the funnel.
It drains thro' a 5/32" pipe overboard and this is sufficient for this engine.
I don't have drain valves on the engine so to get rid of the condensate I turn the prop over by hand until it clears.
I have fitted a by pass valve to the exhaust before the oil trap which allows any contaminated water to be fed overboard into a can for disposal, that's it painted red on the pic, when the engine is running clean I switch the valve over to send the exhaust up the funnel.

You will find that a slide valve engine only needs the needle valve on the displacement lubricator to be opened just a crack and when running the water drains from my trap " clean ".
Oscillating engines use much more oil than a slide valve as they are inclined to "gulp ", they do, but nobody so far has told me why, possibly because they use straight thro' lubricators without an adjusting needle.

One of the disadvantages of the drain valves is that they allow the condensate to flood the boat and with the quality of your work I am sure that this will not be acceptable to you.

You have made a super job of the launch engine, not bad for a" wood butcher" I will send you some BRASSO for your birthday.

George.

[Patternmaker]

Thank you George for your information, very helpfull.
I use T cut, I find it better than Brasso.

Mick