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Gowest

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gowest

1048 posts

Hi Westcountry

i like the name?

Rob's comments have put me on the spot but over the years I have built a few engine and in doing so found the things I like about the different types

First there are 3 engines built by Hornby they are the A4's and the 2 A3's the early one and the late one 

Buying second hand is always a problem and you might get a good engine or a bad engine how they have been used and if enough oil or after care has been carried out to keep them in good order as these engines like the full size engine need more care before and after a run.

So any of the range that Hornby made are ok and will be a good buy if the seller can tell you that it's condition is good with no faults.

the A4's are a straight live steam engine the only point to watch are does it have the vacuum pipe on the front buffer beam and coupling hook other things to Look for are the handbrake control in the tender and water scoop handle this will also apply to the A3's plus on A3's check the front steps are not broken off just behind the front buffer beam.

if possible take a look at the front wheel boggy set sub frame base if it has had very little use the paint on the under side will be in good order if the engine has been run loads of time the paint here will be scratch down to the cast meatal base.

i think the best of the range from an engineering point of view is the last of the A3's this engine has a good oil control system and can be listed as the only A3 with a removable chimney but really nothing to choose from the range they are are all good fun and give hours of fun never two runs are the same so it will be your choice at the end of the day that matters and if you need it Hornby and J H can sort out any problems you might have.

ken

gowest

1048 posts

From an engineering point of view BA threads a very similar to metric threads and any one in the larger world of model engineering use BA threads so as you say these started life 40 years ago I would think it more than likely that BA threads were used but maybe Rob can find out.

ken

gowest

1048 posts

Then in that case I do not know as I have not worked on aRocket but one of the engineers at Hornby must know try emailing them

ken

gowest

1048 posts

Hi going spare

i thought that as the question was live steam trains I thought he was referring to the A4's and A3's I'm not familiar with the Rocket?

ken

gowest

1048 posts

Hi colroy

the thread size for most of the very small screw is 1.2mm hope that helps

gowest

1048 posts

Hi Rob

will try it out on my servo unit and tell you how it worked out

The picture is of the finished servo test unit with a Hornby PCB under test, when testing my servo units I will have to connect them up to the green terminal block as I do not use the 2 pin plug idea.

gowest

1048 posts

As I was talking abouit a test unit for the servo unit which would help me fault find and improve my own design servo units I spent a little time giving it some thought and this is what i have come up with.

Hornby Servo Test Unit.

A test unit which can be used to check the Hornby servo PCB this make life a little easier for me when building my engines as it allows me to test the Hornby PCB or the ones that I have designed on the work bench rather than putting the engines together and powering up my track.

You could just use a simple switching circuit with relays only as in the drawing below with no electronics but as I will be using this test unit quite a bit I think I will build the unit using the 4011 gate IC.

How it Works.

Working in a similar way to the Hornby controller with a servo unit connected to the white plug and the test lead connected to the motor out terminal on the PCB, Switch 3 is operated in the ON position the volts to the Hornby PCB will be 16 volts.If SW1 is pressed both relays pull in RLA and RLB RLA will switch the volts from 16 volts to 9 volts this low voltage is needed to operate the small relay on the Hornby PCB.RLB is wired as a change over relay and will switch the output polarity to the white plug pos to neg.The indication for this operation will be shown by the LED’s 1 and 2 the green being Forward and the red Reverse. If SW2 is pressed then only RLA will operate again switching the volts from 16v to 9v this time RLB will not operate as the diode D1 will block the volts to this relay.

The Hornby servo board is pictured here and the 2 connection that supply the electric motor are the out side 2 sockets this is where the indicator LED’s LED1 and LED2 must be connected to. 

Here I put together the simple test unit and it is pictured below. I have connected it to a Hornby servo board which is under test with the power ON no LED’s have lit up which is good as this means the small black Hornby servo board relay has pulled in which is what it is supposed to do when 16 volts are on the track.If the relay driver transistor had failed or any of the other components including the relay then one of the LED’s would be ON. It can be that a bad connecting might be the fault then the next test will prove this as no LED’s will light when the push buttons are pressed.

To carry out a Test.When the green switch SW2 is pressed the volts drop from 16 volts to 9 volts.This drop in the voltage turns OFF the transistor driving the relay so the relay drops out.This action causes the relay NC contact to close and the green LED lights up.If you release the push switch SW2 the LED will go out. Each time the green switch is pressed the green LED will light.

Like wise when the blue switch SW1 is pressed the red LED lights up this means that the polarity has change and as the Hornby relay only has one set of contacts wired each time the polarity changes only the LED that is wired to work on the correct polarity will light up. In the engine this is indicated by the fact that the electric motor will rotate one way with one polarity and if the polarity is changed then the motor spins in the opposite direction.

 

The unit below works the same as the previous design the only difference is the switch operations of SW1 and SW2 are recorded by the 2 green LED’s LED1 and LED2.In both of the test unit cases the PP3 batteries will not be able to supply enough amps to be able to test the PCB in the engine as the heater takes 3 amps and the motor might present a problem to.A different supply with more power would have to be found to achieve this.

Now I have my test unit I can sit down and see why my servo board is failing to work properly.

 

gowest

1048 posts

If its not one thing its some thing else turns up just when you think you have found the problem and put the engine on the track bang something  you over looked pops up or didn’t account for.

I have thought keep putting the engine on and off the track is a pain why not a simple test unit? Will give it some thought.

Look closely at the picture here you might be able to spot the capacitor with a big black burn mark in the centre of it.This component should be a nice deep yellow colour all over with a orange line denoting the positive end and some writing saying 47uf 25v.

The reason for this capacitor burning out is due to the little black square component to the right which is a bridge rectifier and this had for some reason stopped working and just gone into a full short and stopped giving out a DC output so by sending the wrong polarity to the capacitor thereby making it go pop.

That’s all part of life I can remember back in the 1964 working for a small electronic company and my job then was testing TV repeater amplifiers they were then switching from valves to transistors and this unit I was testing had Mallard OC71 transistors like in the picture some of you may have come across them. The TV amp problem was a 50 cycle hum which I had spent a long time trying to find out why I decided to leave the unit powered up over night and go home as I switched off the room lighting I could see the scope and the fault went I switched on the light and the fault came back.

The picture here is of such a transistor and is coated in black paint this is because the transistors are made from a clear glass tube this paint had got damaged in the wiring shop and it was this that made the transistor now light sensitive and was picking up the mains 50 cycles from the room lights. The OC72 has a metal case, the red dot is the collector lead. To remember the 3 transistor leads we had a saying. From the red dot it was... Cross the British Empire or Collector, Base, Emitter a bit of history

Having said all that it still leaves me to find out why this servo board is not working I hope its not the SSR as its my last one and I will need to reorder some.

I thought I would add this as some might find it interesting, in the first picture of the tank engine in the section you can see my oiling pen this is great for electric and steam engines it has a very fine needle so you can get into some tight places it is filled with clock oil of about the right viscosity and just right for small moving parts  I find this oil ideal for live steam engines.

Years ago the Tri-ang company sold oil for there electric train which I can remember having a small bottle of just as the picture. it had a short brass wire fixed inside the cork to drip drops of oil onto moving parts 

The live steam engines have many oiling points and if you look at the under side of the Hornby engines there are 4 main oiling points which need frequent attention even full size engines had a good oil up before starting a run.

There are the 3 main driving axles and the gear bearing block.In the picture I’m oiling the rear set of drives and the very thin needle goes right through the plastic brake ssembly oiling hole and into the cavity of the axles and bearings.

And do not forget the tender wheel set axle boxes and the power pick ups these are most important the axle boxes can seize up which I have had and will wear a flats on the wheels and once corrected you end up with tap, tap, tap noise as the train runs round the track. The same problem has happened on full size electric rolling stock when the hand brake has been left on.

Well looks like I’m burning some night oil to see if I can get this PCB fixed as until this is done I can not take the next step which is to see if steam can be raised and a run under taken.

gowest

1048 posts

Well I thought by now I would have something to report but sorry to say no its the electronics that are proving a problem and not wanting to play ball.

gowest

1048 posts

Hi Rob

yes would be good oneway or the other to see this project completed as looking on the first page in the forum I started this engine a year ago 8th August 2019

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