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Member postings for Kettrinboy

Here is a list of all the postings Kettrinboy has made in our forums. Click on a thread name to jump to the thread.

Thread: Basic Clock Design
14/04/2016 08:28:04

Hi James

just a thought but looking at the drawing on your original post you say what have i forgotten , so where are the frame stays going to go , i would think that the frame plates need to be a lot wider to accomodate probably 4 stays , unless you are going to have just 1 at either end of a narrower plate , ive got a similar design of clock nearly drawn up but my plates are wider so the 4 stays at each corner of the plates clear the outside dia of the barrel and largest wheels.

Thread: Thread major diameter
18/03/2016 08:23:30

As said a full form insert as shown in the pic is the best way to get an accurate form , no need to set the compound rest over but just align one edge of the insert with say the chuck face and then cut until the thread outside dia is dead on and then from there its only a few thou to get to a 3A limit , at work we used thread parallels and ring gauges to check final size. but in the absence of these measuring the od of the thread works well.enough.

regards Geoffsnaptap.jpg

Thread: Colchester 2500-too big for first serious lathe?
09/03/2016 15:49:17

In my experience the Colchester 2500 Master is an excellent lathe , we had two at work and in the 15 yrs i was there they did 40-70 hrs a week year in year out and i dont remember anything going wrong bar the odd drive belt needing replacement and the clutch adjusting now and then , if i had a decent size workshop i,d have one of these or a Triumph 2000 in a heartbeat as theres virtually nothing you cant do on these lathes if they have all the accessories with them

regards Geoff.

Thread: Materials suitable for coolant.
02/03/2016 16:54:15

A bad point about using coolant with cast iron is if the coolant hasnt got sufficient oil content in it and the wet swarf is left sitting on the bedways of the machine the whole lot can turn to rust and potentially ruin a machine if its left more than a few days , the machine shops ive worked in always machined it dry and i do the same in my own workshop.

regards Geoff

Thread: Stirling Engine : Laura
28/02/2016 19:13:27

Hi Brian ,

whether oil is used on the power piston and cylinder depends on what materials are being used and how much clearance there is between piston and cylinder, on my similar engine which has an aluminium piston running at two thou clearance in a bronze cylinder i use contect duck oil as if I run it dry the piston would soon pick up after a few mins at high speed but using oil does cause a bit of drag on the cyl/piston slowing it down a bit , hard anodising the piston would perhaps allow it to run dry though , on all my other engines which use cast iron pistons in bronze or cast iron cylinders i run them dry as the graphite content in the cast iron seems to be enough to keep them from picking up and even after a 20 min run theres no marking on piston or cylinder , but you need a fine running clearance for them to seal and putting any oil in at all would slow the engines considerably , a cast iron piston in a cast iron cylinder is probably the ideal material selection for a cylinder and piston but a lot of other combinations also work well.

regards Geoff

Edited By Kettrinboy on 28/02/2016 19:15:07

26/02/2016 08:02:52

Well done Brian , i knew this engine could run and no doubt you will have learnt a lot about what it takes to get a running hot air engine so the next one should be no problem.

regards Geoffsmiley

25/02/2016 17:36:37

Hi Brian

John means Beta type engines where the power and displacer piston run in the same cylinder with the displacer rod running in a bush through the power piston so they are sometimes called concentric engines i have built one and the compression is so high its hard to turn over yet with a flick of the flywheel it starts easily and runs fast ,  your engine is a Gamma configuration where the two cylinders are separate and connected by a pipe or passage , anyway i think when you get the displacer rod and bush fit sorted theres a good chance your engine will run.

regards Geoff

Edited By Kettrinboy on 25/02/2016 17:39:59

Thread: Slip Gauges
24/02/2016 08:31:16

Definitely on my list of things to get , Chronos have a set for 100 quid , we had inspectoin grade blocks at work to set micrometers and check components but for home workshop use these Chronos ones would be fine , just a shame they havnt got a metric set.

regards Geoff

Thread: Colchester student oil
23/02/2016 08:38:00

Hi Alex , there is usually a plate somewhere on the back on machines to say what oils to use , but ii can tell you that in our shop at work where we had 4 Colchesters two Triumph 2000 and two Master 2500 lathes the boss always used Shell Tellus 68 oil in the headstocks and none of them ever gave trouble in the 15 yrs i was there , a lot of makes do similar spec oils like for example the Esso Nuto series , ARC Eurotrade sell Rock Oil 32 and 68 machine oils but only in 1 litre bottles i think ,  i am going to get some 68 myself  to put in my Harrison L5 headstock , my boss usually got the 25 litre oil cans from Cromwell Tools as he had a trade account with them.

regards Geoff

Edited By Kettrinboy on 23/02/2016 08:40:18

Thread: Stirling Engine : Laura
21/02/2016 09:02:00

Hi Brian

When the engine is assembled in a ready to run state as you turn the engine over you should feel some compression or bounciness this shows that the work cylinder piston is sealing and that there are no bad leaks elsewhere in the engine , with the displacer cylinder or work cylinder removed then spinning the engine over and getting 14 revs would be good as it suggests no problems with friction in the linkages, on my similar engine when it is all assembled it will spin only one revolution because of the compression that should be there , with the displacer cap off it will do about 4-5 revs with a good spin of the flywheels , I still think the displacer rod fit on your engine is too slack and could be the one thing stopping the engine running and getting this right will help this engine to run , on a short displacer bush of say10 mm length you need to aim for around 0.02mm of clearance between rod and bush to keep a good enough seal and free sliding of the rod., you mentioned your flywheel elsewhere , I think this engine running properly can spin this flywheel but it may take some time to get up to whatever its top speed turns out to be ,theres nothing to stop you experimenting with lighter aluminium flywheels if the engine seems to struggle with the current one but I,d try getting the engine running with the one you have first as it does look good doesnt it.

regards Geoff

20/02/2016 09:09:23

Hi Brian , you say the displacer rod is 2.93mm dia and a 3mm h7 reamer will cut around 3.02 mm if your lucky so that would give a near 0.1 mm clearance between rod and bush , ive found 0.02-0.03 mm is the optimum clearance to get a seal and allow free movement of the rod , and thats in a 30mm long bush , i think yours is around 10mm long is it so you may be getting too much leakage at that point a piece of 3mm silver steel rod should be 2.99-3.00mm so perhaps remaking the displacer rod from that would bring the clearance back to something that should be good enough to work, really hope you get this thing running sounds like your close but if certain things are not right these engines just wont go., i would try a paper gasket between the brass frames as one blob of sealant squidging out will block the passage and you guessed it the motor will not run. lets hope these new bearings are an improvement

regards Geoff




Edited By Kettrinboy on 20/02/2016 09:18:22

13/02/2016 09:15:42

linkage.jpgThe displacer piston drive linkage on that engine looks over complicated and would need pretty accurate machining for it to run freely , any linkage on a hot air engine needs a bit of play to account for tolerance buildups elsewhere and the design on this one doesnt seem to allow much if any hence the tight spots , if you cant get this one running freely i would be tempted to convert to a single rod running a clevis at the cylinder end for adjustment of the displacer piston , see pic of my similar type engine , it doest look fancy but its far easier to make and it works very well.

regards Geoff

Thread: Harrison Lathe cross Slide. unfriendly index dial markings
30/01/2016 08:40:36

My 63 L5 is metric and has a radius reading crosslide dial , ive had it 30 yrs but if i had the choice i would have preferred a dia reading dial as it makes things a bit simpler i suppose at some point i could make a dia dial , i have made my own tailstock dial and though the thread in that is imperial but its still great for drilling to exact depthsharrison l5 tailstock dial.jpg

30/01/2016 08:40:30

My 63 L5 is metric and has a radius reading crosslide dial , ive had it 30 yrs but if i had the choice i would have preferred a dia reading dial as it makes things a bit simpler i suppose at some point i could make a dia dial , i have made my own tailstock dial and though the thread in that is imperial but its still great for drilling to exact depthsharrison l5 tailstock dial.jpg

Thread: Show Us Your First Steps
29/01/2016 08:55:05

Just dug out my first proper project out of the loft , i know i made it before i left school up my grandads workshop so circa 1978 then , what a brilliant grandad he was to let a 15 yrfirst engine.jpg old have free access to his machines and materials , soon after i got a job as a precision engineer and it put me off modelling for about 25 yrs , the engine is a twin cyl single acting oscillator , pretty sure it still runs though.

Thread: Harrison L2 lathe
25/01/2016 09:31:23

This site would be good place to start **LINK** i think you can order manuals for most machines here.

regards Geoff

Thread: Boring Bars.
25/01/2016 09:23:02

I agree for some jobs like bigger bores on awkward materials a toolblock would be more rigid than a bar held in a QCTP but for most model size machining the resulting  surface finish on a bore is more to do with the material , angles and tip radius of the cutting edge than it is with how the boring bars clamped at the toolpost . for my solid carbide bars with shanks from 3 to 10 mm dia i use bits of of 1/2-3/4 square steel bar bored out a good fit on the shank and a couple of grub screws to hold them in place , made them after snapping a small bar in half when i put it in a vee block.

regards Geoff

Edited By Kettrinboy on 25/01/2016 09:23:33

Thread: Parting off query
14/01/2016 08:44:17

Oa tougher materials like alloy steels and titanium when I get towards the breaking off point rather than risk chipping the tool or the part falling off i use a hacksaw to do the last 2-3 mm because indexable parting inserts are not cheap.

Thread: Stirling Engine : Laura
14/01/2016 08:29:32

Hi Brian

a 24 mm AF spanner will be the right fit on the nut , nuts and bolts are generally 0.1-0.2mm undersize across the flats.

Thread: Harrison L5a lathe
11/01/2016 22:50:36

Ah ok , you could try perhaps someone on there could help

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