The Workshop Progress thread 2018

[Jon GibbsParticipant @jongibbs59756]

Posted by John Haine on 02/05/2018 22:52:13:

Why wouldn't a lathe one work? The geometry should be just the same whether the tool or the work rotates.

+1, I use several cheap Chinese SCLCR boring bars with CCMT-06XXX inserts shortened and turned down to 3/8" in my boring head very successfully.

The slight trailing droop of the insert makes no difference in practice and in fact seems to put the cutting tip right on the centre line of the boring head for me. For larger bars you can mill a flat on the bar wherever you like to get the tip to lie on axis if you're that concerned.

The banggood ones come with 10 inserts for around a tenner which is under the £15 import threshold if you can wait that long (2-3 weeks).

HTH

Jon

[MeunierParticipant @meunier]

Posted by John Haine on 02/05/2018 09:38:47:

Inspired by another thread, I got one of these 133 mm backplate castings from RDG…

My mind must have been wandering because I immediately jumped to the (wrong) conclusion and wondered how you were going to cut the 133 teeth on that…..hmmm
DaveD

[richardandtracyParticipant @richardandtracy]

Posted by Jon Gibbs on 03/05/2018 10:41:29:

Posted by John Haine on 02/05/2018 22:52:13:

Why wouldn't a lathe one work? The geometry should be just the same whether the tool or the work rotates.

+1, I use several cheap Chinese SCLCR boring bars with CCMT-06XXX inserts shortened and turned down to 3/8" in my boring head very successful…

The banggood ones come with 10 inserts for around a tenner which is under the £15 import threshold if you can wait that long (2-3 weeks).

HTH

Jon

Absolutely agree on this. If you start with the -S10 there's less to turn down and the holder's cheaper than the S12 too. Think I got my -S10 for under £4 last year, but without inserts (of which I already had enough) from cskwin2015 on E-Bay.

Regards,

Richard.

[john feeneyParticipant @johnfeeney58965]

Thank you John & Joe,

Thanks for the information. I`ll look into selecting a motor and a power supply. For my application I will often need to run for up to 30 mins so cooling may be a problem along with bearing life. Joe, in your set up how do you clamp the motors?, in all the small out runner motors ( IOO watts) I have used the outer case rotates along with the shaft. Perhaps I`m missing some thing simple !

John

[Craig Booth 1Participant @craigbooth1]

I worked on my bench, new top and task lighting, whiteboard for scribbling on, and tool stand for commonly used bits.

[Joseph Noci 1Participant @josephnoci1]

Posted by john feeney on 04/05/2018 09:49:44:

Thank you John & Joe,

Thanks for the information. I`ll look into selecting a motor and a power supply. For my application I will often need to run for up to 30 mins so cooling may be a problem along with bearing life. Joe, in your set up how do you clamp the motors?, in all the small out runner motors ( IOO watts) I have used the outer case rotates along with the shaft. Perhaps I`m missing some thing simple !

John

John, The motor has a face/flange that is normally fixed to the model plane's bulkhead/firewall, with the rotating motor body having the prop fixed to it at the non-flange end. The motor shaft normally protrudes from the rotating motor body at the end opposite to the mounting flange. That is not great, as the motor normally has a larger bearing at the flange end, and a smaller one at the 'prop' end we work like it opposite. What I do is remove the motor shaft altogether, and fit a long shaft ER series collet chuck, with the chuck at the flange end. Fix the flange to your machine mount, and all should be clear..

Some pics and explanations-

The motor below right is 60mm diameter, has a 10mm shaft. The prop mount is fixed to the rotating motor body. The opposite end where the shaft protrudes is the mounting flange end – butts up against the mounting surface and screw hold the flange against said surface.

The lower left and centre is a motor with the outer case and shaft pulled free of the windings – the left is a view of the motor mounting flange.

]

This is a smaller motor, again the left bottom view is the mounting flange end – the top view shows said flange at the left side.

And another motor – the one I use on my CNC router/engraver – Has 10mm shaft which I replaced with an ER collet. The flange is seen on the left

And the motor stripped: The mounting flange viewed end on at left view.

This is a view of the high speed sensitive drill I made – the aluminium body a bearing at the load end and the ER collet shaft goes through them, into the outer body of the motor ( replacing the original motor shaft) The motor mounting flange is seen screwed onto the aluminium body.

Heres a cross section, if it helps..

regards

Joe

[mechman48Participant @mechman48]

Stripped down my vertical cross engine; found that the location bosses top & bottom of cylinder covers were blocking the air/steam passages, the dwg says these should be 1.5 mm, had to machine back to 0.75mm to allow air to pass into cylinders… still not convinced this is enough tho'. need to double check spool valve clearances as well. Will look at making up another plate to combine both exhausts into one similar to Jim Nic's model…?

George.

[JasonBModerator @jasonb]

George you will find that if a small area of the spigot is milled away where the passage is you can get a good airflow and still keep the full spigot length.

.

[mechman48Participant @mechman48]

Thanks for the tip Jason; will do that next time in the man cave, still need to sort out the spool valve methinks.

George.

[John HaineParticipant @johnhaine32865]

Posted by John Haine on 02/05/2018 09:38:47:

Inspired by another thread, I got one of these 133 mm backplate castings from RDG…

…and created a lot of cast iron dust to liberate this:

Used in anger for the first time today. Seems much more rigid, better finish, pleased!

[Mark RandParticipant @markrand96270]

Quick change Gibraltar toolpost .

[mechman48Participant @mechman48]

Following Jason's tip I titivated both top & bottom cylinder covers, milling a small cutaway into the locating bosses. Having already machined back the bosses to 0.75mm. I didn't have much option but to leave it as is. It certainly improves the airflow to the cylinder but still have air passing the spool valve… definitely something wrong with spool valve, size, clearances, methinks making a new one is the solution… … need to clean up the covers

​George

[Jim NicParticipant @jimnic]

George

I'm a little puzzled by your having problems with the spool valve on your Vertical Cross engine as in my experience they are normally simple to make and reliable. I have a total of 5 such valves on 3 different engines, all have used 6mm silver steel rod as the basis for the valves working in a 6mm reamed bore.

These from my Paddleduck are the most complex:

Good luck with the investigation, I hope whatever cure is required is not too drastic.

Jim

[mechman48Participant @mechman48]

Thanks Jim.

​Could you possibly pm me the sizes of the spool piece on yours, ( if handy ) I've a sneaky suspicion that the dimensions on mine may be slightly out compared to the dwg, possibly the ID of the cyl bore & the OD for the spool valve have too much clearance. I have a couple of other models that have spool valves & like you said… no bother with them… just this one being an awkward sod… probably something stupid on my part… can't see the wood for the trees etc.

Geo.

[Jim NicParticipant @jimnic]

George

I've checked my retained drawings and have noted no "improvements" to Stew's design so all I can say without stripping the engine is that the valve is made to drawing.

The valve chest is almost to drawing, the only changes are making it with a closed bottom end (rather than boring it all through and then plugging it) and putting the exhaust holes on the front face to facilitate a cover with an exhaust pipe.

Where is the leaking air in your engine going? My valve may also leak but any air could only go down the exhaust pipe and I wouldn't know! (I'm now going to have to go and check, of course)

Jim

[mechman48Participant @mechman48]

Jim

​My Valve chest & spool valve are made as per dwg & the air is going through to exhaust ports, I suspect that the spool valve body is not closing over the inlet / exhaust ports completely, plus there may well be too much clearance in the bore / valve od as mentioned previously hence their must be something out on the dimensions on my model. I will 'Percy veer', thanks for your assistance so far.

This is dwg I have… so unless I'm missing something on this …?

George.

[Jim NicParticipant @jimnic]

George

That's the same drawing as I used. I checked my engine last evening and there is no appreciable leakage past the valve at its operating pressure of less than 10 pounds per squinch.

Just a couple of suggestions of possible causes for your problem could be: incorrect valve dimension, a less than good fit between valve and bore, or incorrect positioning/range of movement of the valve. Given that the valve is made to drawing how closely does it fit the bore? If that is satisfactory is the throw on the eccentric correct and is the valve rod the correct length and set to move the valve at the correct time in the crank cycle?

Jim

[mechman48Participant @mechman48]

Jim

​All things I need to recheck, your first two suggestions are the most likely I reckon. Ta!

Geo.

[JasonBModerator @jasonb]

I decided to do a bit on teh Otto Langen which has been sitting about waiting to have the 300mm long CI cylinder bored out to 42.8mm.

I posted a while back the bar being turned to fit the lathe so the next job was to machine the hole for the Microbore insert to fit into which went without issue.

With the boring bar made there was no excuse not to make the cradle to hold the column so a few bits of steel and aluminium were cobbled together and bored out to fit the column.

With the small spacing blocks removed the column could be gripped and the boring bar slipped into position.

Then a few long boring cuts in both sense of the word.

Not too bad a finish and no chatter which was good, will need a bit of honing and or lapping but that's easy enough. The wavy line is just where the vacuum cleaner nozzle rubbed.

[jimmy bParticipant @jimmyb]

Made some chuck keys for use in the drill, to make changing jaws a bit easier and quicker.

I was going to put flats on the drill chuck end, but figured that it'd just slip if there was any obstruction !

Jim

[mechman48Participant @mechman48]

Sun actually; Made a new spool valve, original was too short, + too much clearance 'tween the valve & bore. new valve seals off the ports better from what I can see & the valve is a neater fit in bore. Next noticeable fault… crank throw doesn't seem to be enough to allow full stroke of valve sequencing… methinks some numpty ( ) wasn't taking enough care on dimensions throughout build……

George.

[Jim NicParticipant @jimnic]

Look on the bright side George, at least you don't have to worry about what your next project is going to be yet.

Jim

[mechman48Participant @mechman48]

It works !… finally got my Vertical Cross to run, the stroke of the valve rod wasn't long enough to set the positioning of the spool valve correctly so I had to drill deeper into the valve coupling plus re-tap thread deeper, this gave me extra adjustment to position the spool valve correctly. I had sealed the valve chest gland with graphite thread & this also helped, I need to pack the cylinder gland as this is passing air, obviously this is not giving full air volume/flow to the cylinder. Still need to titivate, do a few more mods, clean up, degrease, prime, paint, make cylinder cladding etc. so it's another strip down so still plenty to do… but at least it works…

​George.

[JasonBModerator @jasonb]

Well don sir, you got there in the end.

[mechman48Participant @mechman48]

p.s. still need to do some alignment as there is some crankshaft float, as can be seen on video, although packing the cylinder gland will help centralise the piston rod as well as sealing the cylinder so …

​George

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