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Member postings for DrDave

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

Thread: Compound Beam Engine
03/08/2022 18:44:28

Thanks for the link, Jason. I was not aware of that web site. Seems the compound beam engine was more common than I thought!

03/08/2022 17:52:55

Down in Taunton last week, we found this beam engine in the museum. It had been used to power a local silk mill.

I have not seen a twin cylinder, compound beam engine before. The high pressure cylinder has both a smaller diameter and stroke, compared with the low pressure cylinder. If I didn't have 20 other projects on the go, it looks like a good subject for a model.

Compound Beam Engine.jpg

Thread: What Did you do Today 2022
29/04/2022 18:52:03

What didn’t I do today? Turn anything! I pressed the “go” button on the remote for the lathe and nowt happened. Fortunately the supplier led me by the hand, via email, to reset the inverter. Some more troubleshooting pointed to the remote. Fortunately I have a spare, so swapped them over and all is well again.

Thread: Looking for a non-magnetic, strong, easily glued material
29/04/2022 18:47:06

At the risk of going back on topic…. Lasaero.com list both 2024-T3 and 7075-T6 in 0.040” thickness. 2024 is out of stock, but would not really suit: they only do Alclad, which has a thin coating of pure ally both sides, so it fails the scuffing requirement. They do have 4’ x 2’ sheets of 7075-T6 showing as in stock at £45, and they are based in the UK.

Thread: What Did you do Today 2022
27/03/2022 11:57:15

I dropped in on our local auction house yesterday. Out-bid on what I went for, but I came home with a lovely little oscillator steam engine instead. It would have cost more to buy the brass to make one, so quite chuffed (no pun intended) with it.

Thread: Emco F1 Mill Upgrade
03/03/2022 19:53:01

Hi Neil,

To be honest, I haven’t used my F1 for a while, so I am working from memory. I normally use 6 mm or 10 mm cutters, occasionally a 25 mm insert slot drill. I don’t feel the need for larger: just get your CAM software to program a suitable path (I use Fusion 360).

Feeds and DoC? In the higher strength aluminiums, I would think that full-width on a 6 mm HSS cutter, I would be conservative and have a depth of 0.5 - 1 mm. The machine has an ammeter for the motor current. I find that very useful to tell me how hard it is working. And when the cutter is getting blunt!

I have milled steel (up to En8, nothing fancy), but I forget the details. It seemed to take forever, so I might have been pussy-footing. 0.25 mm DoC, perhaps and trying not to use the full cutter width.

I hope that this helps

Dave

Thread: Songs about Engineering
23/02/2022 12:12:26

Pink Floyd’s “Welcome to the Machine”?

Thread: Lock nuts / Jam nuts - MEW 311
07/01/2022 17:21:43

Oops. My “steel buildings” was a bad choice…. I did the analysis of a couple of lifting frames last year. Bolted together with clearance holes. By reference to Shigley’s book, we have assumed that the holes yield until all the bolts are active at ultimate load. But we digress.

Duncan, I see your point. Tightening the top nut gives a preload on the lock nut, which in turn transmits part of this to the bolt shank. This suggests that you should only use lock nuts where the preload is unimportant.

07/01/2022 14:01:47

Why interesting, Michael? A modern steel building is held together by shear bolts, and the average aeroplane is peppered with them. I agree that applying shear through the threads is a no-no, but they bolt shank is fine.

07/01/2022 13:43:59

Ah! That's got the hornets going again... To address the earlier point (which appears to have been removed) if you put the thin nut on first, it will strip when you dissemble the joint. If you consider what happens, this is clearly not the case.

I.e. install the (thin) lock nut first and tighten to, say, 25% torque. This gives roughly 25% preload. Add the main nut & torque fully. This unloads the thin nut (and actually reverses the load that it sees, providing the locking function) and gives full preload to the assembly.

If the main nut is removed, it goes back to a thin nut applying the 25% preload: it cannot retain the full preload because that was introduced by the (now removed) full nut.

We do seem to have moved into two spheres here: the "technically correct" thin nut on first, and the "historically or aesthetically correct" thin nut last!

One point that might have been missed, asI found from the ESDU Data Sheet that I referenced, is that this all applies to bolts that are predominantly loaded in shear. For those in tension, a lock nut is not required (have you seen many on a car engine?).

And lastly, as others have pointed out, lock nuts are not an acceptable locking mechanism for safety critical applications anyhow. So is the order really that important?

Thread: The Workshop Progress thread 2022
05/01/2022 21:19:15

I've finally got the flywheel for my Corliss engine as one part, rather than a bag of bits. I seem to spend more time making tools to make tools to make things than actually getting bits made! Just need a couple of rattle cans from Halfords to finish it (after cleaning off the excess adhesive).

flywheel.jpg

Thread: Lock nuts / Jam nuts - MEW 311
05/01/2022 21:04:26

I have been following this thread (no pun intended) with interest because I was also in the thin nut on top frame of mind. Now that I am back at work after the Christmas break, I have been able to look up "lock nuts" in our technical libraries. The first reference that I found was in the ESDU (Engineering Sciences Data Unit) library, one of the go-to sources of data for Aerospace Stress Engineers. ESDU 14002 "Lock nuts and other thread locking devices" notes that "it is preferable to assemble the thinner nut first because the threads of the second nut are required to carry a greater load. However, this is not essential". In addition to this, the Data Sheet gives the theory behind this statement, showing the load transfer between the various parts of the bolt and the two nuts during the various stages of tightening.

OK, it still looks wrong to my eye, but the thin lock nut should go on first, as noted by the OP and the references that he has linked to.

Dave

Thread: Aircraft General Discussion
14/08/2021 21:13:29

A DH Rapide has been flying around south of Bedford most of the afternoon. I suspect that it has been visiting Old Warden, possibly to give pleasure flights.

dh rapide.jpeg

03/08/2021 09:55:13

There was an air show at Old Warden on Sunday afternoon. Possibly aircraft from there. There was (I think) a Spitfire holding north of the airfield mid-afternoon that you might have seen/heard.

08/07/2021 17:45:41

The first scheduled flight that I took was on a Dakota. Every time I see one flying, it makes me feel old…

Thread: Self-Lock threads
26/06/2021 09:01:40

An interesting concept. Thanks for highlighting it.

Thread: Aircraft General Discussion
06/06/2021 15:46:21
Posted by Andrew Johnston on 06/06/2021 15:41:05:
Posted by Mike Poole on 05/06/2021 22:08:32:

You might get another look tomorrow.

Yep, she flew over my mum's house in north Bedford about 2 hours ago, heading SW.

Andrew

And she’s just gone over us (south of Bedford) on her way home.

Dave

Thread: Tokamak is still on the go
11/05/2021 11:17:34

ITER is aiming for 150 million degrees. JET is probably similar (it is over 25 years since I worked there...). The point of ITER is to scale up the JET reactor to get closer to a power reactor, i.e. one that can run for months and produce significantly more power than it uses. I am not sure how making a smaller tokamak fits in with that progression.

Thread: Multico high speed drill info
28/04/2021 18:40:09
Posted by Michael Gilligan on 16/04/2021 10:02:57:

Dr. Dave had a similar enquiry **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=139922&p=11

... but apparently drew a blank with the links that I provided.

It looks a mighty useful machine [deep throat], so I hope you have more joy.

MichaelG.

Blimey, you have a good memory, Michael! I never did manage to find any info on my drill...

Dave

Thread: Have You considered getting a 3D printer
16/04/2021 19:59:12

Spurred on by this thread, and an Amazon voucher from my employer for Christmas, I finally bit the bullet & invested in a Sovol SV01 printer. It only took a matter of days for Mrs Dave to go from "and what are you going to use that for?" to "magic has entered the house!".

After printing a few tool and collet holders from Thingiverse, I tried a dial gauge holder: not only is it too big for my dial gauge, but it didn't fit the QC tool post either... So, out with the CAD, measure up a standard Myford tool holder and a few hours later, this appeared:

dial gauge holder.jpg

The gauge is a nice push fit and it fits the tool post as-is. It just needs the screw for height adjustment (I printer an M5 thread to see how effective this would be.

Chuffed with the result!

Dave

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