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Member postings for Andy_G

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

Thread: Chinese lathe
25/02/2021 17:32:39
Posted by Julian Newstead on 25/02/2021 14:17:22:

Hi I am new to machine work have bought a 7x12 lathe CD 210V and need help, I am trying to find out what the original gear set up is for the power feed . Got in a bit of a muddle with the gears.🤔

There are photos of a 'CD 210V' change gear setup on various ebay listings (whether it is the *same* CD-210V or not, I don't know:

Listing is here if the picture doesn't work:

https://www.ebay.co.uk/itm/UK-CD-210V-MINI-Lathe-Machine-Tool-Woodworking-Table-Metal-Gear-750W-Spindle-CE-/154105712191

Thread: thresher belts
21/02/2021 14:23:50
Posted by Paul Lousick on 21/02/2021 12:34:21:

40ft sounds about right. A steam traction engine would be about 20ft away from the threshing m/c and the belt would be made from a number of lengths of leather, each laced together.

 

Not sure if it's a date thing, or a location thing, but all the belts hung up in the back of the barn on my grandfather's farm in West Wales were canvas. (There were about half a dozen: about 8" wide and rolled up into a coil about 3' across.) These would have last seen use in the 1940s or 1950s - my mum was born in the 1940s and remembers the threshing machine coming to the farm.

In the 1970s he still used flat belts to drive a feed mill and a terrifying circular saw from the tractor. These belts were also canvas with metal 'claw' joiners. The belts were dressed on the inside face with what looked like an oversized lipstick - the outer case was about the size of a 'Smarties' tubs and made of orange cardboard.

Edited By Andy_G on 21/02/2021 14:25:39

21/02/2021 10:48:59

I came across somebody making them from book-binding tape a while ago - seems to give a reasonable scale appearance (even better in a tan colour IMHO):

Thread: Rumely Oil Pull engine
17/02/2021 17:03:56
Posted by not done it yet on 17/02/2021 16:59:15:
One, that I was thinking of, was about 117mm piston diameter and 5.2 litres capacity.🙂. Even if the valves/piston rings leaked slightly, they would still start quite easily.

Yeah, I suspected something as such.

I was seeking to address the "may not be appropriate to a small scale model" concern

17/02/2021 15:37:30
Posted by not done it yet on 17/02/2021 14:36:02:

The compression ratio for some engines of that era were not high. I have come across engines with a CR ratio of 4.1:1.

That may not be appropriate to a small scale model, mind.

My little horizontal engine is designed with 4:1 compression ratio, and runs quite happily with noticeable compression/bounce when flipped over (~21mm bore).

Leaky valves seem a likely suspect.

Thread: Warco Lathe Query
16/02/2021 19:50:44
Posted by Squint on 16/02/2021 17:53:30:

What's the question if the answer is cock robin?

Does it start: "Batman....?"

Thread: Could I try an IC engine?
16/02/2021 14:27:40

That’s the way I would propose to do it. It’s the way I made my one and only single cylinder IC engine crank shaft. (Steel crank webs silver soldered to silver steel shaft & crank pin).

I await more learned comments with interest.

15/02/2021 19:57:48
Posted by bernard towers on 15/02/2021 13:30:22:

Sorry not kept up with the thread but the Westbury jig is in ME 12th July 1962 pages 56/7, if you need copies I will scan and send plus a photo of my jig. Note this is for cam flanks.

Sorry - I thought you were referring to an engine design (My fault!). I'm guessing it is the same one as in the Seal construction article - Link and also the type used in the video above.

Thread: 3 HP Frisco Standard Stationary Single 4-Stroke IC Engine
15/02/2021 18:51:09

Posted by PatJ on 15/02/2021 15:43:40:

So I would guess that the commercial gears that have either the 45 degree angle, or the metric with the 21.5 degree angle will mesh if they are the same module/pitch, (both must be either 45 or 21.5 degrees of course), and the same diameter gears will produce a 1:1 shaft speed ratio.

Yes, two 45 degree helical gears of the same hand will mesh at 90 degrees with crossed axes. However, 45 degrees is something of a special case as both gears in the pair have the same helix angle. Otherwise, the helix angles just need to sum to 90degrees - think of a worm wheel as a single tooth helical gear with a >85 degree helix angle.

I'm guessing that the 21.5 degree helical gears are intended to mesh on parallel axes (as per spur gears) in left and right handed pairs. If one wished to create a 90 degree drive with these, the matching gear would need to have a helix angle of 68.5 degrees (90-21.5 if I've done my maths correctly).

I suspect that the reason that only 45 degree skew gears / crossed helical gears are readily available is that the number of other variants would be huge otherwise.

From the above, it sounds like you are more comfortable with DP than module. I'm the opposite, but will try an example:

Pitch diameter of a spur gear is [#teeth]/[DP]

=> 60 tooth 40DP spur gear has 1.5" PCD

Pitch diameter of a helical gear is [#teeth]/([DP] x [Cos(b)]) where b is the helix angle.

=> 60 tooth 40DP 30 degree helical gear has 1.732" PCD

=> 30 tooth 40DP 60 degree helical gear has 1.5" PCD

Note that [DP] corresponds to the pitch *normal* to the tooth - i.e. on a plane rotated by angle (b) wrt the gear axis. The tooth outline looking down the axis of the gear will not be the same as a 40DP profile (although there is a way of specifying helical gears by this profile, the normal DP (or module) still needs to match for them to mesh).

If you play with the angles in the 30+60 degree example, you can see that the centre to centre spacing of the pair (sum of PCD/2) can be varied while keeping the same gear ratio and normal DP.

The contact between the gear teeth is largely sliding so they aren't ideal for transmitting high loads.

I hope I haven't further confused you!

14/02/2021 23:11:11
Posted by PatJ on 14/02/2021 18:10:05:

1. Will two helical gears mesh and operate properly at 90 degrees if the angle is not 26.6 and 63.4, as long as the sum of both angles equals 90 (yes/no) ?

Yes.

The 'magic' helix angles give two gears that will mesh at 90 degrees with the same PCD, but one being twice the number of teeth than the other (2:1 gear ratio).

If both are 45 degree helix angle, for example, the larger gear will be twice the diameter of the smaller for a 2:1 ratio.

Gear ratio is all about the number of teeth, nothing else.

Gear diameter (for a given module / DP) is determined by no. of teeth *and* helix angle.

For skew helical gears to mesh, they must have the same *normal* module.

Thread: Tufnol, Phenolic, SRBP, HPL, CGL, SGL
14/02/2021 14:03:55

Lab worktops are often made of ‘Trespa’ - a trade name for some type of laminate. It’s horrendously expensive, but you may be able to buy an off cut. (It cuts & machines OK with TCT woodworking tools.)

Thread: Could I try an IC engine?
14/02/2021 10:22:56
Posted by Danny M2Z on 14/02/2021 05:53:33:
The cams in a 4-stroke engine take a bit of a beating, as do the cam followers and the rockers so unless it's a display engine (demo runs only) then consider case hardening and grinding the relevant parts if you want it to last more than an hour.

* Danny*

Is that still the case with something as slow revving as the Seagull? (Asking, not arguing! )

FWIW, the Seagull's cams are machined as pairs and 'loctited' onto the camshaft.

13/02/2021 22:43:47
Posted by Paul Horth on 13/02/2021 21:40:49:

I was considering the Westbury Seagull two cylinder engine, available as a kit of castings from Hemingway.

Charles Lamont sets himself an impressively high bar!

I've also looked in depth at the Seagull and like you, discovered it is not at all straightforward due to the number of errors in the drawings and the marginal nature of the castings.(See also https://modelengineeringwebsite.com/Seagull_revisited.html ).

However,

As far as I know, there is no requirement to harden and grind the cams for this type of engine (although one may wish to for authenticity).

The end of this video shows how cams can be machined on a lathe:

I'd be intrigued to find out more about the Westbury 'Jig' (I can't find anything by searching for it).
Failing that, I might cobble up my own twin cylinder.
11/02/2021 17:02:15
Posted by Paul Horth on 11/02/2021 16:37:24:

My specific question now is about the precision needed for angular location of the cams relative to each other and to the register which locates the shaft in the timing gear.

In truth, as long as one is not looking at a high performance ("racing" )  engine, they don't need to be very accurate to get a running engine - maybe 5 degrees, or so? You could probably get away with 10.

There's a way of cutting certain cam profiles fairly accurately on a lathe using a series of arcs which is straightforward, but a little tedious.

 

Edited By Andy_G on 11/02/2021 17:25:29

Thread: Recommendation for next project
08/02/2021 08:39:34

Lots of people have successfully built Websters (it seems to be something of a rite of passage).

Have a look at the Kerzel hit and miss engine - similar open crank design as the Farm Boy, but also built from bar stock. (It does need some milling, which is why I didn't build it).

Plans are very good, and freely available.

http://www.floridaame.org/GalleryPages/g1h0106.htm

(edit for correctness! )

Edited By Andy_G on 08/02/2021 08:52:55

Thread: Mini Lathe Vertical Mill Attachment
04/02/2021 23:26:56

This is mine, with the vice centred on the available cross slide travel - you can see that it's a fair way from the centre of the tool post (the hole between the two allen screws):

It's fixed using the compound slide mountings on one side, and a couple of tapped holes on the other. The mounting holes are arranged so that the plate can be removed without disturbing the slide. I added a dowel to the back side which, in conjunction with the spigot on the compound mount, ensures that the plate goes back in the same place each time without needing to be trammed in.

I'm sure a proper mill would be better if you have the money/space for one, but this has its uses.

Edited By Andy_G on 04/02/2021 23:29:07

Edited By Andy_G on 04/02/2021 23:32:02

04/02/2021 16:56:30
Posted by COLIN MARTIN 2 on 04/02/2021 16:23:51:

I contacted Warco and asked if it was suitable for the mini lathe, but received a useless answer, so I'm none the wiser.

If yours is a typical mini lathe, you may find that the centre of the tool post won't traverse much further than the axis of the spindle, so unless that Warco attachment was mounted offset from the toolpost (in the manner of a cutting tool), you would be limited to using half the width of the vice for milling ops.

Thread: Loctite made in China?
03/02/2021 19:33:57
Posted by Andrew Tinsley on 03/02/2021 17:40:48:

I got the Locttlf version. I didn't realise the spelling wasn't Loctite for a couple of days!

Andrew.

It's very cleverly done - even with the bottles side by side, it isn't obvious.

Where did you buy it from?

02/02/2021 16:56:01

Not the same stuff that Mr Crispin ended up with, is it?

Edited By Andy_G on 02/02/2021 16:58:35

Thread: 3 HP Frisco Standard Stationary Single 4-Stroke IC Engine
02/02/2021 09:56:27
Posted by PatJ on 02/02/2021 05:49:59:

Andy-

I showed my wife the Antikythera mechanism, and asked her some questions, such as "where did they get the metal to begin with, where did they get the tools such as hacksaws, files, drill bits, etc.,

off topic: If you explore the Clickspring channel, he makes the metal, drill bits, files, etc. using contemporary technology. It really is remarkable.

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