Trouble getting started

This topic has 64 replies, 23 voices, and was last updated 12 July 2013 at 11:14 by Anonymous.

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1 July 2013 at 22:09 #123594
Anonymous
Posted by RICHARD GREEN 2 on 29/06/2013 09:47:14:

Andrew, It boils down to this, "you build yours how you like, and I'll build mine how I like"

I completely agree; I don't suppose either of us are going to change our ways.

I'm not working on full sized engines; so far all the parts I have made fit together properly without the need for 'fitting'. Of course that may well change as I move onto the cylinder and motion gear assembly, where it is fitted to the boiler.

I agree that the computer will not help in setting the valve gear. But what it will do is help me analyse the existing valve gear and determine whether it works properly or not. And if not, the computer will aid me in designing my own valve gear.

Remember that I'm building two identical engines. So while there are no real mass produced parts, there are not insignificant numbers of things like spokes and strakes, plus the time consuming parts like the bevel gears. Of course there are also innumerable studs, nuts and washers to make.

When I've finished my engine I'll also be able to watch it and think that I built it, but also that I modified and re-designed some of it, and that I understand the mathematics behind the design.

Regards,

Andrew
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1 July 2013 at 22:13 #123595
Anonymous
Paul,

Personally I just plunge in with the parting tool and keep going, rather than try and widen the groove. Seems to work fine for me, like this:

I also part off under power feed, although that is more controversial.

Regards,

Andrew
1 July 2013 at 22:20 #123597
Paul Harrison 5
Participant
@paulharrison5
Ooooh that looks scary and the work piece looks microns away from the tool post!

I haven't parted off yet but I'm going to have to give it a go… fingers crossed
1 July 2013 at 23:04 #123606
Anonymous
It's not quite as scary as it looks. The toolpost is a fair distance from the work, it's an optical illusion of the picture. I wasn't completely parting off either. It may not be clear from the picture, but the wheel hub has already been drilled and bored, and is mounted on a home made split mandrel. Since I didn't want to damage the mandrel I left a wall thickness of about a 1/16". The hub is 3-1/2" in diameter, and the mandrel is 1-1/8", so the depth of the slot is about 1-1/8".

Regards,

Andrew
8 July 2013 at 17:06 #124116
Paul Harrison 5
Participant
@paulharrison5
Andrew, there are some beautiful radiused corners there. I take it that the work on both sides of the parting tool is for use?

How did you achieve those really nice corners?

Paul.
8 July 2013 at 17:56 #124120
JasonB
Moderator
@jasonb
You can do it a few different ways –

-use a radius/ball cutter though probably take longer to set up than do.

– grind up some form tools, like this guy did

– or just use a file on the corner of the work as it revolves which is what I did ( not on the lobes though )

J

Edited By JasonB on 08/07/2013 18:17:31
8 July 2013 at 20:31 #124135
Anonymous
Paul: The internal radii were formed with a 5mm diameter carbide button insert. The external radii were 'chamfered' by eye with the same tool and then finally shaped using files.

The work to the right of the parting tool is the front wheel hub outer cover. Once removed the end of the work to the left is cleaned up and the inner cover is machined and then also parted off, leaving the hub to be cleaned up to length.

Regards,

Andrew

PS: Look in your PM inbox
8 July 2013 at 22:16 #124145
Nobby
Participant
@nobby
For a male radius say 1/4" the width accros the 45degree chamfer mulitiply .250" x .828" = .207 "
then file so there are 2 at approx 22.5 Degrees all 3 same .or .375 x .828 =.310" try it it works
Nobby
8 July 2013 at 22:38 #124146
Nobby
Participant
@nobby
Hi Guys
Its old hat I know Nobby
8 July 2013 at 23:18 #124147
Paul Harrison 5
Participant
@paulharrison5
Thank you Andrew, Jason and Nobby. Nothing wrong with 'old hat' Nobby; I say that at the risk of restarting the CAD or No CAD debate!

Jason, FABULOUS photgraphs, really interesting and a real inspiration. I had been looking at making a ball turning device, BUT it requires milling… back to square one. Although I've emailed Warco to let me know when the mill is back in stock.

Andrew, 2 questions. First. what exactly is a button insert; I'm presuming it's a rounded equivalent to the triangular ones I have? Secondly, in your 'avatar' what are you sitting in?

Finally, sorry to everyone who's P.Md me, but I've only just checked it, still getting use to this forum malarky, but thanks for all your input.
10 July 2013 at 09:52 #124199
Anonymous
Paul: First, here's a picture of my button insert tool:

Second, I'm sitting in a Pawnee D, ex-crop sprayer, with an O-540 engine, flat six, 235hp and a 4 blade prop.

Regards,

Andrew
10 July 2013 at 18:30 #124236
Paul Harrison 5
Participant
@paulharrison5
Tht's a great tool, Andrew. I take it you choose the radius you want and then just let it cut?

I've also looked up the Pawnee and was surprised to find that it is an agricutural aeroplane. I expect that with trucks, traction engines, trailers etc, but not a plane!

Off for my second visit to the local model engineering club tonight.
11 July 2013 at 11:35 #124288
Anonymous
Paul: I'm not sure I quite understand your comment on choosing the radius? Using the tool directly you get the radius set by the insert, 3mm. I was wrong in an earlier post, the button insert is 6mm diameter. However, the tool is very useful for generating curves of larger radius, if it can be guided by other means. I have a hydraulic copy unit on my lathe, so the tool can be used to generate tapers and curves from a simple flat pattern, like these connecting rods:

The Pawnee is known as the 'aerial tractor', which is about right. Simple construction and controls, no attempt at streamlining and drag reduction and lots of protection for the pilot, as crashes are not uncommon when crop spraying.

Regards,

Andrew
11 July 2013 at 17:42 #124331
Paul Harrison 5
Participant
@paulharrison5
What I meant, Andrew was that you would choose a tool with a different size 'button' to suit the desired radius. Once set up you would then presumably use either the cross slide or top slide in a straight cutting motion to produce the corresponding curve?

Sorry, but here's another question… what is a hydraulic copy unit?

Paul.
12 July 2013 at 11:14 #124399
Anonymous
Paul: Thanks for the clarification. The round inserts do come in several sizes, but sadly each one requires it's own tool holder. They're not intended to be interchangeable on the same holder. The 6mm insert is the smallest; for larger inserts you need a fairly rigid machine to avoid chatter as the length of cut can be large. For most of my work on the traction engines the radii are not critical, so I just use the 6mm insert. If I need a definite radius then I'll grind up a HSS special or make one from gauge plate. You are correct that a straight cutting motion is used to generate the radius appropriate to the insert.

A hydraulic copy unit is a device that normally sits on the back of the lathe cross slide. The unit has a stylus that follows a master pattern, and drives the tool via a hydraulic cylinder to follow the same path. Thus a copy of the master is produced. They were commonly used in industry up until the 1970/80s, when they were largely superceded by CNC. Here's a picture of the unit mounted on my lathe, and in action:

The hydraulic copy unit is the lump in the top right. Not shown is the oil tank and pump. If you PM me an email address I can send you an article that explains hydraulic copy units and their use in more detail.

Regards,

Andrew

Edited By Andrew Johnston on 12/07/2013 11:15:22
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