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Member postings for tractionengine42

Here is a list of all the postings tractionengine42 has made in our forums. Click on a thread name to jump to the thread.

Thread: think tank
27/01/2012 11:53:41
I am in agreement with Coalburner and Ady1.
 
Improving the forum search facility should be high priority, information is only useful if it can be found.
 
Nigel
Thread: Magnetic bronze
27/01/2012 11:44:13
Hi
Copper alloys that contain iron, nickel, manganese or cobalt may be attracted to a magnet.

Could be Nickel Aluminium Bronze as suggested by Andrew or maybe a Copper Nickel alloy which often have some iron content.
 
Both should be OK to machine the Nickel Aluminium Bronze being the harder and tougher material
 
Nigel

Edited By tractionengine42 on 27/01/2012 11:45:02

Thread: setting up new Axminister ZX30
25/01/2012 13:52:00
I use Superlube grease and spray which I find very good. It's available from
RS Components and others,
 
I agree with Martin, the copper based greases are meant for bolting, they provide controlled lubrication when tightening and assistance when breaking out bolted joints that have been in service some time.
 
Nigel
 
 
Thread: Milling a semicircular groove, ball ended cutter, or?
23/01/2012 13:14:43
Sorry
Repeated post by accident

Edited By tractionengine42 on 23/01/2012 13:15:56

23/01/2012 13:14:41
Hi
Cutting the thread last in this material may not be a good idea.
I had a job where 2 semi-circular threaded parts had to be opened out to a larger internal thread size.
 
When mounted in a fixture in the lathe I had two oposite gaps 4mm wide, the material was En24T and 1-1/4" 8UN thread.
 
The tip of the threaded insert chipped very quickly, I cut the thread to size, turned or replaced the insert to present a new cutting point, backed the tool off and took a few very light cuts to clean up the thread profile.
 
20 thread tips to do 60 sets.
 
Probably not such a problem in softer materials but in En24T my experiance indicates you wil go through a few inserts.
 
Regarding using ball nose cutters, I mentioned this because I thought you were a woodruf type due to concerns abut stress concentration. Although slower I thought it might be more economical on cutting tools.
 
I wonder why you need a locking pin, My MGB has those konck on/off wire wheel arrangements, the nut face is tapered and engages a corresponding taper in the wheel. Once knocked on with a soft hammer its tight. never come slackened off yet, From memory I think the tapers have a slightly spherical profile
 
I was once shown a wheel nut off a formula one racing car, unbelievably thin in section and extraemly light, this was the same locking arrangement, the nut having a male taper engaging a wheel female taper of what looked like 45 deg.
 
Nigel
 

Edited By tractionengine42 on 23/01/2012 13:20:52

Edited By tractionengine42 on 23/01/2012 13:23:32

Thread: Girder crown stays - are they overstressed?
21/01/2012 20:06:17
Hi
Micheal William's interest in the Prince of Wales Fire box Girder Stays propted me to do some FEA on his behalf.
 
The results are as shown below. More results are shown in my album.
 
As can be seen the above is without girder stays.


and the above with girder stays.
 
These results show reduced stresses provided by the girder stays.
 
The analysis is done at a working pressure of 90 psi, material copper.
 
Even without the girder stays the design is quite robust IMHO, that's not to suggest they should be omitted.
 
I hope these results are helpful to those designing and building boilers.
 
Enjoy
 
Nigel
 
Thread: Milling a semicircular groove, ball ended cutter, or?
20/01/2012 15:40:27
Hi Ian
If the nut is Aluminium and the bolt a much stronger En24 how much load/stress is the bolt going to see that would cause consern for the bolt?
 
I would consider using a carbide round nose endmill, the carbide will give a good cutter life. The end of the groove will have a spherical radius therefore no sharp corners. I would not think this approach will give concern regarding stress concentration. The thread root will be much more of a stress raiser.
 
Not knowing application I hope this helps
 
Nigel
 
 

Edited By tractionengine42 on 20/01/2012 15:56:22

Thread: Snifting valve
20/01/2012 15:22:23
Hi Dave
I had been wondering about the workings of the snifter valve, now I understand.
 
Thanks for you help.
 
Nigel
18/01/2012 16:30:54
Hi David, Thanks for that info.
 
My Allchins TE that I am building does not have a snifter valve so a couple more questions come to mind.
 
1. Is a snifter valve used when cylinders have either piston valves or slide valves, or only when piston valves are used. (I am thinking a slide valve can lift to clear a vaccum)?
 
2. Is the snifter valve only applied when superheating is used for the express purpose of using the vaccum created to cool and protect the super heaters, so if super heaters are not used a snifter valve is not used? (Then any vaccum would be used to brake the engine).
 
Cheers
 
Nigel
18/01/2012 12:32:02
Hi
May I ask how is it that a vacuum is created. From what I can gather when the regulator is shut off a vacuum can be created between the regulator valve and cylinders. Are the pistons, now not being fed with steam, pulling a vacuum?
 
Thanks
Nigel

Edited By tractionengine42 on 18/01/2012 12:32:45

Thread: What is EN24 like to machine?
14/01/2012 11:59:25
Hi Raymond
Other than in the annealed condition En24T is the easiest to machine in the range T to Z.
All the conditions T to Z are hardened, they are given different tempers to achive different mechanical properties, T condition has the highest temper and therefore the easiest in this range to machine
 
I have not heard of En 24 M,
 
I have used En8M which is great to machine but is a lower strength material.
 
Nigel
14/01/2012 00:37:56
Ian
 
For En 24 the added suffix indicates the material heat treated condition.
 
En24 'T' condition is hardened and tempered and quite tough to machine, in my experience it's a case of reduced speed, small depth of cut and adequate feedrate when using a light machine. Carbide tools are best, you can go to high speed very fine cuts and feeds for finishing however I find good finish is relatively easy to obtain at slower speeds and plenty cutting oil.
 
In 'T' condition Its tensile strength and hardness are in the range of grade 8.8 to 10.9 high tensile bolts. Most high tensile bolts will be either one of these grades, socket head cap screws are generaly of a higher 12.9 grade.
 
If you have been machining high tensile bolts then EN24T wil be similar.
 
En24 is commonly available in annealled conditon (M???) and heat treated 'T' condition.
 
As John S indicates, 'M' condition is easier to machine than high tensile grade 8.8/10.9 bolts.
 
Nigel

Edited By tractionengine42 on 14/01/2012 00:43:32

Thread: To CNC or not to CNC - that is the question.
13/01/2012 11:03:48
Hi John
I am only scratching the surface with what I am doing, there is lots of free and very cheap stuff.
For 2D I use Draftsight and Vectric 2D, John S gave details above.
 
For 3d like the valve body I currently have the luxury of autodesk inventor which is very expensive. However, there are many other options that I am sure others can advise on one being Alibre for 199 pounds. I have used this and its OK. This will allow you to create your 3D model which you save as an stl file format. Vectric do do a 3d post processor but I use Meshcam for which I paid around 90 pounds.
 
You create your model in 3d software (Alibre), save as stl and load this into the post processor (Meshcam) which gives you the g code which you then load into your cam software (I use mach3 from Artsoft) The valve body was about 30 minutes form starting the 3d model to loading gcode into mach3.
 
The 3D modelling software does have a bit of a learning curve but online tutorials are great. If you can dedicate some time you will crack it in a coupole of days. The post processors Vectric and meshcam are dead easy, by short learning curve.
 
There are many more options.
 
FYI
I am only using a small shirline mill I bought for 200 pounds on ebay. Adding the controller and stepper motors cost about another 300 pounds.
 
I am not using ball screws, on the Shirline you can adjust backlash to below 0.1mm which I find Ok even when down milling, it does leave a witness mark when the feed changes direction but as I do the final finishing by hand it no problem. (You can see the witness mark on the inside valve body as the Z axis has changed from down to up) I don't use milling cutters bigger than 6mm, mostly 4mm and smaller.
 
Nigel

Edited By tractionengine42 on 13/01/2012 11:07:08

13/01/2012 01:12:32
Just to concur with John S comment about learning G code.
 
Reference to my post above, each part was programmed in 5 to 10 minutes without any knowledege of G code. The post processors used were Vectric 2D and Meshcam. 30 minutes is enough to learn how to use these programmes and start producing G code for real parts.
 
Getting started was not without problems, this and other forums provided fantastic support.
 
 
Nigel
12/01/2012 18:45:53
Hi
I recently added a small cnc facility to my workshop, while I prefer conventional methods which are much more interesting and challenging the CNC adds some options for parts that I can't do other wise.
In this respect I limit my CNC to a) Parts that need engraving/etching b) parts that would otherwise be expensive or long delivey castings c) parts that would require alot of fabrication and silversoldering. Here are a few examples.
 
 
Above is a water lifter in 2 halves to be silver soldered together and finished by conventional machining and by hand. Left is one half finished on the inside only, on the right the matching half complete inside and out.
 

Above is a steam header just off the cnc and ready for conventional turning/drilling and finishing. This would otherwise be a casting or fabrication.
 

Above are brackets ready for hand finishing. Could be done by conventional machining but I think most modellers would prefer a casting.
 

Above is a name plate ready for finishing and infill painting. This would otherwise probably be a casting or maybe etched.
 
For me the cnc adds some conveinience and control over buying castings. While I can fabricate I don't like fabrication involving alot of parts, my preferance here would be to cnc what I can.
 
Nigel
PS sorry for any bad spelling, I wish this forum had a spell check.
 
Thread: 20/40 DP gear hob
24/12/2011 06:05:41
Spoke to soon
I found the answer here
 
It's not an involute gear hob but it is an involute spline hob. The spline is 20DP but has a shallow depth equivalent to 40DP.
 
So no good for cutting gears I presume.
 
Nigel.
24/12/2011 04:53:41
Hi
I was looking at gear hobs on ebay.
 
This one is described as 20/40 DP,
 
I know what 20 DP is and what 40DP is.
 
How can it be both 20/40 DP? Can anyone explain this description?
 
Cheers
 
Nigel
Thread: Girder crown stays - are they overstressed?
23/12/2011 13:43:15
I have read with interest Jason’s and Michael’s comments above, both making valid points.

I quick look at the Princes of Wales boiler does show some interesting differences.
 
While I agree that the P of W girder stays look more substantial there arrangement/connection to the fire box crown has differences that will change the loading condition and stress distribution. Another observation is the Prince of Wales boiler appears to have a flat fire box crown (albeit thicker) whereas the D& NY has a curved fire box crown.

There is no question about the integrity of the design but I think it’s interesting to learn more about these girder stay designs. Michael, if you could give me more boiler details I would be interested in doing some analysis. If you send me a PM I will give you my email address.

How much does cutouts in the girder stays help water circulation? How much do they improve steaming?
 
Nigel
Thread: Bearing Material
21/12/2011 00:50:13
Hi Alan
Cast Iron bearings with mild steel shafts is a very traditional combination, the graphite in cast iron helps provide lower friction. Cast Iron is also good when used with hardened steel shafts.
Cast iron will tend to 'glaze over' considerably reducing ware.
 
If you wanted to use bronze then leaded bronze is good with mild steel shafts and lower surface speeds as will be the case with your model. Many other bronzes are more suitable for use with higher surface speeds and hardened shafts such as phosphor bronze grades. Leaded bronze is very easy to machine, the lead content providing free machining qualities.
 
There would be little point in having a cast iron housing and fitting a bronze sleeve bearing, just stay with the cast iron on its own. Only if the housing is steel for example would you want to fit a cast iron or bronze bearing sleeve.
 
It won't apply here but FYI most bronzes are not suitable for high loads, the bronze can become deposited on the shaft due to the load, aluminium bronzes with hardened shafts are more suitable for heavy duty applications. Aluminium bronze is difficult to machine.
 
Nigel
 
 
Thread: Girder crown stays - are they overstressed?
20/12/2011 23:27:42
Hi Stub/Jason
I have subsequently included the cutouts in the girder and cross members. There is no change to the stress levels only some slight changes to the stress distribution as you would expect.
 
It's best to build up FEA in stages, then you learn more about the application and it makes it easier to resolve any FEA model problems.
 
Paul, this analysis is indeed a vindication of the original design work.
 
Seasons greetings and best wishes to everyone for 2013
 
Nigel
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