|
|
Post by builder01 on Aug 30, 2016 22:42:26 GMT
Hi Julian,
Glad to see you are back at it! I have been following your thread, with great interest, as suggested by yourself on another forum. Keep up the good work (and the show and tell!)
David
|
|
|
|
Post by Roger on Aug 31, 2016 8:17:39 GMT
On the far bottom right of the above pic is a very small dental burr. This is what I use as a centre drill for very small drills in most applications, though for very small work I have some special clock/watchmakers stuff. The smallest slocombe centre is far too big for a No.75 drill. If you get the centering OK then everything else is OK. I did this batch drilling from the base of the jets to top, whereas I think the last batch I did was the other way round. I test the blower ring on my boiler test rig to make sure the jets of water go the right way. The blower ring needs drilling the threaded jet holes at an angle - of which more anon when I do the blower rings. Cheers, Julian Just a thought Julian, a number 75 drill is 0.5334mm so not that small in the PCB industry. If you used a 0.5mm Carbide drill, you could hold it in a standard chuck because it will have a 1/8" shank, and the runout will be superb. You don't need a centre drill with these, they're so rigid that they centre themselves. Centre drills are never used in the PCB industry, even when drilling Copper, Aluminium or Brass. These types of drills are superior to the flimsy HSS variety in my opinion, the only thing you need to do is to feed them very slowly to avoid breakage. Here are some 0.5mm drills on eBay, 10 for £1.92 with free P&P. How do they do that? These are the sorts of drills I'll be using when I come to make the injectors. |
|
jma1009
Elder Statesman
Posts: 5,922
|
Post by jma1009 on Aug 31, 2016 9:14:46 GMT
Hi Roger,
Many thanks for the ebay link - order placed, plus a set of small HSS drills in 0.1mm increments for 99p!
I suppose the other detail required is a very good lathe tool set exactly at centre height so the drill or whatever centre being used can have a good start on a perfectly machined face with no 'pip'. I am very lazy and hate changing tools so use a small parting off tool I also use for injector stuff.
Cheers,
Julian
|
|
|
|
Post by Roger on Aug 31, 2016 10:14:21 GMT
Hi Julian,
Glad you found that useful, I'll be very interested to hear what you think of them. You need to think of them more like grinding bits than drilling ones, you won't often use high enough infeeds to get a continuous spiral of swarf. If you see that, you're probably risking breaking the drill. They're so sharp and rigid that I'd wager you'd be able to start a hole even on a pip if you make that initial touch a gentle one. I think you're going to be impressed.
I think a lot of us are fundamentally lazy when it comes to changing tools, chucks, arbors etc, and that's why I've focused on making that stuff really quick and repeatable. It does come with a high price tag though.
|
|
|
|
Post by Deleted on Aug 31, 2016 11:23:55 GMT
I too thank you for the link Roger...I have also ordered some for the future...  Pete |
|
jma1009
Elder Statesman
Posts: 5,922
|
Post by jma1009 on Sept 3, 2016 20:57:54 GMT
A bit more progress. The weather here today has been foul so an excuse to spend the afternoon and evening in the workshop... Here are some pics. The first is the blower ring bits. The larger one is for George's Butch, the smaller for Stepney. The joints overlap to start with to make silver soldering easier. Then after silver soldering up. Then my sketch I was working to. I managed to shave a 1/16" off the proposed OD of the one for Stepney so it has finished off at 13/16" OD. Both slide onto a rebate turned on the blast nozzle - as per the final pic of Stepney's on the loco.     All the jets are inclined inwards. Cheers, Julian |
|
|
|
Post by springcrocus on Sept 3, 2016 22:27:29 GMT
Julian, how about a picture of the underside of the blower ring so that we can see how it went together? There must be a steam space in there somewhere. Also, a description of your technique for getting the inclined angle would help many others, I'm sure.
Regards, Steve
|
|
jma1009
Elder Statesman
Posts: 5,922
|
Post by jma1009 on Sept 3, 2016 22:45:31 GMT
Hi Steve,
I can certainly take a pic of underneath tomorrow.
Ah, that all important inclined setting of the jets!
I clamped a bit of 15 thou shim to the pillar drill table which one edge of the top piece was held against whilst centering, and drilling. The tapping was done by hand.
I can strongly recommend the Laurie Lawrence design of blower ring with removable jets. Don Young never used it (hint, Pete!), but Martin Evans did later on.
The only problem with this design is on the accumulation test for the safety valves because the blower is so effective. However Stepney has a Gordon Smith safety valve which has already been exhaustively tested.
Cheers,
Julian
|
|
|
|
Post by runner42 on Sept 4, 2016 1:16:00 GMT
Hi Julian,
I am pleased that in your sketch you define every dimension, unlike LBSC who often omit dimensions and these have to be calculated (or guessed) from other defined dimensions. But I note that you haven't provided details of the nozzles, the important ones being I assume their height above the blower ring and the bore size.
Brian
PS Can you please expand on your comment that the accumulation test for the safety valves will be affected by the effectiveness of the blower. |
|
johnthepump
Part of the e-furniture
Building 7 1/4"G Edward Thomas
Posts: 494 
|
Post by johnthepump on Sept 4, 2016 8:31:45 GMT
Hi Brian, The accumulation test is part of the steam test. Where with a bright fire and the blower full on, the safety valve/s release the steam so that the boiler pressure does not rise 10% over the working pressure. This is fully described in the green book para 11.8 Our clubs Super Simplex built 1994 by members has one of these blower rings and passes its accumulation test and as I well recall Julian had a hand in the build. John.  Super Simplex by John The Pump, on Flickr |
|
|
|
Post by Deleted on Sept 4, 2016 10:05:35 GMT
Hi Steve, I can certainly take a pic of underneath tomorrow. Ah, that all important inclined setting of the jets! I clamped a bit of 15 thou shim to the pillar drill table which one edge of the top piece was held against whilst centering, and drilling. The tapping was done by hand. I can strongly recommend the Laurie Lawrence design of blower ring with removable jets. Don Young never used it (hint, Pete!), but Martin Evans did later on. The only problem with this design is on the accumulation test for the safety valves because the blower is so effective. However Stepney has a Gordon Smith safety valve which has already been exhaustively tested. Cheers, Julian hint taken...I may need a reminder when I get there, though... Cheers Pete |
|
|
|
Post by runner42 on Sept 4, 2016 22:36:04 GMT
Hi Brian, The accumulation test is part of the steam test. Where with a bright fire and the blower full on, the safety valve/s release the steam so that the boiler pressure does not rise 10% over the working pressure. This is fully described in the green book para 11.8 Our clubs Super Simplex built 1994 by members has one of these blower rings and passes its accumulation test and as I well recall Julian had a hand in the build. John.
Hi John,
thanks for the explanation, the reason for wanting clarification is that in the AMBSC Code Part 1 at para 7.2.6 an accumulation test is carried out under full firing conditions but does not mention operation of the blower. One could argue that having the blower on contributes to full firing conditions but I thought that the accumulation tests is testing the capability of the safety valves to release steam pressure at sufficient rate that it does not allow the pressure rise above 10%. I maybe wrong but I thought the blower would assist the safety valves release steam and should not be on.
Brian
|
|
jma1009
Elder Statesman
Posts: 5,922
|
Post by jma1009 on Sept 4, 2016 23:10:56 GMT
Hi Brian,
In the UK for the accumulation test the blower is turned on. The loco is stationary for the accumulation test, as I am sure it would be in Australia.
The LBSC type blower was pretty ineffective. The type I use is very effective.
I did describe the blower jet manufacture and sizing last weekend.
Cheers,
Julian
|
|
Lisa
Statesman
Posts: 806 
|
Post by Lisa on Sept 5, 2016 2:05:57 GMT
In the UK for the accumulation test the blower is turned on. The loco is stationary for the accumulation test, as I am sure it would be in Australia. There's always been full blower during any accumulation test I've been involved in or witnessed... and most of those were done by the (now former) chairman of the A.M.B.S.C. So I'm pretty sure it was the correct way, by code, to do it. That's certainly a better looking blower than the old pipe-pointing-vaguely-up kind that dad was always in favour of. |
|
|
|
Post by Jim on Sept 5, 2016 3:39:47 GMT
Hi John,
thanks for the explanation, the reason for wanting clarification is that in the AMBSC Code Part 1 at para 7.2.6 an accumulation test is carried out under full firing conditions but does not mention operation of the blower. One could argue that having the blower on contributes to full firing conditions but I thought that the accumulation tests is testing the capability of the safety valves to release steam pressure at sufficient rate that it does not allow the pressure rise above 10%. I maybe wrong but I thought the blower would assist the safety valves release steam and should not be on.
Brian
Brian the purpose of the blower is to create a draft through the fire box to help raise steam not vent it as in the case of the safety valves. Jim |
|
|
|
Post by springcrocus on Sept 5, 2016 6:53:51 GMT
I don't know anything about this stuff but I can see Brian's point: are you venting more steam by using the blower than you are raising by lifting the fire? One for the grease top hats to discuss, I think.  Steve |
|
|
|
Post by Jim Woods on Sept 5, 2016 7:14:51 GMT
According to the 2012 AMBSC we use in NZ, you must now use the compressed air/fan auxiliary blower you use to steam up with at full chat. This is to make sure you don't bleed off steam as mentioned above. I find all my loco's own blowers makes steam better than the auxiliary blower but as some would say, "them's the rules"
This has cause some discontent with our boiler inspectors. One of them feels even just using the steam blower flat out is terrible as you will melt the end off the superheater's. He decided that the safety valve accumulation test should be done by running the loco around the track with the blower hard on so as to admit steam through the superheater's. This has since been over ruled and as per the AMBSC now stands. Under the old code, it said that a loco could be set up on blocks and the regulator "cracked" to allow steam through the super heaters.
Jim
|
|
|
|
Post by Cro on Sept 5, 2016 7:27:30 GMT
I don't know anything about this stuff but I can see Brian's point: are you venting more steam by using the blower than you are raising by lifting the fire? One for the grease top hats to discuss, I think. Steve If this were the case then the blower wouldn't be doing a very good job.....? The sensible way to look at why this test is done (not the sole purpose) but is so that IF you were to leave the loco with the blower on full the safety valves would keep the boiler at a safe level and not let it rise above 10% of its designed and working pressure and that in this case you boil it dry and melt something before it goes "pop" at a joint with too much pressure. Doing this with an auxiliary blower to me seems completely pointless if you are considering this point as does running the loco whilst performing this test. Adam |
|
|
|
Post by springcrocus on Sept 5, 2016 7:33:58 GMT
What I meant was, for example, raise the fire with the blower then turn it off so you are no longer venting any steam. Would this contribute to the amount of steam raised and, possibly, take a previous borderline case over the safty limit?
As I said, I know nothing about any of this but the only way I will learn anything is if someone discusses it.
Steve
P.S. Sorry, Adam, I forgot to thank you for your input. It will be interesting to see if others follow your lead.
|
|
|
|
Post by runner42 on Sept 5, 2016 8:04:10 GMT
I was told by a SASMEE colleague that the LBSC Doris safety valves wouldn't pass the accumulation test because the vent holes are too few and too small. I assumed from his comments that this test is to solely test the efficacy of the safety valves, being to release at the correct pressure and to vent at a rate that is equal to the boiler ability to raise steam. If the boiler is capable of raising steam faster than the safety valves ability to vent this rate of steam generation then the pressure rise is too great. The blower is required to produce a draft to enable the fire to reach optimum heat generation which results in greater steam generation, this point is understood and it should be used to reach working pressure. However, the worst case scenario is when the fire is raging and the safety valves are blowing and then the blower is turned off so it doesn't contribute to venting steam from the boiler and the safety valves are solely responsible for this. The blower can be very efficient and produce more draft thus more heat but the penalty is that it uses more steam, thus the blower is a variable and whether its open fully or partially cannot be determined during use. The safety valves however are the sole safety device.
Brian |
|
