Here is a list of all the postings Dusty has made in our forums. Click on a thread name to jump to the thread.
|Thread: darjeeling locomotive|
Having just read the latest instalment of this series I have noticed that the drawing for the main spring shows the thickness as 0.78. Ray says that it is masive and would be rigid in the model, that is an understatement. By my calculation the thickness of this spring should be 0.054. How did I arrive at that, The spring on the original is 3/8" or .375, if you use a divisor of 6.85 this will give you 0.054. Why 6.85, this is arrived at by dividing 24" (the gauge of the original loco) by 3 1/2" (the gauge of the model). By the way the remaining springs in the stack are 5/16" thick or 0.045 in model terms.
|Thread: Darjeeling photos uploaded|
Yes, I aknowledge that I am a bit thick, but how do I access these photo's. Can someone direct me on the right path please.
|Thread: Centring a rotary table horizontally on a mill table.|
I agree in some part with Bogs assesment of your problem. I think the problem is with your gibs, I believe that your gibs are set too slack. You can check the play in the table by locking everything up lashing up a clock on the end of the table and giving the opposite end of the table a bit of a push and shove having slackened the lock. This should show how much slack is in your gibs. Theoretically if you removed the leadscrew and pushed the table up and down you should feel resistance, it should feel quite stiff. When applying the locks you do not need to torque wrench them up, just a nip should suffice. This will also help with your ordinary milling. Locking everything up and then tapping the rotary table into position is making hard work of a simple task.
|Thread: repeated postings|
What you are seeing is contributors adding to your original post. When this happens the forum is showing the date and time of that posting. As you are well aware we do not own the thread that we create, and it can be hijacked. This means that it can, and often does go off at a tangent to the original posting. As far as I can see there is nothing that can, or should be done to alter this. This is after all a forum for the exchange of ideas,and a point where help from more knowlegable members can benifit us all. We can all learn, even from the newest beginer. See I have hijacked the thread and gone on a rant
|Thread: darjeeling locomotive|
I am afraid that a lot of you seem to be missing the point. In effect the back to back dimension means nothing, it is the thickness of the flange and the measurment over the flanges that is important. This measurement has to be less than 3 1/2" by, I would say 1/16". This is to allow the loco to run on the tread of the wheel as oposed to tight on the flanges. The larger the radius between the flange and the tread then the nominal 1/16" needs to be larger. In essence the thicker the flanges the smaller the back to back dimension needs to be.
Playing the devils addvocate, if for instance we had a back to back dimension as per Martin Evans of 3 9/32" and flanges of 5/32" The loco would not sit on the track. I am afraid I cannot advance this any further. Everything in life is a comprimise especially Model Engineering.
I forgot to say that the wheels of my Loco are in fact 43/64 wide, even wider than Darjeeling Loco
I am sorry if my reply confused you. What you must remember is that this Loco is scaled at roughly 1 3/4" to the foot. The wheel standards you are quoting apply to locomotives that are scaled at 3/4" to the foot. My current Loco is a 3 1/2 N.G. Loco. My wheel back to back dimension is 3 5/32", the flange is 1/8" wide, simple maths show that this gives a dimension of 3 13/32. A whole 3/32" narrower than the nominal 3 1/2" gauge track. I did not say as designed this loco would not run on 3 1/2" track, but there is a real danger that it would have a propensity to de-rail. I think that when I get round to building I will reduce the width of the flange to 1/8" this would in someway overcome the potential problem I have highlighted, without the need to completely redesign the axles. I dont know how Ray has got on with his loco, a lot depends on the accuracy of the gauging of his track.
re Dave Harris's post
Wheel standards do not apply to narrow gauge loco's. You must read the back to back dimension in conjunction with the flange dimension. Flange dimensions on narrow gauge loco's are far more substantial than main line loco's. If Martin Evans standard were to be applied to this loco the wheels would run on the flanges if run on a standard 3 1/2 gauge track. This would give an inside flange dimension of 3 19/32" patently 3/32" wider than the track. Hope this explains your query Dave. (yes I know I am not the Editor)
I have looked at the axle drawing and am of the opinion that the wheel back to back dimension is wrong. These are my reasons; The axle is 3 and 3/16ths for the back to back dimension added to this is the width of the flange x 2 =5/16 added to the previous 3 3/16 = 3 1/2".
this is far to tight for a normal track let alone one where the gauge may be a little tight. The effect of this would be to cause the wheels to climb the track thereby derailing the loco this would be very evident on curves. The dimension should be, in my humble opinion no more the 3 1/8 for the back to back dimension.
It would also improve running if the wheels were coned by about 2 degrees, this would help centralise the loco on the track. I am ready to be shot down in flames.
Hi to all who are building this Loco.
Just a reminder to those of you who are using 3mm plate for the frames to compensate for the slight difference in thickness from 1/8" plate. If you make the front beams and the angle which joins front and rear frames together 15thou wider and also the axleboxes 7thou narrower where they fit through the frames, you could save a lot of heartache later remembering to make compensation in valve gear components, fly cranks, cylinder bolting faces etc etc etc. No, I have not started building yet, another project to finish first, Then I will start. You may not think that such a small difference can affect the loco, I can assure you it can, having built a narrow gauge o/s frame loco I speak from experience. From what I have seen it appears that leaving the rear frames as the are will not matter, allwats remembering to adjust the joing braket fabrication.
|Thread: The use of adjustable reamers|
I fear I am or about to be a prophet of doom. Be very careful of the grade of phos you use for these bearings if you intend to ream them. Drawn Phosphor Bronze is an absolute B****** to machine it has a tendency to grab drills and reamers. Try to get something like colphos or perhaps a leaded bronze. These will, I feel sure suit your application. They are much friendlier to machine.
Adjustable reamers are a repair tool, I would not advocate their use for sizing a hole to a specific size. It is better that a hole is bored to size. In use the reamer is adjusted (by means of the collars at either end of the reamer) to just and I do mean just scrapes metal from the hole. The reamer can then be adjusted by slacking of the collar at the end nearest the square by say 1/16th of a turn and the tightening the collar at the other end. repeat until the hole has been cleaned up or has reached size. Do not be tempted to take a larger cut as adjustable reamers have a tendency to dig in, this if it happens leaves a hole nicely out of round. Do not attempt to ream a hole that is out of round to start with. It is far better to run a drill through the hole to make it round before you start.
Hope this helps. Dusty
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