Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1] 2 3 4   Go Down

Author Topic: Marcher Build  (Read 16409 times)

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Marcher Build
« on: September 05, 2017, 05:29:08 pm »

I have started a Marcher steam Engine with the intention of fitting it into a relatively small boat. So far, I have drawings and after encouragement from George (ooyah/2) have completed the crank shaft which I view to be a crucial part. Given a shaft and big-end journal size of 1/4" such an off set gives an overlap that complicates the fabrication of the crankshaft, hence the need to machine from one piece.
The photos shows the sequence that I adopted, I am sure others may have alternative approaches. Photo 1 shows the 3/4" bar faced and centred, then transferred to 'v' blocks to mark out the off-sets of 7/32, 90 deg. apart. Subsequently centres were drilled and the opportunity to mark distances between webs. Before mounting between centres I took the opportunity to remove a lot of material whilst held securely in the 3 jaw chuck before mounting between centres. It was necessary to leave bosses at either end to accommodate the centres. The greatest difficulty was getting cutting tools into and between the  crank webs. Using such small tools means very small cuts and feeds and slow progress! Once the big end journals and web faces are finish the boss at the ends can be removed in conjunction with taking the shaft to its final dia., as the final photos shows. Let's see what other challenges lay ahead and the build continues!


Ian
Logged

xrad

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 602
  • Keeper of the Sun Dried Tomato
  • Location: Ohio USA
Re: Marcher Build
« Reply #1 on: September 05, 2017, 07:38:38 pm »

First, great job. Nice crank.  But it looks like your centering holes are off compared to scribe lines?

How do you mark both ends of rod in exactly the same location for the two offset centering holes(with one end in the chuck)?  If rod was on a flat plate and a line scribed at each end through dead center(parallel to plate)...then roll rod 90 degrees and scribe a second line through dead center at each end...... then another scribe done 'x' distance from center(this time without rolling rod)parallel to plate on both ends...then rolled another 90 degrees and final scribe line done on both ends 'x' distance and parallel to plate... the marks would be pretty close at both ends....


ideas?
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #2 on: September 05, 2017, 09:33:06 pm »

Hi,


I am very pleased with the end result. First all I believe that the camera angle is giving a distorted view of the scribed lines and the centres. Regards scribing the lines; first step face and centre drill the bar at both ends. Remove from lathe and mount and clamp on 'V' blocks resting on surface plate. (1) Scribe line thro centre height at both ends. (2) Set surface gauge to 'off-set distance and scribe a further two line parallel to the first two at each end. (3) Release clamps and rotate 90 deg. with the aid of a square off the surface plate. (4) With the surface gauge at the same setting scribe a further two line at 90  deg. to the others. You now have two off-sets marked at either end same distance from the centre. (4) With the aid of sight glass centre pop the centres and whilst still clamped within the 'V' blocks drill the centres. Given than the centres in the lathe (dead centre, head stock end and Live centre at tail stock end) are in alignment the the shaft will be tuned parallel. Hope this explanation helps with what I did.


Regards


Ian
Logged

xrad

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 602
  • Keeper of the Sun Dried Tomato
  • Location: Ohio USA
Re: Marcher Build
« Reply #3 on: September 05, 2017, 10:53:58 pm »

Thx for reply Ian.  Yes, it is a nice smooth looking crank.  Any need for counterweights while turning?
Logged

steamboatmodel

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 346
  • Location: Toronto, Canada
Re: Marcher Build
« Reply #4 on: September 06, 2017, 03:31:03 am »


A very good job on the shaft, I think I would have gone with a fabricated one.
Gerald.
Logged
Be wary of strong drink. It can make you shoot at tax collectors--and miss. Lazarus Long

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #5 on: September 06, 2017, 09:53:57 am »

Gerald,


The 1/4" crankshaft and that of the 1/4" big end journals overlap each other which complicates the way a fabricated component.
In the conventional way, the main shaft is left in place until the end of the construction at which time the parts between the webs are removed. However, the main shaft and big ends have already 'broken into' each other. Hope this makes sense. Either way, I had a desire to have go at machining one from solid.


xrad,


No I didn't use balance weights. However, I did reduce the dia. of the main shaft quite considerably, thereby reducing its overall weight which helped any out of balance affects when turning the big ends. It remains a compromise however as if main shaft becomes to slender at an early stage it may flex.


Ian
Logged

ooyah/2

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 757
  • Location: Glasgow
Re: Marcher Build
« Reply #6 on: September 06, 2017, 11:55:27 am »

Gerald,


The 1/4" crankshaft and that of the 1/4" big end journals overlap each other which complicates the way a fabricated component.
In the conventional way, the main shaft is left in place until the end of the construction at which time the parts between the webs are removed. However, the main shaft and big ends have already 'broken into' each other. Hope this makes sense. Either way, I had a desire to have go at machining one from solid.


As Ian has said there is a foul on the crank shaft centres, and to make it as per the drawing it's impossible to fabricate it and that's I why when I made the Marcher shaft I reduced the diameter to7/32" and increased the throw to 7/32" + .010" which allows you to cut thro' the piece of the shaft that isn't required.


George.
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #7 on: September 14, 2017, 04:48:09 pm »

I have done a little more; machined the two eccentrics. I say two, because it is still my aim the make the piston valve version and unlike the slide valve version that employs Stephenson reversing gear that requires two pairs eccentrics (a total of 4), the piston version only needs two. Reversing however, is achieved by a control valve that redirects the steam. I find the control valve rather large and out of proportion to the rest of the engine, so it's my intention to complete the control valve first. If I don't like the look of it I will abandon the idea and build the slide valve version. The size and position of the ports in the cylinder head are slightly different between the two versions, so the decision can be put off until machining of the cylinder head progresses.


The photos show an eccentric set up in the chuck that allows the off-set bore to be drilled and the boss turned. The others are the completed eccentrics. As an alternative to setting up the eccentrics in a 4 jaw chuck and using a DTI to set the off-set, I used the method of using an appropriate size packing piece in a 3 jaw. it is the first time I have used this method and it proved to be very straight forward once you get the packing piece to the correct size. The actual thickness of the packing is proportional to the  off-set and the O/D of the eccentric. I will post the formula that I used for those that are interested. I understand they are a number of variations of the formula all along the same theme, but the end results are so minor they can be discounted for most purposes.
Logged

steamboatmodel

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 346
  • Location: Toronto, Canada
Re: Marcher Build
« Reply #8 on: September 14, 2017, 10:42:03 pm »


I wasn't aware there was a formula, I always just sketched it out and tested on scrap until I got it right.
Gerald.
Logged
Be wary of strong drink. It can make you shoot at tax collectors--and miss. Lazarus Long

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #9 on: September 15, 2017, 11:25:53 am »

I understand that there are various formulas out there and the "Model Engineers Handbook' (don't have a copy) has one.
[/color]
[/color]The simplest formula is just
[/color]
[/color]Packing = offset x 1.5
[/color]
[/color]For 5mm off-set this would give:
[/color]
[/color]P = 5 x 1.5 = 7.5mm
[/color]
[/color]But the following formula gives a slightly more accurate result whilst not being too complicated.
[/color]
[/color]Packing = 1.5 x offset x (1 - (1/8 x (Offset / Bar Diameter))).
[/color]
[/color]For this example it would give:
[/color]
[/color]Packing = 1.5 x 5 x (1 - (1/8 x (5 / 22))) = 7.29mm
[/color]
[/color]This means that a piece of packing of 7.29mm against one jaw of the 3 jaw chuck should give the required offset of 5mm.
[/color]
[/color]It's best to create a speed sheet, I created simple spread sheet in both imperial and metric that just requires the values to be entered. I am sure there are others who rely on other versions and get satisfactory results.

Logged

Tug-Kenny RIP

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,625
  • Location: Newport. S Wales
Re: Marcher Build
« Reply #10 on: September 15, 2017, 05:08:40 pm »


You definitely didn't want colour there then.   {-)

Logged
Despite the high cost of living   .......... It remains popular

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #11 on: September 16, 2017, 12:21:10 pm »

I cut & pasted the text in from another document, no idea where the 'color' came from!
Logged

Baldrick

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,414
  • Model Boat Mayhem is Great!
  • Location: Nether Effingham (Perfideous Albion)
Re: Marcher Build
« Reply #12 on: September 16, 2017, 08:25:17 pm »

I cut & pasted the text in from another document, no idea where the 'color' came from!


 Probably America , lots of words they can't spell properly.
Logged
And everyone thought it was IVAN who was terrible

xrad

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 602
  • Keeper of the Sun Dried Tomato
  • Location: Ohio USA
Re: Marcher Build
« Reply #13 on: September 16, 2017, 10:28:14 pm »

Probably first from Europe and translated to current HTML format in USA ...... :-))
Logged

Tug-Kenny RIP

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,625
  • Location: Newport. S Wales
Re: Marcher Build
« Reply #14 on: September 17, 2017, 10:01:12 am »


Oh , we do like a giggle on here.

Logged
Despite the high cost of living   .......... It remains popular

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #15 on: September 23, 2017, 02:30:19 pm »

The build continues with the machining of the eccentric straps. A 'stick' of cast gunmetal is provided, the rough bores are oval in shape. However once drilled, split into two by sawing, faced and bolted together the bores become more circular. Mounted in 4 jaw chuck they are then bored out to the finished size of 1/2". I then mounted them on a mandrel and faced both sides almost to finished size. I left a very small spigot on the faces to indicate the final radius/profile to act as filing guide. An operation I carried out whilst still held on the mandrel. Others may prefer to use a rotary table and milling machine. I however find a degree of hand finishing satisfying. Once the outer profile is formed, the mandrel is returned to the lathe and the straps taken to final thickness. The oil pockets and drilling for the connecting rods remains to be done.
Logged

bfgstew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 502
  • Comfortably Numb
  • Location: Retford (Robin Hood Country)
Re: Marcher Build
« Reply #16 on: September 23, 2017, 03:47:11 pm »

I do love quality workmanship........... :-))




Stewart
Logged
"Give me a ping Vasili. One ping only, please"

xrad

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 602
  • Keeper of the Sun Dried Tomato
  • Location: Ohio USA
Re: Marcher Build
« Reply #17 on: September 23, 2017, 09:41:38 pm »

Slitting saw, band saw? What blade thickness?  Thx
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #18 on: September 24, 2017, 11:38:17 am »

Hi xrad,


I drilled clamping holes, then split the casting with a slitting saw of 1/16" thickness. The mating faces were cleaned up in the mill, only requiring a very light cut. Once clamped together ovality of the original casting virtually disappeared. A band saw would have worked just as well, although I don't have one. Equally, careful cutting through by hand always remains an option.


Ian
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #19 on: September 24, 2017, 03:51:57 pm »

Started on the bedplate. Straight forward operation on the milling m/c to achieve the two heights; i.e. overall height and that of the step height of the pads that support the bearing blocks plus a little filling in order to clean up the casting. An alternative method would have been to mount in a 4 jaw and face off in the lathe.
The critical thing is the marking out of various locations/drillings of the bearing blocks and the 4 support columns. These need to be both parallel to and at right angles to the centre line. I achieved this by fixing the bedplate to an angle plate that is ground square. With the aid of surface gauge and surface plate, marked one set of lines, turned the angle plate through 90 deg. then marked out the others.
Logged

ooyah/2

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 757
  • Location: Glasgow
Re: Marcher Build
« Reply #20 on: September 24, 2017, 07:07:44 pm »

Hi Ian,


Very neat and looking good, one thing that I will say about Reeves Castings is that the ones that I have used machine beautifully without blow holes.
I look forward to further progress with your Marcher.
When I made my Marcher I fabricated a base plate from sheet brass with pads soft soldered on and extended the base plate to take an engine driven pump.


George.
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #21 on: September 25, 2017, 11:52:37 am »

Hi George,


I agree, the Reeves castings are pleasure to work with. I suspect that, I too may need to fabricate an alternative baseplate as it may be a better option when fitting it into a boat. In the meantime the present baseplate can act 'test bed'.


Ian
Logged

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #22 on: September 26, 2017, 01:27:47 pm »

Next step the main bearings. Housing blocks are cut from ms flat bar, machined square, drilled and bolted together. Bearings are phos bronze machined from hex bar. The drawing calls for 3 no. with no mention that the centre one clearly needs to be split. Did this by soft soldering two halves of hex bar together and machined them in an identical way to the other two, then warming them up to split.
Mounted the housing blocks in 4 jaw, drilled and bored out to suit o/d of bearings. Don't have one of those spring loaded centring things that can be used in the tailstock chuck. But, do have a dead centre with a centre in the rear end. I find if the centre is placed on the centre mark of the component in the 4 jaw and lightly held in-place by the tailstock centre then the run-out can be adjusted (i.e. centred )using a DTI in the convention way. Next thing the fitting of all component onto the bedplate and get the shaft to turn nicely.
Logged

Mark T

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,087
  • Location: Dudley in the Black Country
Re: Marcher Build
« Reply #23 on: September 26, 2017, 07:23:58 pm »

You’re making a really nice job of that Ian and you use the same centring technique that I have always used. I have always found it to be accurate and easy.  Keep the updates coming

IanJ

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 102
  • Model Boat Mayhem is Great!
  • Location: South Somerset, UK
Re: Marcher Build
« Reply #24 on: September 27, 2017, 09:05:40 am »

Thanks Mark.



Logged
Pages: [1] 2 3 4   Go Up
 

Page created in 0.098 seconds with 21 queries.