Author Topic: Sweet Pea build  (Read 13788 times)

Online sco

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Re: Sweet Pea build
« Reply #30 on: January 26, 2021, 08:24:46 PM »
Really like the methodical approach with the jig and fixtures  :ThumbsUp:

Simon.
Ars longa, vita brevis.

Offline Barneydog

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Re: Sweet Pea build
« Reply #31 on: January 26, 2021, 08:33:39 PM »
Thanks Simon.

I dislike making parts that then sit in a box until they are needed. Most of my projects are machined in the build order. I am following Jack Bucklers build book because he has written it in the way I like to work. The book is nearly worn out by the number of times I have read it in preparation for the build. It went with me on my last couple of holidays so has been to the Caribbean and the Far East! Its certainly travelled a few thousand miles!

I can take no credit for the jig as it is in the book but I agree with Jack Buckler.  It is worth the extra time to make the jig even though it is not likely to be used again.

I have a few mods I want to make and they will be inserted at the appropriate times.


Cheers

Julian

Offline Jon Cameron

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Re: Sweet Pea build
« Reply #32 on: January 26, 2021, 11:25:23 PM »
Loving the work so far, look forward to more instalments  :popcorn:

Offline Barneydog

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Re: Sweet Pea build
« Reply #33 on: January 30, 2021, 09:29:15 PM »
Hi Guys,
Had an hour or two outside today so completed the crank pins.

I had done one the other day so completed the second drive pin for the rear wheels. These have two journals. One for the connecting rod and one for the drive rod from the crosshead. The journals are 1/2". The tip is reduced to 3/8" to accept the crank which also holds the drive rod in place. This will be made later at the appropriate time.
The pins on the front wheels are a single as they only have one rod. This journal lines up with the same one on the rear wheels and is used for the connecting rod. The end is reduced to be a good fit in the wheel being individually checked to suit one wheel. This allows for any inconsistencies in the drilling and boring of the crank holes in the wheels. The centre is further reduced by 0.25mm to allow glueing with loctite.

Two pins are made and cleaned.
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All four pins sit nicely in their respective wheels.

I have in the pipeline an adjustable jig for the setting and quartering of loco wheels. Because the pins are a smaller diameter than the axle I drilled and bored out a short length of axle bar to make some sleeves.
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They are bored to a good fit in the pins but not too tight. They need to be easily put on and off.
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The sleeves are not immediately needed but this was an obvious time to machine them while the pins are still loose and the lathe was already set up. They will be kept for later. I will build the jig later this week so you will see more then.
I have completed a couple of brackets for the weigh shaft that will be fitted later. The brackets bolt onto the inner face of the rear axle boxes so now was the time to make them.

Couple of pieces of 3/16" steel drilled in two places. One at the centre of the axle and one 4.5" from the bottom of the axle box and 3/16" to the rear of the centre of the axle.
They were clamped together and drilled to 6mm. Two M6 nuts and bolts hold them together. The large washers are used to cut and grind the top down to the profile of the washers. The sides are grinded to a slope from the top of the axle box to the side of the top washer profile.

The bottom hole is drilled out to larger than the axle for clearance. Two cuts are made from the bottom edge to the edges of these large holes and files to shape. This gives room for the axle and a slot for the plates removal once fitted.
Holes are drilled 3.2mm on the plates to suit the axle boxes. They are sited to avoid all other drillings on the axle boxes. It is tight but planning the previous drilling on the axle boxes made this possible. The plates were clamped on the axle boxes and the holes were transferred. The boxes were drilled and tapped to accept M4 bolts. The plates were drilled out to 4.5mm to got clearance for the bolts and a very slight adjustment.
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The brackets will be further cleaned and buffed before being sprayed and fitted. Bushes need to be fitted in the top holes but need to be made to size for the weigh shaft.
Next job will be the cranks to fit on the crank pins.
I need to also turn the axle water pump eccentric and strap so the axles can be fully assembled and quartered. Soon hopefully!!


Cheers Guys

Julian

Online Kim

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Re: Sweet Pea build
« Reply #34 on: January 31, 2021, 05:48:14 AM »
Nice work, Julian!  Enjoying your build  :popcorn: :popcorn:
Kim

Offline Barneydog

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Re: Sweet Pea build
« Reply #35 on: January 31, 2021, 06:44:59 PM »
Thanks Kim glad you are enjoying it.

Hi Guys,

Started on the return cranks today. Couple of bits of 3/16" mild steel 3/4" by about 3". I stuck a piece of masking tape on the face of one bit to mark it.

The end holes have to be exactly 1.5" centre to centre. The middle hole needs to be on a straight line between the two about halfway. I drilled the centre hole 3mm and the end holes 6mm. I bolted the two plates together with M6 nuts and bolts in the end holes.

The nuts and bolts helped set the height when mounted in the mill vice. Machined both sides to my markings. I drilled the bigger hole out to 8mm and replaced the 6mm bolts with M8 nut and bolt and a couple of washers the size of the curve of the end. I put some washers on the M6 bolt at the other end. Using a flapwheel on my grinder and a file I shaped the ends to the profile of the washers with a taper in the centre between them. Using a decent junior hacksaw I cut down from the large hole along the centre line to the 3mm hole drilled earlier in the middle. About half way along this cut I drilled through the side of the plate at 2.5mm. This was opened out to 3mm on one half as far as the cut. The 2.5mm was tapped through to M3.

The 6mm hole was reamed out to 1/4" and the large one opened out and reamed to 3/8". This was done in the drill press so the holes are square to the face.
I filed and cleaned up the cranks ready for either painting or more probably nickel plating. An M3 bolt through the tapped holed tightens the crank onto its pin.


They fit nicely onto the crankpins and look well on the wheels though not fixed yet.


The pins for the smaller hole will be made and fitted in due course.

Cheers

Julian

Offline JC54

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Re: Sweet Pea build
« Reply #36 on: January 31, 2021, 09:35:07 PM »
I have to replace one of these parts on Metre Maid as it has been run loose and keeps detaching itself. :facepalm: Really enjoying this build keep it coming please. :old: :DrinkPint: :DrinkPint:
                               John
When the Fun Stops,, Stop!

Offline Barneydog

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Re: Sweet Pea build
« Reply #37 on: January 31, 2021, 09:37:57 PM »
Hi John.

Thanks I will keep going.

Which part have you got to replace?

Cheers

Julian.

Offline Barneydog

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Re: Sweet Pea build
« Reply #38 on: January 31, 2021, 10:34:34 PM »
Hi Guys,

Sitting here looking at the return cranks I am wondering how much wear there is going to be on the 1/4" hole and its pin. While it is not yet fitted I am now tempted to enlarge the hole and reduce the pin slightly so I can press in a small bronze bush. The pin could reduce from 6.3mm to 5.5mm. The hole could be enlarged to 8mm. A bronze bush 8mm diameter with a 5.5mm hole should give better wear. The wall would only be 1.25mm thick but should cope. It could go to 1.5mm if I reduce the pin to 5mm and use some stainless for added strength.

Got to be worth considering. Anyone got any opinion or experience of wear on this joint?

Cheers

Julian

Offline Barneydog

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Re: Sweet Pea build
« Reply #39 on: January 31, 2021, 10:49:40 PM »
Just realised my last post was the result of a brain fart. The pin is pressed into the return crank. The bush is on the vibrating lever that is moved by the return crank :shrug: :hammerbash: :Doh:

Cheers

Julian

Offline Barneydog

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Re: Sweet Pea build
« Reply #40 on: February 01, 2021, 07:52:29 PM »
Hi Guys,

Made the pins for the small end of the return crank this afternoon. Had my first covid jab this morning so got outside this afternoon.
For a decent pin that should wear well I decided to use some stainless I have acquired. It is chrome plated so needs some work to get through that but once through the stainless is very nice and machines well. These are the offcuts from some materials used for the R&D job of a friend of mine who is currently designing parts for the ejector seats on fighter jets. Obviously it is of excellent quality. I have several pieces set aside for various parts on this loco and the next.
On the prototype Sweet Pea the vibrating lever is held onto this pin with a washer and a spring pin. I have decided to thread the end and use a stainless washer and an M5 stainless locknut.

The first 12mm is reduced to 5mm then tapped M5. The next part is turned down to 1/4" to suit the return crank for a distance of 7/16". It is turned so it is a good press fit. I cut it off with 3mm spare and turned another one. They were then reversed in a 1/4" collet to turn the head, This is left at 5/16" and is 1/16" wide. Both were polished up and labeled for their corresponding crank.

Both had a washer and a nut put with them and were bagged ready for later use. They cannot be pressed in until the cranks are set and glued in.

Next job was to find the correct setting on the rear wheels for the cranks. They have to be exactly 180 degrees opposite the crank pins in the wheels. Both wheels need to both be set the same. In the build book a simple jig is made but the sizes used do not suit my axles. I have deviated slightly from the design sizes.
As I could not be bothered to work out the new sizes for a jig I chose a different route. In the lathe I turned two odds of mild steel to just fit the axle and drive pin holes. They were cut to length to fit within the thickness of the wheels. The ends to be used for this job were turned with the tool set exactly to centre height. This left a very nice centre mark.


Once in a wheel a steel rule was lined up exactly along these two centre points and a scribe used to mark the wheel.

This left a very accurate mark on the wheel at exactly 180 degrees.
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This mark will be used for crank setting in the next few days.
With nothing more to do to the wheels today I have taken this opportunity to paint them as cleaning the edges will be easier without the crankpins in the way. I used smooth black hammerite.


Once dry the excess will be removed from the faces to give a sharp edge to the paint. I painted the back aswell to keep the dreaded rust at bay.
I decided to start on the eccentric strap for the water pump as I need the eccentric to fit to the axle before I fit the wheels onto the axles. The strap is a bronze casting which was mounted in the four jaw on the lathe and faced both sides until it was down to a thickness of 1/4"

The white ring behind it was a plastic holder for plumbers pfte tape which I used as a spacer.

Next three lines were scribed on. One at the eventual centre and one at 1/32" on each side.
The strap was set in the mill vice with the centre line exactly aligned with the vice jaws.

All the faces were machined to size. The two outer faces where the clamp bolts will go were both machines to the same height to give a level to work to. The strap was then turned over in the vice.

The strap was set in the wice on two lengths of 1/8" tool steel. This means when the opposing faces are machined to size they are dead on parallel.

You will notice a bit of damage inflicted by the mill. As it is prone to do the bronze grabbed the mill cutter and tried to re-machine itself!

Luckily or hopefully it should be just out the way of the eccentric but we will see.
Next will be the drilling of the clamping bolt holes, cutting the strap in half and its boring out. I decided this could wait until tomorrow to save more damage.

I apologise again for mixing measurement units I prefer metric but use imperial when the design requires them. From the book or the plans there is no point in converting for use.


Cheers

Julian
« Last Edit: February 01, 2021, 07:58:47 PM by Barneydog »

Online propforward

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Re: Sweet Pea build
« Reply #41 on: February 01, 2021, 11:26:57 PM »
Lovely finish on those pins - any idea what stainless alloy that is? What rpms are you turning at if you don't mind my asking?

Unfortunate about that miller grabbing - but it is very grabby material!
Stuart

Forging ahead regardless.

Offline Barneydog

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Re: Sweet Pea build
« Reply #42 on: February 01, 2021, 11:48:32 PM »
Hi Stuart,
Thanks for your comment.

I believe it is some sort of 316 and it is chrome plated so things slide easily on it. It is the piston slide rod for some explosive ram. It handles acceleration of 0-60mph in less than a foot in something like a second or less. I am not over fussy if it machines well, suits my needs and of course is free. He gave me some titanium this time but not found a use for it yet---I will at some point I am sure!
This stainless machines ok at a slower speed of about 400 rpm. My lathe has stress compensation so you can hear it working and increasing the speed by 20-30rpm to cope with torque. Slow very shallow cuts come off as beautiful long springy curls that don't break. Taps ok with some tapping grease with a standard die. Just needs a push to start. Cuts with a fine hacksaw once through the chrome. The chrome will take the point off a new insert. Needs decent drills to drill it. No chance drilling the chrome even with my cryo-hardened drills that are saved for stainless only. Turning this size much above 400-450rpm doesn't cut so well and blunts the tip in no time.

My Chester lathe has the gears and the gearbox to drive the leadscrew so well there are no 'thread' lines. It is near enough smooth. I can also drive it in either direction while still cutting correctly.

I was too impatient to change the mill tool. The one on it is an excellent tool and cuts most materials well. I should have changed it for something finer as the large flutes and big teeth grabbed. Will remember next time I mill bronze.

Cheers

Julian

Offline Barneydog

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Re: Sweet Pea build
« Reply #43 on: February 07, 2021, 01:55:47 AM »
Hi Guys,
My Mum has come out of hospital today after the operation to repair her hip. I have spent several hours putting things in place to allow them to let her go home. Now that is all done I have been able to resume work in the workshop. I have spent a couple of afternoons finishing my quartering jig. At this moment I cannot show you too many details as I have written it as a construction article for one of the model engineering magazines.
I have now completed the strap and eccentric for the axle pump. Previously I had reached the point of cutting the strap.

The strap was located square in the pillar drill and both ends were drilled to 4mm. I then cut across the centre line previously marked.

Using a couple of M4 cap head bolts both arts were bolted together.

This assembly was mounted centrally in the four jaw vice and bored out to the design radius of 7/8".

The strap will need cleaning up but this can wait until later.
The next job is the eccentric. The strap MUST be machined before the eccentric as the eccentric has to be machined until the strap fits well. The eccentric cannot be removed from the lathe until it is completed. The eccentric is machined in the three jaw chuck to the correct outer diameter of 2". The eccentric is then moved to the four jaw and drilled and bored to fit the axle. This hole is offset from the centre of the eccentric by 5/16". Two holes are drilled from the outer face to the axle hole at about 90 degrees. These are for fixing screws which are M4 stainless steel grub screws. These screws are used to fit the eccentric onto a short length of the axle steel. Once fitted together they are mounted in the four jaw chuck so the eccentric rotates centrally on the chuck. Using my rear mounted parting tool I machined a slot in the eccentric to fit the strap. This is approximately 1/8" deep and 1/4" wide. Machining was gradual until the strap was a smooth fit.

Once completed the whole assembly was removed from the lathe.

All parts are completed for now but will next need cosmetic adjustments.

I machined the strap so that it was narrower so that it looks smaller and better against the eccentric. The pump face of the strap has been drilled and tapped M4 ready for the fitting of the axle pump rod..

Next job will be the quartering of the wheels.

Cheers

Julian.





Online Kim

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Re: Sweet Pea build
« Reply #44 on: February 07, 2021, 05:43:07 AM »
Glad your Mom is now out of the hospital.  That's never fun :(

Nice work on the eccentric and straps. They are looking very good.  I'm looking forward to seeing how you do the quartering.  That's going to be coming up for me soon in my A3 build!

Kim