(F) Skips the Hard Way

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Bilco
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(F) Skips the Hard Way

Postby Bilco » Sat May 10, 2008 11:13 am

One of the first questions I asked when I found the Gnatterbox was what the best V-skips to use in this scale were. It seems to be a common query from people starting out here! I searched various threads on the Forum and found lots to think about -- Slaters 1:32, Bachmann, Thomas Yorke, Gnomy grafted onto Sidelines. All good stuff but strangely unsatisfying -- though I might have changed my mind if I had seen this thread:

http://forum.gn15.info/viewtopic.php?t= ... 3ad2ca0d03

I bought a Gnomy skip at the 7mmNGA AGM to see what they were like -- I quite liked the skip bit, and the cost was low enough to be able to throw the rest away without any worries, so I bought some more. I consulted the Guru of the Southwest and he mentioned the Lokfuehrer Lukas products -- a visit to the web site showed that the skip frames were what I was after, even though they are 1:32 [2013 Edit -- now out of production]. After a bit of negotiation with Helmut, I bought the plastic version -- Helmut tried to get me to buy the brass ones, which probably would have made life a lot easier, but I never seem to take the easy route when I can make it complicated. I just got the basic chassis as I already had the Gnomy skips.

So now I was sorted -- Lokfuehrer Lukas skip frames, Gnomy skips -- and no way of joining the two together. Never mind, time to press on regardless, as the song has it. Helmut's skip chassis is described on Harald's web site:

http://www.die-kiels.org/snoeffel_kipplore_eng.html

It is made of what Helmut calls 'polystyrol', and the instructions say it should be glued with Blitzkleber, which I took to be Superglue. The instruction sheet is in German, so I ran it through Babelfish, with sometimes hilarious results. I made up a 'jig' -- two pins stuck in a piece of MDF -- laid the first layer over the pins, smeared one face of the middle layer with CA and laid it on top. I particularly liked the idea of putting a brass bar along the center rib to give the chassis some weight -- that was glued down, then all upper surfaces were smeared with CA and the top layer laid on. A weight on top helped keep everything flat and tight, and the frame could be taken off after an hour drying time and the next one done.

At this point the instructions call for the axleboxes to be glued on. Helmut has arranged a very ingenious way to ensure that they are located accurately, but I felt that they didn't achieve the look I was after, so they were left off pending a decision about what I would use -- never put off till tomorrow what you can put off to the day after.

An assembled skip frame in the high-tech jig:

Image
Bill

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Too soon old, too late smart.

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Postby Bilco » Sat May 10, 2008 4:12 pm

I now had three basic frames, but still no idea of how to arrange the supports for the skips. I found the section on the "Chagrin Mines" web site showing the Jeff Saxton supports, but Jeff doesn't appear to be making them any more. Several people have made perfectly good v-tippers using the Gnomy mounts unclipped from the chassis.

However, I wanted to have open space between the sides of the skip frame rather than a full floor. I bought some U-channel plastic section with a vague idea of bending up some inverted U-shaped supports as used on Georg Futter skips, but the idea remained vague.

Inspiration came when I found Alexander Lösch's Huber Paper Mill web site. The pictures:

http://www.frankenmodell.de/gn15okt06.html

Show that he used Gnomy supports, but altered the appearance of them. I realized that I could do something with them too -- a frantic search in the waste bin showed that I hadn't thrown them away yet. I took as my exemplar the Hudson skip chassis in 16mm scale by Colin Binnie. Out came the razor saw and the vertical sections of the Gnomy mounts were removed from the base -- a vertical cut down the inside surface kept the full height, which was then reduced by cutting the top portion off with a horizontal cut just under the pivot hole. The bottom edge was slotted to fit inside the skip chassis and over the central fore and aft rib.

Following the Hudson pattern I fixed pieces of L-section plastic strip across the skip frame, using the grooves provided by Helmut for his supports as a positioning guide. I also cut out the transverse rib and replaced it with some of that U-section I wasn't going to use for the supports. The remains of the Gnomy mounts had pieces of the L-section glued to the top edge, again following the Hudson pattern, with small slices of L-section at the outer ends -- I made a small jig to try to keep everything level and square.

The jig for the mounts:

Image

The mounts were then glued into position. To simulate the triangular shapes of the Hudson supports I made bases of thin plasticard which were fixed on top of the rounded frame ends, and triangular fillets were then glued onto the outer faces of the vestigial Gnomy mounts. I like to think that the final appearance resembles something a Hudson apprentice might have knocked up from bits from the scrap heap. The Hudson Rugga had its U-channel on the inside, of course.

A mount in the jig being assembled, and the parts to complete the mount:

Image

L-R: A frame made as designed, the frame modified, and frame with mount complete:

Image

The 3 completed frames - all I need now are axleboxes and skips!

Image

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Postby Bilco » Sat May 10, 2008 7:37 pm

Now it was time to think about cobbling up some way of fixing the wheels to the frame. Helmut's wheel sets have extended axles to fit in holes in his axleboxes -- but as I didn't want to use the axleboxes I would need new wheels.

I discovered in the back of the scrap box a length of 5mm square plastic rod with a round hole down the centre. I don't know where I got it from, or why I got it, but I thought I could make some reasonably Hudson-like axleboxes with it. The edges of one side of a 65mm length of this rod were rounded off, and it was then glued down the centreline of a similar length of 10cm wide 40 thou plasticard. When thoroughly dry this was cut into 4mm long sections -- voila -- Hudson axleboxes.

I found a packet of pin-point axle bearings made from some kind of low-friction plastic -- PTFE? -- in the back of a drawer of bits, which were a force-fit into the hole in the rod, and bought some Hornby 12mm, 3-hole disc wheelsets with pin-point axles. Apart from needing three hands to assemble the wheels and axleboxes, all went well.

Axleboxes well on the way. Top right the original plastic rod, bottom right two axleboxes, with the bearing visible, bottom left a line of fresh-cut axleboxes, and top left two axleboxes fixed to a frame:

Image

A rolling frame achieved:

Image

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Postby Bilco » Tue Jun 03, 2008 6:55 pm

Having got the skip frames sorted it was time to root out those Gnomy skip bodies and do something with them. I decided to erase all the surface detail and the pivots on the ends. The pivots were sawn off and the stumps sanded off; the thickened rim on the sides was sawn off too, and the sides rubbed vigorously on a large sheet of sandpaper taped to the workbench to remove the rest of the raised detail.

Once the skip bodies were smooth the new detail went on. I glued 3mm plasticard strip around the rim of the sides and ends, and added little L-shaped reinforcing pieces on the corners. Pieces of 3mm L-section plastic strip were then glued along the sides some 5mm below the rim to represent the reinforcement that most types of skip had in one form or another (an example of which I had just sanded off).

Two views of skip bodies: l-r as bought, detail sanded off, and detail added:

Image

Image

The next step was to make the pivots for the tipping action. As I had made the top of the mounts in the style of the Rugga skip I had to shape the pivots accordingly. I took 3mm slices of 3mm plastic tube and glued them to 3mm strips of thin plasticard -- in an attempt to get six with vaguely the same spacing I made a little jig to space the tubes 7mm apart. Another jig was made to assist in gluing the results onto the ends of the skip at a standard height -- about 9mm above the bottom.

Jig to get the pivots spaced semi-accurately:

Image

Jig to get the pivots fixed to the bodies at a standard height:

Image

The skip bodies now tipped as required, but the mechanics of the movement around the pivot now reared their head. In the prototype, when the body tips from the horizontal to the vertical, the pivot on that side rotates a quarter of a turn, so the point of contact when the body is horizontal must be a quarter of the circumference of the pivot from the stop. In the model case, with a 3mm diameter tube pivot, this should be about 2.3mm, but I had allowed rather less than that, so the pivot rubs against the end stop -- not a problem, given the lightness of the model and its low friction, compared with the prototype.

However, when the body returns to the horizontal the pivot rolls the full 2.3mm, and that puts the body off-centre on the mount -- indeed, if I had allowed a bit less distance it would put the opposite pivot outside the end stop. In order to keep the body centered when returning to the horizontal I therefore glued two Cambrian Models rivets (which are quite large) to the mounts inside the two pivots -- when the pivot rolls back to the horizontal it reaches the rivet and goes no further, rotating against it until the body reaches the horizontal. Sounds complicated, works a treat, and isn't very noticeable.

Skip frames with body horizontal and tipped to the vertical. The locating rivets can be seen when the body is tipped:

Image

The other fitting I put on the skip bodies was a pair of brackets at one end to hold a tipping arm -- when I get round to building the layout these are supposed to run on I want to have automatic tipping by a sloping bar at the side of the track, and automatic return to the horizontal by a wire overhead, and the arm can be fitted to tip on either side. As I will have to adjust the length of the arm by experiment, this method of fixing allows different length arms to be tried.

To make the skip frames look as if they are fixed together by something other prototypical than Plastic Weld I glued tiny slices of 1mm hex plastic rod in strategic places -- what seemed like hundreds of them, although the maths indicates that it was only about 120. I also substituted 10.5mm disc wheelsets (Bemo, I think) for the 12mm Hornby ones I bought to replace Helmut's, so that the frames now sit at the same height as Sidelines underframes.

All in all, the resultant skips look quite reasonable, and a bit different from what I started out with. Was all the work worth it? I suppose I could have had something very similar by buying the Slaters skips, and the cost would have been much the same -- ah, but the sense of achievement! Now what will Helmut think when I show him what I've done to his beautiful frames?

Now all I have to do is paint them -- you know my methods, Watson.

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Postby Glen A » Wed Jun 04, 2008 10:24 pm

Hi Bill,

You have gone to a lot of effort. I am interested to see the tipping arm. The challenge with getting all this to work automatically is:

1. To get the tub to tip with out lifting the chassis off the track. As your chassis' are plastic there is not a lot of weight to keep them on the track.

2. For the tub to then drop back down under its own weight. Seeing that tub balanced in the full tip position in the last photo means it will not return by itself (unless I misread your notes).

With my initial investigations and tests with theses tubs, I looked at putting an internal plastic false bottom into them to change the internal slope of the tub. So the loads started falling sooner, and you did not need to tip them so far up to fully empty them. By adding a small weight under the false bottom they also returned to normal position on their own.

You may want to do a few trial dump loads (if you haven't already) to make sure you are happy with now they work before you paint them.
Dumping them with your hand is easy. Using a push rod or other method can be a lot harder. Anyway, good work.

Glen

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Postby Bilco » Thu Jun 05, 2008 1:08 pm

Hi Glen, many thanks for your input. As you see from the pics, I have already given the skips an undercoat!

The first pic shows the tipping arm in place in the brackets at the end of the skip body -- well over the length I expect to use.

Image

I expect to have to reduce the friction between the arm and the tipping ramp, and between the pivot and the mounting, to reduce the forces trying to move the thing sideways -- also to have a check rail on the ramp side to try to keep the wheels running straight.

As you say, when the body is vertical it is balanced and will require a force to return it to the horizontal. I envisage a wire overhead, running diagonally at a shallow angle across the track. The arm will be moved in the right direction until gravity takes over. Of course, the height will require some tuning so as to clear the driver's head -- all good fun to come!

The chassis has that brass strip built in to the central rib, and I will put some lead shot under the end plating to increase the weight.

The second pic shows the 3 skips and a loco -- proof of progress at last:

Image

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Postby Bilco » Thu Aug 20, 2009 7:39 pm

When I bought those three Gnomy skips last year I already had one, but I had thrown the frame away before starting the 'Skips the Hard Way' project, so had a spare body knocking about. I've needed some relaxation this last week, and thought I would use that body to make another skip wagon -- but that meant that I had to make another frame.

I took inspiration from the skip that is shown with the Moseley Railway Trust "Red Dwarf" -- with inside axleboxes.

Image

The basic frame is four bits of U-section Plastruct, with a little mid-section stiffener. I couldn't make the uprights of the same stuff, as per the prototype, as the frame is narrower. I made up some simple uprights from plasticard and stuck a thicker piece at the ends to make a rudimentary 'buffer'.

The axleboxes are from some built-up section I made on the original build -- meant to hold the tipping arm. The tube is just the right internal diameter to take the standard steel axles.

Image

The skip body was scrubbed of detail as before, and I had made enough components for the previous build to fit it out as required. I've even added the new-form tipping arm:

Image

All that remains to do (!) is to scatter with liberal amounts of rivets from hexagonal rod, plus a few other details, and prep the wheelsets -- grind off the pin-point ends, remove one wheel and fit after painting. I'll use a bigger diameter wheel than the other three as the axleboxes are smaller, to get the frame heights to match.

Then all it will need is some paint, and I'll have something a bit different!
Last edited by Bilco on Fri Aug 21, 2009 12:38 pm, edited 1 time in total.

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Bilco
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Postby Bilco » Mon Aug 31, 2009 6:41 pm

Well, the new skip is finished and painted:

Image

Despite the bigger wheels it's not quite at the same height as the original hard-way skip, but unless I can summon up the courage to prise the axleboxes off and stick a piece of plasticard between them and the frame, that's how it'll stay.

The tipping mechanism works even better than the originals, and no tendency to fall over sideways, although I haven't tried it loaded yet. Still, overall it's worked out OK -- I think.
Bill

If at first you don't succeed, cheat.
Too soon old, too late smart.

https://sites.google.com/site/myoldlayouts/
https://www.flickr.com/photos/149926300@N07/albums

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Bilco
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Re: (F) Skips the Hard Way

Postby Bilco » Mon Oct 23, 2017 5:53 pm

A Flickr album of my labour-intensive tipping skips and easy tubs ...

https://flic.kr/s/aHsm7oZ3cf
Bill

If at first you don't succeed, cheat.
Too soon old, too late smart.

https://sites.google.com/site/myoldlayouts/
https://www.flickr.com/photos/149926300@N07/albums

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Re: (F) Skips the Hard Way

Postby PeterH » Tue Oct 24, 2017 9:06 am

Hi Bill, many thanks for putting together those Flickr albums. It’s great that those threads will stay useful.
Peter

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Re: (F) Skips the Hard Way

Postby southpier » Sat Oct 28, 2017 9:01 am

ditto; very impressive

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Re: (F) Skips the Hard Way

Postby docnjoj » Sat Oct 28, 2017 10:58 am

What they said! Thanks!
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