Loco mounting jig

[Garry ColesParticipant @garrycoles69390]

Hello everyone.

I’m currently building Doug Hewsons BR Std Class 4  2-6-4 Tank loco in 5 in gauge.

I’ve got the whole chassis mounted at each end on the buffer beams centrally through the draw hook holes with 5 mm bolts and with spigots going into the buffer mounting recess’s also using 5 mm bolts. The whole loco is then supported by a swivelling rig so that I can work on the top and the bottom just by turning it over. My question is, do you think those mounting bolts will be strong enough (in shear) to take the weight as I’m constructing it. Or do I need to add some extra mounting fixtures. The finished boiler alone weighs 40lbs.

I don’t seem to be able to find the weight of the finished model on the internet.

Any suggestons please.

Garry in sunny Jersey

[RolsterParticipant @rolster]

Hi Garry

Looks to be a lovely build and the idea of the jig is Nice.

My personal thought on the 5mm bolts are that if full thread type they will be two small with just one at each end of the Loco. If set bolts of a known high quality with the rotating part of the jig being on the solid part of the shank, they might last.

Perhaps to hold the buffer beams to a cross bar through the draw hook holes and the buffer holes themselves, if going for the aft retained design, with three 5mm bolts at each end would be fine and then the cross bar to frame with a 10mm bolt or rod would be adequate.

When dealing with this type of jig in the past the pitfalls seen are, as you build the engine up the upper body weight is significantly higher than the lower frame weight beneath the buffer beam height so allow for some vertical adjustment of the swivel points as otherwise turning the model over once you put the boiler in place will be difficult.

BR Roland

[BazyleParticipant @bazyle]

A typical 060 is about 120lbs so make a guess on the extra length factor.
Re top heavy: biggest danger might be the day you try a small position adjustment and it decides to flip over until stopped by the chimney.

[noel shelleyParticipant @noelshelley55608]

The bolts are NO WHERE near thick enough ! I would aim to mount it on the buffer stocks ! Then your mounting bar onto a bearing or plummer block bearing at one end and a worm and wheel at the other so you can turn it to any angle and it will stay there with out the top heavy issue being a problem ! Noel.

[Norman Lorton 1Participant @normanlorton1]

 

The problem is going to come when you add the boiler and the CofG of the swivel point needs raising. It will need plates on the ends of the frames at a new distance away from the buffer height datum. So you will have to raise and lower the loco with some other support and jacking system. Also, when you are finished what will be around 100kg needs to be removed from the frame and easily placed on a trolley with rails. 100kg is a four person lift without mechanical assistance.

I built a wheeled trolley, with rails on top, then strong vertical supports that bolt to the trolley frame with vertical screws (like a lathe feed screw) to raise or lower a block at each end. Each block has a large pin about which a friction clamp can rotate. Affixed to the clamp are plates to allow CofG adjustment. One of the plates grips firmly to the end of the loco frames. The decorative buffer beams can be left off until the loco is in its final build stages.

The photo shows my assembly supporting a 45kg 0-6-0 with wooden clamps around the buffer stocks. More recently the same frames, with adjusted CofG have supported a 100kg Britannia but with steel clamps around the frame ends. With the CofG adjusted to within a few mm the loco can be turned by hand.

I only post this in case it helps you plan ahead.

Norm

 

 

[duncan webster 1Participant @duncanwebster1]

I do wish people would do some simple sums before pronouncing. A grade 4.6 bolt has a yield stress of 240 MN/m^2, so an acceptable shear stress of 89MN/m^2. It has an area of 19.6 sq.mm, so an acceptable shear load of 1744 N, which is 392 lbf. The OP has 2 of these each end.

I have a piece of unistrut supported from the rafters. Using this in combination with the scissor lift trolley gets away from difficulty of lifting loco onto rotating stand. I found having the pivot a bit above the buffer beam made the whole thing balance with the boiler on.

[noel shelleyParticipant @noelshelley55608]

Sorry Duncan ! But I would not be happy with my loco hanging on 4 5mm bolts ! Noel

[duncan webster 1Participant @duncanwebster1]

Well my 250 kg chain block, which is fully certified commercial job, has one off 5mm bolt in double shear holding the hook on. I daresay it’s a bit better than a grade 4.6, but is is not marked. Not many 5″g locos weigh anything like 250 kg.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, my two 500 Kg chain blocks have a 6mm bolt holding the hook to the chain, and have both had close to the 500 Kg on them, the older one having had that many more times than the other one.

Regards Nick.

[Garry ColesParticipant @garrycoles69390]

Thanks everone for all yoir comments. It gives me a few things to think about.

Garry

[Howard LewisParticipant @howardlewis46836]

Being an adgerent of the Victorian “Brick mausoleum” school of engineering, I would feel happier with two 8mm bolts at each end.

If the supports are too strong, no problem, but the converse means danger and trouble.

Again, with safety in mind, with the loco becoming more and more out of balance as build proceeds, I would advocate rotating by means of a single start worm and wormwheel.  That way, even off balance, the single start worm will prevent the loco rotating out of control.

Howard

[BazyleParticipant @bazyle]

Norm – your solution is interesting. Next time it is not busy holding a loco please take some more photos from other angles.

[norm nortonParticipant @normnorton75434]

OK, as requested, but this is a bit beyond what the OP was looking for.

The uprights are steel box section with a milled out slot in one side. Welded cross member at the bottom and bolt on stretcher at the top to allow assembly. The central steel carrier runs vertically in those slots and takes any side or twist thrust to keep the screw thread unloaded. A welded pin in that carrier has a split aluminium clamp gripping it. The screws allow grip adjustment. The drilled steel plate allows height adjustment to enable loco rotation along (near to) its CofG. It is important that the mounting to the loco is rigid and does not impose any downward twist. The towers could be half the height shown and would still allow full rotation.

One photo shows a mounting clamp that is attached to the loco front frame stretcher with buffer beam and stocks removed. The other shows a long steel tongue that goes into the rear loco drag box.

Hope these are of some interest.

 

 

 

 

 

 

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