BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

I was tempted to assume they had thought of that but I am still not clear on whether the "fitting" is needed due to variations in the size of the reamed holes due to insufficient accuracy in the reaming process, arising perhaps from insufficient rigidity in the drill or drilling set-up, or perhaps changes in diameter due to wear of the reamer.

 

Your getting into an area which is not my speciality but I do know that reamer wear has been discussed. If you are coming to the AGM, Geoff will be back from his holidays and will be able to answer your questions

 

Has there been any consultation with the A1 Steam Trust?

 

Dunno, saw Mr Elliot on Saturday so should have asked him really.

 

Can one park at CTL Seal?

 

Yes, no problem but not until after 1230 when the Saturday morning shift have emptied the car park. Go through the gate and look for the car park on the left. The car park is in the box. The way into the assembly shop is by the arrow

 

Given the quality of the finish on those bolts and their conformance to size, I would query why not ream the holes to the correct size for the bolts?

Seems like additional rework to machine down the bolts more, not to mention it will be a challenge to get them as neat as that on a manual lathe again.

 

Kinda like I said 28 posts ago!
Ray.

 

I think it's best if Geoff responds to this debate at the AGM on Saturday. He is on holiday at the moment and is back tomorrow - setting up at CTL Seal. I've advised him of this debate and he will be prepared for your questions

 

Thanks.

 

Didn't see you're post I'm afraid. I did think about not saying anything but decided on balance that it may help. Glad someone else sees it the same as me at least.

 

Two posts after I raised the same point in fact.

 

Can I just say I thought of it (*) even earlier but didn’t write it down

(*) whatever the “it” is that we are talking about ...

Tom

 

I didn't, and im sure there are good reasons for not welding everything but if anyone wants to remind me...

 

This is getting outside my field of expertise, which is pretty narrow in the first place, but it is a brave step to replace riveting with nuts and bolts. I can readily appreciate the principle of using a fitted bolt to ensure continuing alignment and no relative movement of components but I have a niggle about being able to sufficiently tighten the bolt. In bolt theory, it is usual to tighten a bolt to a level where it is not subject to stress variation, which effectively requires the bolt to be stretched. With an interference fit that will be difficult to achieve because of that very interference. This might lead to the bolts failing in fatigue., depending upon how they are loaded. If it is a pure shear force, it will probably be OK but if it is a tensile force then it may prove troublesome I don't know whether I'm totally off the mark with this thought.
Rivets have been the norm for 150 years. for these joints. Change can be good but it is a brave person that tries it for the first time. A steam loco frame is pretty dynamic and subject to all sorts of stresses. Good luck and I hope it works.
Another thought/question; were Huck bolts ever considered?

 

My own idea would have been to ream the hole to a size to suit the bolt, so I raised a query with one of the foremen at Bridgnorth yesterday and was surprised to learn that they too ream the hole to a known size and then machine the bolt shank to the correct fit. So that shuts me up. anyway!

One of the advantages I've always understood about riveting is that the compressive forces needed to turn the head also expanded the shank to completely fill the hole, removing any clearance between hole and rivet. This is why rivets must be driven out after the head is ground off.

 

I just wonder why the decision was made to change to bolts? As far as I am aware the A1, P2 B17 Patriot, 4709, Saint, County, G5 etc are all sticking with traditional riveting. Wouldn't a change like this mean more paperwork and an approval process from the VAB? The question is, why do it for no discernible benefit?

Keith

 

Please see post https://www.national-preservation.c...-discussion-thread.21515/page-76#post-2524567

 

I was wondering what the SVR did as there is a photo of a new drag box for 4930 in the latest News. When you say they machine the shank to fit, is this done based on measurement of the diameter of individual holes, or to a pre-determined diameter based on the use of say a 1" or whatever (non-adjustable) reamer. Do they use a floating reamer holder?

Rivets do seem to work loose based on reading description of loco overhauls, although I guess one takes a view as to the working life. I wonder if one could use a combination of fitted bolts, acting as precision dowels to locate the plates/stretchers, and high strength friction grip bolts, which although a rattling fit, would provide a clamping force (and sheer-resistant strength through friction)?

 

Apparently, they match all the holes and fitted bolts individually.