Tubular Rivets- how are these installed

Was passing by our store today and fished out a couple of the beastly things!…As used on Hurricanes etc.

Excellent, thanks for the photo of the offenders.

Regards,

Was passing by our store today and fished out a couple of the beastly things!…As used on Hurricanes etc.

We have had the experience of reassembling the engine thrust frame for 5447 for the past month. Its not an easy task those “top hat” ferrules are a tight fit. As comented on earlier the structure is rigid without the bolts they just hold everything in place. The ferrules seem to be the critical pieces. I believe it was the hangar 11 site that indicated 30,000 hours to restore a Hurricane and 12,000 for a Spitfire, not sure how accurate that is.
Just a few shots Mike Henniger took of the work in progress, test fitting of the rebuilt centre spar should be shortly.

I think you are probably correct. The method of joing tube ends is far from an easy method from what I have seen of the diagrams. I hate to think how much work it involves to remove a damaged tube and replace it with a good one.

Having been intimately involved in the restoration of both types, I know which one I would go back to – and it isnt the Hurricane!

Could you elaborate on why you wouldn’t prefer to restore a Hurricane?

……. I think the term ‘Simplicity of repair’ would have been more apropriate……

I maybe agree with you. Probability wise structural damage should occur less often on the Hurricane because there is less structural surface area. Once structural damage has occurred, then it seems like it would be harder to repair on the Hurricane than equivalent damage on the Spitfire?

(Not to confuse “simplicity of repair” with “design robustness”, I think these are separate components of an aircrafts “serviceability”)

Yes I can certainly understand what you said there. I think the term ‘Simplicity of repair’ would have been more apropriate. The chances of a bullet hitting something structural in a Hurricane is far less than in something like a Spitfire or 109. Mind you sod’s law says that if you are hit it will be something vital. The example that would suitably demonstrate this is trying to flick a screwwed up bus ticket through a fire guard with a large sized mesh. 80% of your shots will hit the wires

Understanding how the designs were perceived in period is not really a case of which aircraft was the most complex. Its really to do with how familiar the construction method was to the designers and the people that put them together (plus those who would be tasked with repairing them) and how established the manufacturing facilties were to produce the aircraft at the time.

In the case of the Hurricane (which most certainly is highly structurally complex to our modern eyes) Hawker simply employed their tried, tested and familiar construction methods to produce it (its so similar to the earlier bi-planes you can hardly tell the difference between the Hurricane fuselage structure , sans wood and the bi-plane predecessors).

The Spitfire, on the other hand was at the time very challenging to set up for large scale manufacturing and thats where the ‘legend’ was born. Today we still hear of the Hurricanes ‘simple’ and rugged construction but today, side by side comparison with a Spitfire gives the opposite impression!

Having been intimately involved in the restoration of both types, I know which one I would go back to – and it isnt the Hurricane!

Bruce

Hi, if you want complicated just compare a Spitfire rudder or elevator with that from a ME 109. God, all those pieces !! what was Reg thinking about ?!!

Steve

My point exactly, by comparison the Hurricane was an exercise in simplicity

The tubular rivets were designed to be used in outposts of the empire where electricity for welding might not be available!

That would certainly make sense- all you need is the tube for the rivet and the mandrels and you are set (excuse the pun).

In terms of production methods the Hurricane has to be one of the least complicated build jobs in the British aircraft manufacturing industry of the time

An interesting question.
Currently it seems to be agreed that the Hurricane is quite difficult to restore compared to other aircraft. Yet when they were originally built I have read that it took less time to make them that the Spitfire.
To my eyes, which are used to modern construction methods, the Hurricane appears awfully complicated.
(I still find it hard to believe that it took less time to build a Hurricane than a Spitfire- wonder if this was actually proved or whether this is opinion that has become fact with the passage of time?).

In terms of production methods the Hurricane has to be one of the least complicated build jobs in the British aircraft manufacturing industry of the time

Hi, if you want complicated just compare a Spitfire rudder or elevator with that from a ME 109. God, all those pieces !! what was Reg thinking about ?!!

Steve

Maybe also an indication on how labor was comparatively inexpensive too? Either way I am sure the decision was perfectly logical at the time it was made- pity we will never know the full reasoning. That’s one of the things that intrigues me about the Hurricane- why was it so complicated!

Thanks for the insight on the shear forces on the joint.

Regards,

In terms of production methods the Hurricane has to be one of the least complicated build jobs in the British aircraft manufacturing industry of the time

The tubular rivets were designed to be used in outposts of the empire where electricity for welding might not be available!

I guess we must go back in time and ask Sydney Camm, I can but presume he was not keen on welding!

I guess done for weight saving purposes. The combination of ferrules, spacer and rivet, a touch lighter than a nut, bolt and washer!

Maybe also an indication on how labor was comparatively inexpensive too? Either way I am sure the decision was perfectly logical at the time it was made- pity we will never know the full reasoning. That’s one of the things that intrigues me about the Hurricane- why was it so complicated!

Thanks for the insight on the shear forces on the joint.

Regards,

[QUOTE=HurriRV7;1375820 Still seems like an awfully complicated way to make a joint especially when you could us a bolt.

I guess done for weight saving purposes. The combination of ferrules, spacer and rivet, a touch lighter than a nut, bolt and washer!

Chumpy.

The key part being the intereference fit top-hat ferrules, these normally made of S80 high tensile stainless steel. These take the shear loads on the joint, the tubular rivets really only provide a clamping effect, preventing the ferrules from moving.

Thank-you for the explanation, it had never occurred to me that the Top-Hat ferrules were for taking the shear loads. Makes perfect sense now.

Still seems like an awfully complicated way to make a joint especially when you could us a bolt.

Regards,

Photo of a typical Hawker fuselage joint, in this case on a Fury.

The key part being the intereference fit top-hat ferrules, these normally made of S80 high tensile stainless steel. These take the shear loads on the joint, the tubular rivets really only provide a clamping effect, preventing the ferrules from moving.

Whilst it might seem complicated, Hawkers used it to great success over many years and a wide variety of types.

Hope this explains things, Chumpy.

The attached sketch shows the basic principle of tubular rivets, quite simple really.
The rivets used by Hawkers normally had the head pre-formed, just the tail getting being ‘squeezed’ to finish the joint.
Once you are ‘tooled up’ a very quick and effeicent method of construction pioneered on the 1930s biplanes (Hart, Demon etc). The rivets came in steel and light-alloy the lattter requiring to be heat-treated prior to installation.

Somewhere I have photos of actual Hawker joints will try and dig em out later.

Chumpy.

The first thing that springs to my mind are Chobert rivets.

http://www.hansonrivet.com/w52.htm

http://www.bayrivet.com/chobert_rivets.htm