Landships II

EDUARDO MAMORETTI · General

FT 17 RIVETS

LincolnTanker · Commander in Chief

Hi Eduardo,

I've looked at my photos of FT-17s, including the Armour Photography 15 book, and all the main constuctional rivets on the hull�seem to be�conical. But rivets holding parts, ie.�the ring under the turret,�to the hull are mostly�rounded.� Some look quite flat. The track gear looks to have only rounded rivets.

The final shape of a rivet head is formed by the 'snap'. It looks to me that Renault used an increased angle�drill to form their snaps, It would be possible to form molds for making your own rivets.� I have seen conical rivets on British tanks,�I suspect they may have been fitted during a 'field repair'.
�
I've attached a video to show riveting in action for anyone who hasn't seen it.�

http://www.youtube.com/watch?v=VAArP6swIuY

Hope this is of some help

EDUARDO MAMORETTI · General

Very Kind comrade,
Thank you for illustrating me. Indeed even german ww2 tanks have had conical rivets, from various sizes, also italian and some structural�in japanese CHI-HA even.
Higly appreciated!
Ed smile

kieffer · Commander in Chief

Hi all,

as far as I know, conical rivets are just another type, and have nothing to do with ballistics. They were mainly used in the ship building industry. They were easier to handle especially in cramped places and angles, and quicker to work with. The conical head is the fixed head, the other end is formed by the snap. For round headed rivets one needs a special formed tool, the dolly who keeps the rivet in place. It is physical very hard labour and one can not keep the dolly exactly on the right spot for long.
The only explanation I can think of, why the conical head is outside is this. First, to put the conical side inside a cramped interior (certainly in this very small Renault) would be a danger for the personnel. Second, the snapper has the snaphammer who does the work, but the guy who holds the rivet in place, the dollyman, needs to stand firm.Therefore he needs some room to stand, which you don't have inside the small compartment.

Kieffer

LincolnTanker · Commander in Chief

Has anyone any photos of the FT-17 being built?� I would have thought the sides would have been revitted together first and then they would have been rivetted to a complete base. Maybe they were built sat on their rears.

Some times the hammers were fixed to a frame like a g-clamp with the dolly fixed opposite, so a dollyman wasn't holding the dolly, he guided the frame.

I do think they were to help deflect direct hits on the rivet, see drawing. The fear of a rivet being burst out and rattling around the inside of such a small hull must have been great. It may have only been as effective as having a rabbits foot with the crew but it may have given similar comfort.

(For those who are not familiar with the rabbits foot, it is looked on as a lucky charm in some areas of this planet.� But as people point out, all 4 weren't very lucky for the rabbit.)

EDUARDO MAMORETTI · General

kieffer� & LincolnTanker ,
interesting points! I am grateful to you all

kieffer · Commander in Chief

Hi Lincoln!

you are right with the clamp. What still puzzles me is that these conehead rivets look a bit "funny". It looks sometimes if there's a centre pin, others seem to have a base like a nut.
You might even get the impression that they are deformed bolts or nuts, rammed for ever on their places.
Cone heads are, at least the ones I know of, not fully coned, they have a small flat top, which I don't see on the Renault.
So I might be very well wrong, as far as the use of them in the Renaults and others. (pictures of Cromwells show rather big coneheads, there too I can't really figure out how they were made).
The deflection, I have my doubts. Especially these first tanks had almost nothing in their concept to deflect bullets. They relied more on the armour thickness, for the rest it was one shot trap after the other.
The rabbit foot, I know...would be an interesting topic: superstition at the front line..

Kieffer

EDUARDO MAMORETTI · General

At least fro WW2 german tanks, one tends to see conical head bolts on the less ballistic surfaces, ie. the almost vertical sides of the jagdpanzer Elephant.
As� a private conclusion, in that case they tried to compensate a weak part of the structure as a rivet�attached to�a non ballistic plate by�improving the head shape perfomance.-
I dont, nevertheless, asume this is the only explanation. But one have to take into consideration that the rivets�easily�turn into shrapnel inside a vehicule when it recieves a hit...with �fatal consecuences for the crew...
This, among other reasons as mass production necesities and the update of the constructive techniques lead� WW2 tank designers to gradually adopt welding techniques...
Ed smile

CharlieC · Legend

As far as I'm aware the problem of rivets shearing off and turning into projectiles wasn't an issue until the the thickness/quality of armour plate was sufficient to stop small arms rounds reliably. This didn't happen until the 1930s. The Russians switched their T-26s to all-welded hulls after experience in the Spanish Civil War. Most Russian tanks were all welded by the end of the 1930s - this wasn't so for British or Japanese tanks. There were also improvements in welding technology that made welding competitive with riveting by the 1930s. A lot of advanced welding technology originated in Russia which may account for the early adoption of welded hulls.

The comments about the Cromwell and Elefant are somewhat of a distraction. The Cromwell conical nuts were fasteners for applique armour on the turret - they were factory installed. The Elefant/Ferdinand hull was a recycled Porsche Tiger hull - the casement sides were simply bolted onto the sides of the tank hull using shaped nuts rather similar to the Cromwell system. The original Porsche Tiger hull was all-welded.

Regards,

Charlie

-- Edited by CharlieC on Friday 8th of January 2010 04:15:29 AM

kieffer · Commander in Chief

Hi CharlieC,

thanks for the explanation! As far as the Cromwell, Ferdinand and others concerning, the puzzle is solved. I took a better look at some pictures and now I see. I think that there was a combination of welding and bolting?
Then, I took another look at Ft17 pictures...now I get the uncanny feeling that the assumed coneheads are no rivets at all, but also bolts. On photo's ( I will try to post them later) of the opened hatch above the engine, you can see clearly normal bolts, the outside have conical forms. Pictures of the front, I see nut squares, centre pins.
If that's the case, then I see the deflection story a bit different than I did.
The only way to really find out� is a visit to the museum. I am planning Brussels in the spring.

regards, Kieffer

LincolnTanker · Commander in Chief

Hi all, I've attached a photo from the Armor PhotoGallery #15 showing the Brussels FT. Flats can clearly be seen on the rivets/bolts, if they are bolts why aren't they normal hex?

CharlieC · Legend

kieffer wrote:

Hi CharlieC,

thanks for the explanation! As far as the Cromwell, Ferdinand and others concerning, the puzzle is solved. I took a better look at some pictures and now I see. I think that there was a combination of welding and bolting?

(snip)
regards, Kieffer

Bolting and welding thick armour plate was a technique used by the Russians in early WW2 tanks. The KV tanks had their thick armour plates joined by this technique. It was an expensive way to join plates and was used mostly by the Kirov(Leningrad) factory.
You can see this clearly in KV-2 turrets - there are a row of dimples along the join lines of the armour plates where the boltheads were cut off after welding (www.jagdtiger.de). Interestingly the T-34s used welding only - the Kharkov factory used advanced welding techniques developed by the Paton Institute in Kiev.

I think the welds on the edges of the bolted plates on the Cromwell/Elefant were mostly to seal the joint and limit the amount of buckling that would occur if the plate edge was free.

Regards,

Charlie

�

-- Edited by CharlieC on Saturday 9th of January 2010 05:39:02 AM

kieffer · Commander in Chief

Hi Lincoln,

a good question. I can only guess now. Some look as if they have only two sides, one looks hexed, others look like rivets. A picture from the inside would be helpfull.
Do you have one of the engine cover, closed? The hinges are certainly bolted, with normal hexe flat bolts inside.

Kieffer

LincolnTanker · Commander in Chief

Hi,� Oscar Zulu has posted a link to some v. good Aberdeen photos. I've attached a couple. I does look bolted. The next question is were they coach bolts?

-- Edited by LincolnTanker on Saturday 9th of January 2010 12:39:40 PM

kieffer · Commander in Chief

Hi Lincoln,
Which type of coach bolt do you mean?

Kieffer

LincolnTanker · Commander in Chief

Hi Kieffer,� under the head a square�is�formed, this locates in a square hole.
This stops the bolt�revolving when the nut is tightened.�

-- Edited by LincolnTanker on Saturday 9th of January 2010 03:07:16 PM

Ironsides · Legend

Is it actually possible to drive square holes in armour plate and if so how?

Cheers smile

LincolnTanker · Commander in Chief

RE: FT 17 RIVETS and square holes

kieffer · Commander in Chief

RE: FT 17 RIVETS

profil · Corporal

Hi!

Bolts�not rivet.

http://www.com-central.net/index.php?name=Forums&file=viewtopic&t=5391&highlight=ft17

LincolnTanker · Commander in Chief

Hi Profil, now that's what I call clarification.� What brilliant photo's. anymore biggrin

.

Ironsides · Legend

Hi many of the "rivet" heads�would appear to have "Flats" on the rim of the Cone, this would enable you to get a spanner on it at least whilst the nut is tightened on the inside...�

http://www.landships.freeservers.com/jpegs_new/number_11/char_tsf_sau_eg%20(6).jpg

Cheers smile

kieffer · Commander in Chief

Hi all,

we're almost there then! The type of the bolt, well I guess that can only be clarified if we have a picture with a missing bolt. My intuition says that they simply used a ordinary type without squares. And that they are forced in without heating the plate. Renault and the four other companies were by that time already big manufacturers, with efficient production lines. That's why I can't just see a costly and time taking way of heating up plates (which destroys anyway the hardened structure), flame cutting squares or punching.
Saying this, I do not deny that it is technically possible. But forcing in a normal machine bolt in a slightly undersized hole would do the trick too.
As I mentioned before, some of the bolts seem to have even only two flats, for an early type spanner. I remember seeing that type (bolt and tool) before but I just don't know where.

Kieffer

Ironsides · Legend

Hi� Ive seen similar things before I dont think its that unusual, what threw me was more the conical heads its clear now that they are a nut and bolt arrangement...
I might suggest though that some are not original, possibly modifications or repairs using whatever was available at the time, the inside looks like Mechano and those brackets holding everything together looks very iffy.... crude really, just bits of bent plate not even angle iron... but this very crudeness probarbly made it easier to assemble, I think anyone with a decent industrial metalwork shop could probarbly put one of these together...
The main strength of the hull�seems to be in the armour plate itself but I can see it having a lot of weakspots around the joins....
As for the holes in the plate there were techniques at the time for locally heating the area using an electric arc this was developed for putting holes in�warship armour since it was'nt possible to otherwise drill it....
Its possible it was all drilled and then hardened, but I dought it.. at least its seems the plates may have been rolled as part of the hardening process, but as I dont know what kind of armour was used its difficult to say...
The one thing I will say is�I dont think it was the same type�of steel armour as used by the british, you might notice that british tank armour�has an alarming tendency to crack up, I cant say Ive noticed the same thing�on Renault FTs.....

Cheers smile

CharlieC · Legend

I think the French were somewhat more advanced than the British in metallurgy in WW1. The French were making arc furnace steels long before the British adopted this practice. The advantage of arc furnace steels is that the composition can be controlled fairly precisely and it's possible to make steels economically with much higher proportions of alloying elements than steels made by Bessemer and similar processes. I have noticed that images of damaged St Chamond tanks seem to show that the armour tore rather than failed by brittle fracture - this might indicate a difference in the toughness of the armour plate used.

I'm still puzzled by the rows of bolts in the image based on the practice on later vehicles. Certainly the Russians used a practice in the 1920s and 30s where the armour was rivetted to a frame - the only use of bolts was where it was intended that an assembly could be removed for field maintenance - the T-28 is a good example of this.

Anyone know when homogeneous armour plate was first used on tanks? - that is plate which is not heat treated to produce a hard skin like naval armour.

Regards,

Charlie

kieffer · Commander in Chief

Hi all,

The main strength was in the plating, it did'nt have a proper chassis.
Bolting was practised for easy access afterwards; in difficult places; when plating was too thick and, that's probably the thing here: it depends on the forces on the construction. You can't rivet just everything. I mentioned the lack of a chassis, here it's merely a box fit together. Later Renaults like the 33 en 35 had serious trouble, with the body distorting after rough going. Rivets can snap off easier than bolts, they don't hold out any force. My English is not good enough to explain that properly, but I am not assuming this.

regards
Kieffer

Tanker · Field Marshal

Bonjour,

On�the French military film done at the end�of 1917 (or�perhaps begenning of 1918), during a visit in Billancour's factory, from Louis Renault and the American Armee Comitee, it's possible to see that all rivets of the Renault FT were rounded. (Film from Ecpa-D - Fort d'Ivry - All in Ecpa-D DVD)

I think that, all�modified rivets are post WW1.

About steel armor plate. Most of these plates (for Renault FT and even for some Schneider and Saint Chamond) were bought in Great Britain.

Michel

kieffer · Commander in Chief

Bonjour Michel!

you do mean rivets, not bolts?...
The ones on the Ft at the Overloon war museum (The Netherlands) have two straight edges at the base, other two are rounded. The top is more or less conical. (on the outside on the hull)

Regards, Kieffer

kieffer · Commander in Chief

Bonjour Michel,

forgot to tell that the same types are to be seen on wartime pictures, so in this case it is not a after war improvement or something the like

LincolnTanker · Commander in Chief

Hi Kieffer,

I would have thought that a riveted structure would be far tougher than a bolted consrtuction.� When a rivet is fitted it is squashed into the hole filling it up and as it cools the rivet shrinks, squeezing the plates together with a great deal of force.
The filling of the hole 'pins' the plates in place so the plates cannot shimmy about.

Bolts, unless of the fitted type�(ie. ground diameter in reamed hole), rely on friction to secure the plates.�Clearance between the hole and bolt allows movement.�I would have thought a bolted Tank running over rough surfaces would tend to loosen the bolts and cause distortion. Was part of the routine maintenance tightening the bolts?� Have you noticed how small the bolts are?

Hi Tanker, I was told that a lot of the steel used in the first British Tanks was German, stock piled before the war. The thicknesses were in millimeters.�Do you know more?

Tanker · Field Marshal

Bonjour,

On the film, it's just an exterior outside part or left side chassis.

I have found a good war photo of the number 67411 (a model with gun turret). It'is a Renault production model. The front chassis' rivets are conical.

I think the only good standard, for first war fabrication, is the number 66016 from Bovington museum.
This instruction model, giving in June 1917 to the British Army, is probably not modified. On this tank :
�� - the chassis' rivets are conical.
�� - the tail's rivets are rounded�(like on the Invalides' museum model)
�� - the track roller's carriage used rounded rivets.

On the different turret's models it's possible to see round and conical rivets from different size.��

On the Invalides' museum model, most of rivets are conical with the two straight edges at the base. These models are, perhaps, bolts using screw nuts on the other side.�With the edge on base, it's possible to used�wrench for disassembly steel plates.
I not found (fot instance) war photo with this kind of rivet (with edges), and I�have not dismounted�this tank to look inside�. . . . .

In Saumur's museum�modern bolts are used. These bolts are just modified, on outside of the vehicle, to look like original rivets.

Renault FT life is already very long and a lot of models were repaired and modified by many countries.

Vaste sujet . . . Michel

Tanker · Field Marshal

In the first Renault studies for the FT tank, the 16 mm steel plates tested were coming from the British Company Miris. (5� R�union du Comit� d'Artillerie Sp�ciale du 170222).

In each lots received in France, a steel plate were chosed to be tested with infantry shoots.

The most important thicknesses�used in French's tanks were (in millimeter) : 16 - 12 - 8 - 5,5.

Michel

-- Edited by Tanker on Tuesday 12th of January 2010 02:39:06 PM

kieffer · Commander in Chief

Hi Lincoln,

you're absolutely right, but there's one exception. As you mentioned the friction: that's a force between to riveted plates up and down.( I am getting a bit hopeless not to know enough technical English). Another force occurs when riveted angles are bent, in other words the angle between two plates changes. Translated literally from my language its called "rivets under pull". The two heads of the rivet are then pulled away from each other and can snap.Therefore: bolting. The other reasons I mentioned, room, access etc.
By the way: you're right too about the "filling" of the hole by the "growing" shaft of the rivet. It's also a risk. Too close on the edge of a plate and the hole will rip.
Same for the distance between rivets, we call that stitch, in English pitch?
For bolting without movement: holes slightly undersized, then almost exact with a how do you call that...not a drill but a kind of rimmed needle, then the bolt forced in.
So far the theory. It's still possible that bolting was chosen for economical or efficiency reasons. If for instance the plate work was done elsewhere and the assembling let's say by renault, well it was a car plant and may be not equipped with tools and labourers you find in heavy steel manufacturing?

Regards
Kieffer

kieffer · Commander in Chief

Bonjour Michel!

There is at least one photo of an Ft, showing an American crew, in wartime France.
The bolts look quite battered, but recognisable. It's the two side straight type.
But also conical with sharp points. some seem to have a nut base.
I will try to post it but therefore I need assistance, I am not that handy with computers.
The Overloon (I think it's on their website): mainly the same type. Therefore I don 't think it's a make over. It's a Beutepanzer. But even the Germans prepared many Ft's to be fit for fighting, so who knows what they altered. Or they took the turret and placed them on concrete strongpoints called Tobruk. They did that (R35 were used too I think) at least in the northern piece of the wall but may be in France too?

Salut!
Kieffer