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It's just a pic that I have keeped form somewhere for reference to pinning the stemOriginally Posted by bozzer
Come on Barry ... Duff info.
So there's a hole in the piston body and if you look close it looks like a hole in the inside of the piston head where the rod goes in ... so back to a pin. Are they all like that or is that one that someone has DIY fitted a pin into?
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There is a cross pin through the piston head on these. I did not think that there was on the more recent Diana model pistons.Just got a 1968 Diana 35 yesterday and piston rod came loose with seal screw broken
I haven't had a proper look yet
Not sure if the pin has sheared on Bruno's as well as the screw attaching the seal assembly but these are replaceable parts. Only trouble will be if there is any major damage of the piston, rod or scoring on the cylinder.
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2nd and 3rd pic in here indicate something completely different and even more disturbingA few more pics to look at
THAT PISTON ROD LOOKS TO HAVE SHEARED
No groove at at all on that so the front part of that rod will still be in the piston
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Cheers.It's just a pic that I have keeped form somewhere for reference to pinning the stem
So I'm thinking that is an aftermarket home made pinning.
It also proves that the guy you mentioned in the original post is wrong. Those crimp marks do line up perfectly with the groove in the rod nose. So I'm even more so going with the crimping holds the lot together at the factory.
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Cheers. Totally missed the 280 category
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The vid in the initial link showed a piston rod with a groove detached from the piston.
The next series of pics I've quoted in the post above a minute or so away show a totally broken rod
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when I used to fit heads and rods into piston bodies . the body was placed in a two piece die . the die had 2 cut outs in it, you placed swage blocks into these slots then pressed them in. as nick-g said it would press the body out of round but the dies stopped this (if more than two swages was needed you just altered the piston body in the dies) as for it not pressing the swage into the slot, if in a die the excess metal has to travel somewhere and the groove if not true in line with the piston head groove it will travel down to the rod groove. how far depended on the hardness/thickness of the piston body metal. the piston head and rod was always harder than the body to help the swage process. if no dies are used then looking at different pistons in the higher end brands the piston head and skirt are nearly always bigger than the piston body to compensate for slightly out of round bodies..
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I bet you a bacon roll it's a crosspin, Col.
That video from Barry's previous thread, where the guy is trying to work out why his gun won't cock, while he casually pulls out the piston rod to examine it? That's just plain odd.
Somebody needs to get a Diana piston X-ray'd
Last edited by Rickenbacker; 12-01-2018 at 02:18 PM. Reason: grammar
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Either the importer or Diana really need to comment on this.I bet you bacon roll it's a crosspin, Col.
That video from Barry's previous thread, where the guy is trying to work out why his gun won't cock, while he casually pulls out the piston rod to examine it? That's just plain odd.
Somebody needs to get a Diana piston X-ray'd
Likely to go viral and flatten sales.
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Even a stopped clock is right twice a day
For legal reasons I doubt they would comment publicly. Looking at some serious liability issues here.
Good deals with these members
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LOL Diana was shocked in 2012
http://www.network54.com/Forum/18447...age/1334117229
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Just read that whole thread on N54 that you've been contributing to Barry. Read right up to yesterdays date.
I accept the feeling that the crimp may be the only thing holding everything together but do wonder whether that crimp would be able to exert enough force to distort the solid head enough to make a hold on the piston rod groove. Reasonable thought on my part suggests not and a pin would be needed. Relying on a distortion of the solid head to hold the rod would be sketchy at best and massively negligible at worst.
The thought of a loaded rifle having an unintentional discharge due to a rod detatching doesnt bear thinking about.
The thought of wobbly piston rods being common is more than enough to get my bum a little twitchy with worry.
I may have to resort back to my thought of a pin holding the rod to the head before being crimped in the piston body (surely ?)
Guess until a bandsaw if fired up, we'll never know
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I think what you see down the piston is whats left of the rod, showing what looks like a fracture in the pic.2nd and 3rd pic in here indicate something completely different and even more disturbing
THAT PISTON ROD LOOKS TO HAVE SHEARED
No groove at at all on that so the front part of that rod will still be in the piston
The rod could be crimped in the nose prior to fitting in the piston as well as friction & shrink fit.
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We'll have to wait 'til the end of this diet.I bet you a bacon roll it's a crosspin, Col.
I started off in the pin gang. Like I said earlier Phil, it just doesn't make sense that Diana would machine the groove, then drill/mill the hole in the head to put the pin through to retain the rod, then crimp the body onto the head. It would be easier to just make one drill/mill action and go through the body, head and rod and pin the whole lot. I think for ease of manufacture they just put the rod in the head and the body over the head and crimp the lot and the crimping DOES push enough of the head into the groove to hold the rod in ... but until someone pops one in a lathe and turns down the body to reveal the head I'm guessing.
Yes Rob ... the latest pics show the piston rod nose sheared off at the fore end of the splines. I'm not in a rush to blame Diana for that at this stage. I think that that particular piston assembly has been DIY'd by it's owner. The owner may have noticed that rod was wobbly and the splines area may have worked loose at that point. Maybe he managed to pull the rod out ( kept waggling it in a vice etc like pulling tooth ) and managed to work the grooved area free from the compressed parts on the head. At that point he mega glued the front part of the nose into the very front inside end of the recess in the head. He then drilled and pinned the rod in, using the crude hole we can see inside the crimp mark. Has he weakened the rod just in front of the splines whilst he was waggling it to get it out? We have no idea what DIY abuse that piston rod has experienced from it's owner as he has tried to remove and then secure it.
Last edited by bozzer; 12-01-2018 at 04:16 PM.
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Just been discussing this with landymick. He too reckons the crimp not a pin.We'll have to wait 'til the end of this diet.
I started off in the pin gang. Like I said earlier Phil, it just doesn't make sense that Diana would machine the groove, then drill/mill the hole in the head to put the pin through to retain the rod, then crimp the body onto the head. It would be easier to just make one drill/mill action and go through the body, head and rod and pin the whole lot. I think for ease of manufacture they just put the rod in the head and the body over the head and crimp the lot and the crimping DOES push enough of the head into the groove to hold the rod in ... but until someone pops one in a lathe and turns down the body to reveal the head I'm guessing.
Yes Rob ... the latest pics show the piston rod nose sheared off at the fore end of the splines. I'm not in a rush to blame Diana for that at this stage. I think that that particular piston assembly has been DIY'd by it's owner. The owner may have noticed that rod was wobbly and the splines area may have worked loose at that point. Maybe he managed to pull the rod out ( kept waggling it in a vice etc like pulling tooth ) and managed to work the grooved area free from the compressed parts on the head. At that point he mega glued the front part of the nose into the very front inside end of the recess in the head. He then drilled and pinned the rod in, using the crude hole we can see inside the crimp mark. Has he weakened the rod just in front of the splines whilst he was waggling it to get it out? We have no idea what DIY abuse that piston rod has experienced from it's owner as he has tried to remove and then secure it.
I'll then go back to what I said earlier on, if enough force is applied by the crimp to actually distort the head to retain the rod, no bloody wonder the piston bulges into a cloverleaf shape in between the crimps.
I had thought initially that the piston skirt may be slightly bigger than the head and the bulges were just in the skirt. Probably not now and more likely full depth bulges due to the heavy crimp to retain the rod.
Barry - we've had this discussion before and as I said before, I reckon they're all out of round (apart from my 3 which have all been dressed back to round)
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