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Front Triangle
http://forum.alienslegacy.com/viewtopic.php?f=3&t=9737		 Page 1 of 2
Author:  propmainiac [ Sun Mar 27, 2011 4:43 pm ]
Post subject:  Front Triangle
Hello
Does anyone know how thick the metal is for the front triangle on the pulse rifle? Fabricating my own at the moment and I'm using steel bar-stock but looks too thick. I'm attaching it to a piece of copper pipe and I was going to attempt to solder it together. I have some 16 gauge steel that I was planning on fabricating the barrel vent from. Is the triangle the same thickness as the barrel vent? I'm planning on creating a 8 hole vent. Also is the triangle attached to the vent? Its obvious it is on the ten hole but not so sure on the 8 hole.
Author:  Bug Stomper [ Sun Mar 27, 2011 10:46 pm ]
Post subject:  Re: Front Triangle
The front triangle and the barrel vent are one piece on both the su 10 hole and 8 hole versions.
The barrel vent as well as the shoulder stock are made from 40mx40mm square tube with a wall thickness of 3mm. After milling out the slots, the barrel vent/front triangle is then bent giving it a quite characteristic shape. Finally the barrel support tube and (in case of the 8 hole version) the sling loop are welded to the barrel vent. The barrel support tube is 25.4mm (1") long and has an outer diameter of about 24mm.
I know these dimensions differ quite a bit from the parts generally offered for the pulse rifle. But check the available reference material for yourself...

Cheers,
Stefan
Author:  Xhiwar [ Sun Mar 27, 2011 11:32 pm ]
Post subject:  Re: Front Triangle
I always thought on the 8-hole rifles, the barrel vent and the trianlge were separate pieces. But then again, maybe I just think that way because SD is offering them as separate pieces. I'd have to take a look at the reference pics again.

But I'm fairly certain that the diameter of the triangle tube is only about 22mm. Length should be at about 1", that's right, but 24mm is too wide. Even if you assume that the barrel is 19,05mm in diameter (I have to side with b26354 here and say that I don't think it's more than 18mm), a 24mm diameter ring seems too large. Maybe we should call HCG and have them measure the diameter on the real thing. ;)

Cheers!
Roman
Author:  Bug Stomper [ Mon Mar 28, 2011 7:21 pm ]
Post subject:  Re: Front Triangle
Yeah, some reliable intel on this would be nice!

Neverttheless, if you look at the pictures at Harry's site (http://www.harryharris.com/opr09.htm) you can see that the HGC version is definitely too small in diameter.
The picture also shows that the front triangle and the barrel vent is actually one piece.

Cheers,
Stefan
Author:  Xhiwar [ Mon Mar 28, 2011 7:24 pm ]
Post subject:  Re: Front Triangle
I believe on most current replica Pulse Rifles, the barrel diameter is about 14mm, and from what I've seen, the HCG has copied that mistake as well.
But yeah, now that I see it, the 8-hole vent really is one piece as well. You learn something new every day. :D

Cheers!
Roman
Author:  Harry Harris [ Mon Mar 28, 2011 7:58 pm ]
Post subject:  Re: Front Triangle
Bug Stomper wrote:
you can see that the HGC version is definitely too small in diameter.

But they had an original PR to reference from!

I'll say that again: They had an original PR to reference from!

:?

Harry
Author:  b26354 [ Mon Mar 28, 2011 8:55 pm ]
Post subject:  Re: Front Triangle
HCG front tube is 3/4" diameter and the barrel is about the same diameter as the end of an unmodified Thompson barrel (minus the foresight)

Image

but they missed the BFA/barrel extension (visible in the pics on Harry's site and in the BAPTY photo of the rifle with the 10 hole vent) which adds a couple of mm to the diameter at the end i.e a 7/8" diameter tube is required

Image
Author:  Noble [ Mon Mar 28, 2011 9:21 pm ]
Post subject:  Re: Front Triangle
There was some "confusion" on the RPF about this.

There is some variation from firing thompson PRs to dummy thompson PRs.

I personally want my rifle to be like the firing PR.
Author:  Harry Harris [ Mon Mar 28, 2011 9:33 pm ]
Post subject:  Re: Front Triangle
There shouldn't be any variation as the stunt PRs for the film were cast from a practical prop.

I have a cast of one of the stunt PR's (A Darkside of the Moon version) and the outside diameter of the 'triangle tube' is indeed 22mm with the outside diameter of the barrel itself at 18mm.

Harry
Author:  Bug Stomper [ Mon Mar 28, 2011 10:52 pm ]
Post subject:  Re: Front Triangle
Harry,
do you know which generation it is? I ask as there's always some shrinkage.
Let's consider this:
1. Moldmaking of the original
2. Casting of the stunt version
3. Molding of the stunt version (Darkside of the Moon)
4. Casting of your copy.

So there have been at least 4 casting steps (2. Generation) each with a little amount of shrinkage (usually 0.5-3% depending on the materials used).
Assuming a shrinkage of 1.5% per casting step the part will be about 6% smaller (0.985*0.985*0.985*0.985=0.941).
The barrel diameter of an unaltered Thompson is 19.05mm at the muzzle.
So 19.05mm*0.941= 17.92mm which is quite close to the 18mm measured on the cast of the stunt.
Now one can surely argue that the shrinkage might be lower in this case, but then again we don't know if it's really a second generation cast or maybe even a third or later...

Cheers,
Stefan
Author:  PVB [ Mon Mar 28, 2011 10:57 pm ]
Post subject:  Re: Front Triangle
Harry Harris wrote:
Bug Stomper wrote:
you can see that the HGC version is definitely too small in diameter.

But they had an original PR to reference from!

I'll say that again: They had an original PR to reference from!

:?

Harry

Do you know if it was a Hero PR or a stunt version?
Author:  Harry Harris [ Mon Mar 28, 2011 11:03 pm ]
Post subject:  Re: Front Triangle
PVB wrote:
Do you know if it was a Hero PR or a stunt version?

It was a non-functioning practical version IIRC, with a deactivated Thompson. Aluminium shroud, all metal, the works. EDIT: Ahh, I see what Jon means now; the barrels of the non-functioning practical PRs were welded-on metal tubes and not the original Thompson barrels. That may account for the discrepancies in size.

Bug Stomper wrote:
Harry, do you know which generation it is?

I bought it a L-O-N-G time ago so I'm assuming that it's a cast of one of the original stunt PRs, but I don't know for certain. The only thing I can say is because of it's age and the fact that there weren't that many around back then I'm lead to believe that it is what I think it is, if that makes sense!

Harry
Author:  PVB [ Mon Mar 28, 2011 11:04 pm ]
Post subject:  Re: Front Triangle
So, as you say, the HCG one is identical to the original weapon. Suits me. 8)
Author:  Bug Stomper [ Mon Mar 28, 2011 11:29 pm ]
Post subject:  Re: Front Triangle
Actually, the HCG barrel is only 16.5mm in diameter. This is more or less the minimum diameter of the Thompson barrel.
The original barrel however has a "step" to which the front sight is mounted to. This step has a diameter of 19.05mm.
This step is missing on the HCG barrel as well as the taper of the barrel towards the rear.

Cheers,
Stefan
Author:  b26354 [ Tue Mar 29, 2011 12:12 am ]
Post subject:  Re: Front Triangle
Bug Stomper wrote:
This step is missing on the HCG barrel as well as the taper of the barrel towards the rear.

Cheers,
Stefan


I shed a tear every time I see someone chop the barrel off of their Marui Thompson and replace it with a straight tube :(

If HCG really did have access to a complete PR - they chose to ignore some details.
Author:  Bug Stomper [ Tue Mar 29, 2011 4:33 pm ]
Post subject:  Re: Front Triangle
b26354 wrote:
I shed a tear every time I see someone chop the barrel off of their Marui Thompson and replace it with a straight tube :(


I could not have phrased it better!

Cheers,
Stefan
Author:  Bug Stomper [ Tue Mar 29, 2011 10:44 pm ]
Post subject:  Re: Front Triangle
Just found a few more evidence pieces regarding the barrel diameter and the barrel support tube.
There are still some things that don't add up but these seem to support the 7/8" (22,22mm) theory for the barrel support tube diameter.
I'll go into more detail after some more research....

Cheers,
Stefan
Author:  Matsuo [ Tue Mar 29, 2011 11:27 pm ]
Post subject:  Re: Front Triangle
If you guys want to split hairs that's fine but the gun we patterned off of had a straight barrel on it. It appeard to have been a thin profile barrel with a blank adaptor welded on and then turned on a lathe or spun against a belt sander to clean it up. Now, I cannot answer difinitively weather this setup was put on the gun after production by bapty so that they could keep the factory barrel un modified or if it was like this all along.

We made some compromises in the barrel and vent in order to keep the price down, a tapered barrel would have added an apreciable amount to the overall cost off the unit, pusing it over the $1000 mark which I fought very hard to.

M
Author:  Bug Stomper [ Wed Mar 30, 2011 2:38 am ]
Post subject:  Re: Front Triangle
Hi Matt,

this is not intended to bash your/HCGs work. Actually I think its a really nice replica! (I have one too btw.)
However, there are certain things that are not true to the originals (and that refers to all pulse rifles I've seen so far not only the HCG one) and some hardcore nerds like us would like to get them right.
There was a blank adapter welded to a thin walled barrel? That's a version I haven't seen before. Do you have any pictures of it you can share? Maybe even some dimensions? ;)
I might be wrong there, but I'd guess that the original Thompson barrel was replaced when the PR was deactivated after filming. The blank adapter wasn't needed anymore, so they welded it to the replacement barrel. I don't think they ever fired any blanks from the replacement barrel as the chamber was gone with the original barrel.

Some additional questions if you don't mind:
Was the barrel welded to the receiver?
Was the barrel vent spot welded to the SPAS cage?
Did the SPAS cage have the screw to hold the GL front block?

Cheers,
Stefan
Author:  Xhiwar [ Wed Mar 30, 2011 9:56 am ]
Post subject:  Re: Front Triangle
Absolutely no bashing of the HCG rifle intended.
In fact, I'm glad it was under 1000$, gave me the opportunity to get a set of aluminum shrouds. People who simply dismiss it as a "disaster" or a bad replica are either deluding themselves about how much a Pulse Rifle with all the bells and whistles costs (a LOT more than 1000$) or simply didn't read the description before buying the HCG rifle.
But even though it is a great replica, it does not 100% replicate the screen-used rifles, e.g. the stock mechanism (which might be an improvement over the "mechanism" on the real rifles). This thread has somewhat turned into a research thread about finding the correct diameter on the rifles with the extended Thompson barrels.

Cheers!
Roman
Author:  b26354 [ Wed Mar 30, 2011 11:40 am ]
Post subject:  Re: Front Triangle
Xhiwar wrote:
This thread has somewhat turned into a research thread about finding the correct diameter on the rifles with the extended Thompson barrels.

Roman


Didn't this thread start out as a "research" thread into front triangle dimensions :)

For what it's worth, I have 2 HGC's and one of them is going to be dismantled for a Hudson M1A1, real SPAS and Maruzen Remington to fit inside so, not bashing, just trying to understand where the 16mm diameter barrel came from.

Actually - I just found some pics of the insides of a BAPTY rifle that has a straight tube welded to the Thompson receiver.

Anyone remember a member who posted pics of 2 BAPTY rifles he was restoring back in 2004?
Author:  Matsuo [ Wed Mar 30, 2011 1:53 pm ]
Post subject:  Re: Front Triangle
Quote:
However, there are certain things that are not true to the originals (and that refers to all pulse rifles I've seen so far not only the HCG one) and some hardcore nerds like us would like to get them right.


As mentioned we had to make some tough decisions in order to bring the thing to market with the metal shrouds and keep it under $1000.


Quote:
There was a blank adapter welded to a thin walled barrel? That's a version I haven't seen before. Do you have any pictures of it you can share? Maybe even some dimensions?


I cant share any pix as they are not mine to share sorry, I can ask though.

I mis-spoke the gun we used primarily HCG owned, it had a thin walled barrel as far as I could tell there was no blank adapter in it. We referenced off another gun I believe it was one the propstore owned, it had the blank adapter permanently affixed.


Quote:
Was the barrel welded to the receiver?


Yes it was.


Quote:
Was the barrel vent spot welded to the SPAS cage?


Yes it appeared to be brass brazing actually.

Quote:
Did the SPAS cage have the screw to hold the GL front block?


Oddly enough there was only one screw on the right side none on the left.



M
Author:  Bug Stomper [ Wed Mar 30, 2011 2:15 pm ]
Post subject:  Re: Front Triangle
Matt,

thanks a lot for the additional input! I'm now pretty sure which pulse rifle you had for reference.
It would be great if you could get the permisson to post some additional reference pictures and/or dimensions. After all you know the saying - "A picture says more than a thousand words" :D


Jon,

iIrc, the restoration was done by Karl Derrick.

Cheers,
Stefan
Author:  Matsuo [ Wed Mar 30, 2011 2:29 pm ]
Post subject:  Re: Front Triangle
For what it's worth, the metal used for the vent was easily twice as thick as what anyone has ever used on vents, Including myself, SD, or DeanO.
For ease of manufacturing everyone has chosen to use thinner gauge sheet, however the original vents were born of welded square tube; cut, milled and finally bent into the triangle shape we know.

For those of you who want absolute accuracy, this is waht you have to do, no storebought piece will do. ;)

M
Author:  Bug Stomper [ Wed Mar 30, 2011 4:08 pm ]
Post subject:  Re: Front Triangle
I'm glad you can confirm what I said above. :D
And as I brought up the thing with the thousand words:

Image

From left to right: Raw material, barrel vent, shoulder stock and buttplate before bending and welding.

Cheers,
Stefan
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