Theoben Fenman

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Theoben Fenman

Postby Tank » Tue Apr 08, 2014 8:13 pm

I suppose an argument could be made that the Theoben Fenman is not a classic. However, given the history of the gun and indeed the company itself, I would put this rifle in the "classic" category. Not the least for the innovative Gas Ram technology it uses, quite cutting edge in it's time.

Anyhow, I had this sent to me for repair, a short note on the ticket said "replace bolts". Now, that could have meant anything but not on this occasion, the two forestock screws were sticking out, with the hex drive holes well and truly rounded over. Some Neanderthal had decided to put new screws in and had forced not one, but BOTH of the forestock screws in. Until they turned no more. You see, being a bit of an older model, it has UNF fittings, the plonker had forced 5mm button heads down 3/16 UNF holes until they would go no further, then rounded them over. Anyhow I resolved that problem but had a quick look at it generally. It was absolutely knackered.

The cocking shoe is completely goosed and needs remaking and the Gas Ram has no Gas in it, which is a bit of a bugger. Theoben, when they were still in business, didn't want anyone playing with the internals o their guns, but now they are gone there are no drawings available at all, it is only learned knowledge that keeps these things going.

The first thing I need to do is get some gas into the ram and make sure it is still gas tight. If it isn't the owner is going to have to be consulted as it starts to run into money. So in order to do this an adapter was needed. The inlet for the gas (or high pressure air) is a Shrader valve. But not the outside thread fitting, the inside. This is a total arse of a thread and why people come up with such ludicrous fittings I just cannot understand, for reference the thread is Metric: 5.30 mm OD × 0.706 mm pitch or in Imperial: 0.209 in OD × 36 tpi. Bonkers. Anyhow, I have the adapter made now:

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Re: Theoben Fenman

Postby Kemik » Sun Apr 20, 2014 6:48 pm

I recently resealed my hw90 a gas ram wiehrauch / theoben project, I had an adapter made to fit and used a mountain bike shock absorber pump to get it up-to pressure 18 bar seems about right, not sure what pressure the Fenman is tho but if it's below 20 bar your welcome to borrow the pump.

Steve
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Re: Theoben Fenman

Postby Tank » Sun Apr 20, 2014 7:20 pm

Very kind offer Steve but I have a couple of High Pressure pumps and air supplies, but thank you.

This all ended in tears anyway. As many of you will know there are no spares available for the Theoben guns but there are a number of us manufacturing spares but one of the major problems with this particular series is the weakness of the actual gas ram cylinder. Although the design is good in principle and the cocking linkage is innovative the actual cocking shoe, which is unhardened mild steel, bears directly against the wall of the gas ram cylinder which is also unhardened mild steel.

Obviously, no matter what lubrication you use, with the two surfaces working against each other something has to give and it is usually the wall of the cylinder, letting the pressurised gas escape. This was indeed the case and as soon as I tried to pressurise the cylinder there was an immediate hiss of escaping air. I have left the decision making with the customer, he is of course quite unhappy as his "friend" sold him the rifle at a bargain price. Say no more.
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Re: Theoben Fenman

Postby Kemik » Sun Apr 20, 2014 7:36 pm

My hw90 has a nylon 'shoe' that the linkage sits in as I remember, I can't see a company going to the trouble of changing a working design (unless it was crap) for every new gun or wiehrauch improved the theoben design.

But I am no expert

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Re: Theoben Fenman

Postby Tank » Wed Apr 23, 2014 1:26 pm

Hi Steve, the early Theoben guns are a completely different animal to the later HW90. Weihrauch redesigned the cocking linkage/attachment and the trigger housing. They are very "agricultural" on the Fenman. Remember, much of this gun is a cobbled together BSA Meteor cocking lever and some Webley internals. Ian Jones actually has a Gas Ram Webley and even Webley don't want to know. Speaks volumes. Also, some are Gas ram and some are Air ram. This particular gun in question is Gas. Which would not be a problem for me as I have access to lots of various high pressure gases but no point unless the chap either buys a complete ram kit for the 90 and adapts it AND makes a cocking shoe or has me make a new cylinder which is not without it's own set of problems. Or put a spring in there and turn it into a HW80.
Shame really as this was the forerunner to the HW90 and could really have been something instead the Weihrauch became the gun it should have been. However it is interesting to note that although the HW90 was the first of the Weihrauch Gas Ram guns it appears to be the last. They are notoriously difficult to make and above all, expensive.
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