Tuesday, 20 May 2014

Heanel Mod 1 DRP, Fixing and reassembly

Heanel Mod I DRP

Even though this air rifle was 75 years old there were still a lot of sharp edges on it, so I needed to get the draper mini drill out and deburr the compression tube. 

I thought it wise to clean the inside first as I didn't want to clean it with bits of deburred metal everywhere. It would also be nice to see if any damage had been caused by the nail that was embedded in the leather piston seal.

Hole left by the rivet in the piston face.

I used medium guage wire wool clamped onto and wrapped around the cleaning rod, it was dipped in white spirits and the inside of the compression tube was given a good all round scrub, and this was followed with a fine grade wire wool and then kitchen towel. 

Coarsest grade of wire wool removed most of the crud.

The inside of the compression tube was mirror smooth and shiny along the whole length, however some of the leather piston seal had stuck to the end of the tube, so I carefully chipped this off with the end of the cleaning rod. Now I could see that there were slight markings below the transfer port caused by the head of the nail, though these were nothing of concern. I did notice that the transfer port ran from the centre up to the barrel and by using the cleaning rod as a guide could see it was about 3 cm long.

White spirits stops most of the crud from collecting on the outside of the wire wool.

Using a craft blade I scraped the hard surface off the leather piston seal and shaved off any lumps and bumps off the face, 

A sharp blade brings life back to what appeared to be one knackered piston seal.

but not from around the hole left by the nail. Pouring some 3 in 1 oil into a milk bottle lid, I put the leather seal in to soak for a few hours.

Soaking in 3 in 1. A red plastic back plate give a flat surface for the leather seal to sit on.

When it came out, I placed it on a kitchen towel to soak up the excess, then pressed hard against a table surface. 

Remove as much excess oil as possible, it's going to smoke for a while as it is.

The seal appeared to have a new lease of life and a compression test proved there was new life in it now. Leather seals need a quick push to start to seal the compression tube unlike O ring and parachute seals which will seal straight off.

One restored leather piston seal.

I deburred the cocking slide and the pivot pin holes from the inside of the tube, 

Still has sharp edges after 75 years.

then screwed the grub screw for the barrel lock bar right in and deburred any metal created by the cocking linkage. 

That grub screw should come right out now.

White spirits and kitchen towel were used to remove any metal grindings from the inside of the compression tube, then I used 3 in 1 oil on some 0000 wire wool and cleaned every external surface of the rifle while it was dismantled.

0000 wire wool and oil removes rust but leaves whatever bluing is left on the action.

Now the leather piston seal was soft with no excess oil when pressed. It was screwed back on to the piston body, then the piston unit was replaced in the compression tube. 

A polish and light greasing.

The trigger housing has enough spring tension to hold the main spring in place with its preload.
With some Abby LT 2 grease liberally spread over the original main spring and spring guide, they followed on behind. I could always order a new spring later and this one was still a lot stiffer than the length of spring I ordered a while back.

The original main spring.

The trigger housing inner sleeve was still well and truly spring loaded and with it lined up, I carefully squeezed the forward end into the rear of the compression tube. I then gently tapped the rear of the rifle against the floor until the inner sleeve was back in place. 

This shows how much spring tension there is in the trigger housing.

The spring tension of the sleeve was enough to hold the main spring under preload and with the aid of a screwdriver the holes were lined up, 

All lined up.

the trigger was lined up and the pivot bolt fitted. With the safety in the off position and the trigger pushed forward, I replaced the end cap. With the end cap lined up, the retaining pin was fitted, it required the aid of a hammer to drive it home fully.

That pin takes some effort to fit as well as remove, so bear that in mind if you have to do this.

This was finger tight as there is a cut out in the stock for it to fit in.

The grub screw that holds the barrel locking detent bar unscrewed easily now that the end of the hole had been deburred.

A fair bit of wear and tear on this grub screw over the years, but it was easily fixed.

The bar and spring were removed, cleaned, greased with a little LT 2 and put back, with the head of the grub screw in a little deeper so that the cocking linkage wouldn't damage it again. 

Detent bar and spring all cleaned up.

 With a little grease on all the moving parts, the cocking linkage was slipped through the bridge and slotted into the compression tube, 

Guide for the articulated cocking linkage and threads for the fore stock screws.

the unlocking latch and breech were placed back in the forks and the pivot screw was replaced followed by the locking screw.

The pivot bolt goes in so much easier with the barrel broken.

It was a lot easier to tighten the breech pivot screw with the barrel unlocked as if it was ready to load, and this was without a breech seal in place.

The old leather breech seal was well beyond repair so I resorted to my trusty box of rubber O rings, 

Leather breach seal well beyond repair.

I did not have a three mm O ring of the right diameter so I cut one to the right size and super glued the ends together. 

New breech seal made from a section of rubber O ring.

It was made a tiny fraction larger so it would sit in the breech under its own pressure, the breech was closed to push the seal all the way home and a perfect seal appears to be produced.

New rubber breech seal fitted into place.

With the rifle lubed and put back together, I fitted it back into the stock, using a screw driver to hold the trigger tension spring back until the trigger was in place for the spring to fit over the tab.

Easing the tension spring back to fit on the back of the trigger.

Then it was a simple matter of fitting the stock screws. Each screw was fitted loosely at first allowing the action a little adjustability in the stock. This way all the screws attached correctly and then were tightened up fully. There is nothing more annoying than tightening one fore stock screw all the way home, only to find the other side won't fit.

Rifle back together, i gave the stock a rub down with wire wool to discover some lovely wood.

All I need to do now is build or bodge some sort of rear sight, the original sight is a simple affair so should be easy enough to make a rough copy. The safety still doesn't work, but I have an idea on how to remedy that, and the barrel lock could do with a new spring behind the detent bar. Anyway, the rifle fires with some authority now for it's size, but I will have to wait until I get a new chrony to find out what power it is producing.


Wing Commander Sir Nigel Tetlington-Smythe.


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