Tuning Relum 322 (Tornado)

[Lumphammer]

Hi there,

I have recently made some modifications to a Relum 322 which I would like to post so that others can possibly do the same if they wish.

My Relum was originally my fathers gun which he bought new in the early 60's, and as a young teenager i learned to shoot with it - The internet suggests these guns are Hungarian donkeys and useful for nothing more than hammering fence posts in but for some bizarre reason i quite like it and I've spent significant time making it "good".

The rifle has a 26mm chamber with a stroke of ~80mm delivering a swept volume of 42474 cubic millimeters, the transfer port to the loading tap is on the diagonal and 5mm in diameter with a length of 28mm giving a transfer port volume of 550 cubic millimeters. The static compression ratio is 77:1 which is probably responsible for some of the guns poor performance especially with synthetic seals.

This is the exit of the 5mm transfer port into the loading tap:



My cylinder was slightly out of round and somewhat scared from decades of use, i honed this (if honed is appropriate for such a crude process) with a tightly bound roll of scotchbrite on a rod attached to a drill. The results were better than expected and restored the finish a great deal.

After experimenting with a parachute seal from a HW77 i decided that my out of round cylinder was not going to work, hereafter i used O-ring seals

I machined several brass piston heads to mount on the standard carriage. My final dimensions for the head is 25.5mm OD head, 8mm deep with a single 20mm ID x 3mm cross section nitrile O-ring. The O-ring sits in a slot which is 3.05mm wide and has a 20.75mm centre.

This is a similar piston head i experimented with, the final is the same bar the above dimensional changes:

The carriage has a 7mm hole where the rivet previously fastened, the brass piston head is bolted though using a slotted head bolt i machined and secured with a nyloc nut

At the other end, the spring has been replaced with a mainspring from a Meteor, I machined a new back stop to have 13mm of extra preload and an integrated spring guide.



The full inside assembly:



This resulted in a velocity of 428ft/s (426, 427, 428, 428, 428) with Superdomes giving 5.9 ft lbs - however it also gave horrendous noise, vibration and wear to the end of the piston head. This was the massive transfer port causing insufficient back pressure to stop the head to slamming into the end stop.

To prevent this i needed to increase the compression ratio, this was done via sleeving the transfer port. As stated the transfer port is 28mm x 5mm, i machined a sleeve with a 2.5mm ID x 25mm long 4.95mm on one side and 5.05mm on the other. The sleeve has a 60 degree entrance and exit.





Fitting this pin on a diagonal from inside the chamber was a challenge!!! I used a long rod, a dead centre attached to a metal rod, soft blow hammer and a lot of patience.



Sleeve half fitted:



Sleeve fully inserted and seated:



The exit of the sleeve is visible behind the tap loader through the barrel:



The fitting of the sleeve has had a dramatic effect, not only does the gun not try to dismantle itself on firing the power output has risen substantially. I don't have a chronograph with me but whereas at 5.9ft lbs i was burying pellets tail deep into a piece of pine i am now putting the tail between 5 and 8mm below the surface. I suspect in the region of 10ft lbs but i will report back when i have had it tested with a chronometer.

Don't get me wrong, it is still a very agricultural gun and the cocking effort with 13mm preload is heavy but i am very happy with the result.



Last to do is to re blue the barrel and sand & oil the stock.

I must say thanks to a member on this forum called T20, whilst he did not help me directly his thread on improving the B2 rifle gave me a good nudge in the right direction with regards to sleeving the transfer port to increase compression ratio.

Regards,

Tom

[T 20]

Hi Tom and welcome to the BBS.

What a fantastic first post, I really enjoyed reading that and couldn't believe it when you mentioned me at the end.

I'm glad you found my post on the b2 usefull, the angled transfer port on the b2 always reminded me of the port on the Tornado --- you did very well to get a sleeve in there.

When I have built O ring piston heads for Rellums in the past I made them slightly different to yours --- I machined the brass heads with a two diameter stub on the back.

http://i1138.photobucket.com/albums/...s/DSCF1276.jpg

The larger stub OD being 7mm the smaller OD being 1/4" and threaded at 1/4"unf.


I have a Rellum Telly waiting in the wings to be O ringed so it will be interesting to see what that's like when it's sorted.






All the best Mick

[Lumphammer]

Thank you Mick and thanks for the information you have put in the public domain to help others.

The angled transfer port was a problem, it was my reasoning for not going the whole 28mm but with hindsight i could have gone for around 27mm on the sleeve. As this was a one shot your B2 figure of 2.5mm for the ID "feels" about right. The static compression ratio is around 230:1 versus 77:1 previously.

I forgot to mention that i cut a washer from nitrile sheet to go between the piston head and carriage - this will be removed since it appears to be doing nothing.

Do you have any knowledge of how Relum attached the tap loader housing to the piston tube? I found some debris suggesting brasing but i feel this is unlikely...?

Regards,

Tom

[TonyL]

Hi Tom,

And a big welcome to the forum.

I can see that you're going to be an avid subscriber to the technical side on the springers.

Excellent first post and very nice looking internals.

Enjoy!!

[original45]

That is fantastic .my old relum had a tune.nothing more than a debure,meteor Titan spring.I believe a webley synthetic seal and spring sleve and a floating guide .it was far better than standard.its been said many times making something far better than its standard form is so rewarding.I may re strip mine now and look at a o ring seal.great job excellent work.love it.

[Lumphammer]

Thank you both,

Good luck with you Relum original45, if you do the same as i did (i.e. pre tension on the Meteor spring) you must sleeve the transfer port otherwise the result is unbelievably bad. After firing several shots one after another i had to put the gun down for a while as i had ringing and pain in my trigger finger! I'm not joking either, it was that bad!

Regards.

Tom

[junglie]

I restored a one for a freind that had sentimental value(it was his dad's) I honed the piston out to take a bsa airsporter spring I happened to have lying around , fItted a floating guide & managed to get it up to 8.5 ft/lbs but accuracy was very poor. Then I noticed the back sight was'nt vertical, neither was the front ? turned out the barrel was loose, looked like it was just glued in place, no trace of brazing. fixed it with superglue(it was just a relum) & fine after that. Might help anyone who finds theirs can't hit a barn door too. The large transfer port explains a lot. I prefer leather seals & as his was fine after a good soak in hempseed oil overnight just left that unchanged. It shot a lot better but still harsher than I'd have liked so I may have another go at it & sleeve the port down a tad(If I ever get that desperate for projects..LOL)

[T 20]

Thank you Mick and thanks for the information you have put in the public domain to help others.

The angled transfer port was a problem, it was my reasoning for not going the whole 28mm but with hindsight i could have gone for around 27mm on the sleeve. As this was a one shot your B2 figure of 2.5mm for the ID "feels" about right. The static compression ratio is around 230:1 versus 77:1 previously.

I forgot to mention that i cut a washer from nitrile sheet to go between the piston head and carriage - this will be removed since it appears to be doing nothing.

Do you have any knowledge of how Relum attached the tap loader housing to the piston tube? I found some debris suggesting brasing but i feel this is unlikely...?

Regards,

Tom

No need to thank me Tom --- I just do what I do for a laugh.

After years of reading tuning articles on how opening the transfer port up gained power, I just decided to close one up and see what happened.

Jim Tyler and Professor Mike's articles in Airgun World over the last couple of years have shown us why the transfer port size is so critical.


It's interesting to note from your first post that the Tornado cylinder dimensions are nearly the same as a HW77/97 and that now you have sleeved the transfer port down this is very close to the size of that on a 2012 Walther LGV.


Unless the Nitrile washer you use is quite thick (5-6mm) I doubt it would do much --- IIRC Ed Canoles in the States tried a thin Nitrile washer on one of his O ringed guns and found no advantage.

I have no idea how the tap housing is attached to the cylinder on the Tornado --- it could well be brazed on as this method of fixing was used by many manufacturers.


And if you'd like to come and play don't forget you're just down the A5 from my place and this :-

http://www.airgunbbs.com/showthread....25#post5877025





All the best Mick

[gedfinn 2]

Hi there,

I have recently made some modifications to a Relum 322 which I would like to post so that others can possibly do the same if they wish.

My Relum was originally my fathers gun which he bought new in the early 60's, and as a young teenager i learned to shoot with it - The internet suggests these guns are Hungarian donkeys and useful for nothing more than hammering fence posts in but for some bizarre reason i quite like it and I've spent significant time making it "good".

The rifle has a 26mm chamber with a stroke of ~80mm delivering a swept volume of 42474 cubic millimeters, the transfer port to the loading tap is on the diagonal and 5mm in diameter with a length of 28mm giving a transfer port volume of 550 cubic millimeters. The static compression ratio is 77:1 which is probably responsible for some of the guns poor performance especially with synthetic seals.

This is the exit of the 5mm transfer port into the loading tap:



My cylinder was slightly out of round and somewhat scared from decades of use, i honed this (if honed is appropriate for such a crude process) with a tightly bound roll of scotchbrite on a rod attached to a drill. The results were better than expected and restored the finish a great deal.

After experimenting with a parachute seal from a HW77 i decided that my out of round cylinder was not going to work, hereafter i used O-ring seals

I machined several brass piston heads to mount on the standard carriage. My final dimensions for the head is 25.5mm OD head, 8mm deep with a single 20mm ID x 3mm cross section nitrile O-ring. The O-ring sits in a slot which is 3.05mm wide and has a 20.75mm centre.

This is a similar piston head i experimented with, the final is the same bar the above dimensional changes:

The carriage has a 7mm hole where the rivet previously fastened, the brass piston head is bolted though using a slotted head bolt i machined and secured with a nyloc nut

At the other end, the spring has been replaced with a mainspring from a Meteor, I machined a new back stop to have 13mm of extra preload and an integrated spring guide.



The full inside assembly:



This resulted in a velocity of 428ft/s (426, 427, 428, 428, 428) with Superdomes giving 5.9 ft lbs - however it also gave horrendous noise, vibration and wear to the end of the piston head. This was the massive transfer port causing insufficient back pressure to stop the head to slamming into the end stop.

To prevent this i needed to increase the compression ratio, this was done via sleeving the transfer port. As stated the transfer port is 28mm x 5mm, i machined a sleeve with a 2.5mm ID x 25mm long 4.95mm on one side and 5.05mm on the other. The sleeve has a 60 degree entrance and exit.





Fitting this pin on a diagonal from inside the chamber was a challenge!!! I used a long rod, a dead centre attached to a metal rod, soft blow hammer and a lot of patience.



Sleeve half fitted:



Sleeve fully inserted and seated:



The exit of the sleeve is visible behind the tap loader through the barrel:



The fitting of the sleeve has had a dramatic effect, not only does the gun not try to dismantle itself on firing the power output has risen substantially. I don't have a chronograph with me but whereas at 5.9ft lbs i was burying pellets tail deep into a piece of pine i am now putting the tail between 5 and 8mm below the surface. I suspect in the region of 10ft lbs but i will report back when i have had it tested with a chronometer.

Don't get me wrong, it is still a very agricultural gun and the cocking effort with 13mm preload is heavy but i am very happy with the result.



Last to do is to re blue the barrel and sand & oil the stock.

I must say thanks to a member on this forum called T20, whilst he did not help me directly his thread on improving the B2 rifle gave me a good nudge in the right direction with regards to sleeving the transfer port to increase compression ratio.

Regards,

Tom

Well written Tom, & Thanks for that ! Some good work there,
All the best, Ged.

[Lumphammer]

Thank you for the invitation Mick but i think i would be out of my depth armed with just with my poor eye and the old swamp donkey

Weather permitting i hope to go to our local MK air rifle club this Sunday to test the old girl out. I have a late start to work tomorrow so will have the gun tested on a chronograph in the morning.

Do you know anything about the scope rails Relum used and what mounts they take? They are a single dovetail bent from sheet, the top of the dovetail is 18mm going down to 15mm.

Tom

[Lumphammer]

Sorry for the delay, as a newcomer i think my posts have been taking a while to be moderated. The results from the chronometer average 563 fps which i am very happy with.

I think this is about the limit for the Relum in this configuration, with hindsight i think the static compression could do with being in the 300:1 region which should be just about possible for a Tornado.

Regards,

Tom

[T 20]

Thank you for the invitation Mick but i think i would be out of my depth armed with just with my poor eye and the old swamp donkey

Don't get the wrong impression of the day at my place Tom, it's just a fun day out for Boinger users, and I'm no gun snob --- one of the guns I shall be using is the b2 I wrote about on here.

Do you know anything about the scope rails Relum used and what mounts they take? They are a single dovetail bent from sheet, the top of the dovetail is 18mm going down to 15mm.

Tom

It sounds like the rails are about the same size as pre 1965 BSAs --- Sportsmatch do special mounts for these and John Knibbs sell clamp on adaptors to reduce the dovetail to 11mm.


Edit:- I think these are what you want Tom

http://www.sportsmatch-uk.com/white




All the best Mick

[TonyL]

I'll be working on one of these soon for a work colleague and I've just stumbled across this.

Will have a proper read later, as I'm at work now, although I don't think we'll see too many customers today with the conditions.

[TonyL]

Mmmmm.....I wonder if my work colleague might want to go down the route of a proper tune and sorting the SCR, or if he'll just want it in "working" order, inefficient and with the twang. Monsieur Tinny Bum is more than happy to do me a top hat & guide for the chosen spring if the chap will at least let me go that far. He's not a "shooter", just that the rifle has sentimental value as it was his father's rifle. We'll see.