Well, the gas ram seems to be going south in my Titan

[56S]

About 4,500 shots and FPS at 15' is down almost 100 from when new.  Using the 14.3 gr Crosmans I used to get a consistant 742 +- up until last week when I was getting around 700.  I figured it was due to the gun being cold.  Today was in the high 60's and FPS is around 650.  Seal is good and the breech seal passes the tissue test.  Fresh clean and lube, same thing.  I noticed an oil ring on the chrome ram where there was none before.

Question, get another Crosman or is there a better replacement out there?  I do have the dimensions of the gas ram.

[BenjiHunter]

It survived 45000 shots. That's pretty good.

[56S]

One too many zeros.  4,500 shots.

[Motorhead]

Would suspect a buggered up piston seal before the gas ram failing.

[Roadworthy]

One thing to consider is the age of the gun - are you still within the one year warranty period?

[56S]

The piston seal is in great shape.  This gun was a reman with a thirty day warranty.  It does seem to be easier to cock but them I've been shooting the D45 more that the Titan lately.  The real clincher is the ring of oil about 3/4" from the end of the ram.  Ever had a motorcycle with a leaking fork seal?  looks the same way.  There is no reason for that oil to be there.

[JR]

Do you have Gene's bushing on the ram to keep the shaft centered? I have heard of some Crosman guns that had the ram fail because the shaft is on a angle and wears the seal in the ram out.

[Wood Boats]

Ever had a motorcycle with a leaking fork seal?  looks the same way.  There is no reason for that oil to be there.

Never had an old Trumpet that did not have at least one leaky seal.  Where I disagree is there is always a reason for oil to be where it should not be.  I do agree that oil should not be where you describe but there will be a reason for it presence.

I have nothing to go on but a hunch here but did the gun have any play in the cocking motion?  I am guessing that there is (or was) a side load somewhere during the cocking motion to cause the failure of the seal in the ram.  (the reason for the oil to be where it should not be)

There were some threads here for the first shots at converting guns to gas rams that showed some funny wear patterns until the install procedures were figured out.  Fit of the parts should be more critical with the ram than with a spring powered gun.  Any side loading to a gas ram is the kiss of death.

Look for wear on the cylinder.  Inspect the ram closely and it will tell you what happened. 

Can you post some pics of the parts?  Any funny wear patterns? 

[OleTomCat]

You can replace the ram with one from Crosman or take it out measure it and try to see if it is close enough to an N-Forcer MF19-125-Red that you can get one of them in there.  These things see more cycles in a day than most air rifles see in their entire lifetime.....

I am currently trying to fit one of these in my Gamo Big Cat, it is taking some major work be we will see how it turns out

http://www.n-forcer.com/index.php/products

[56S]

Do you have Gene's bushing on the ram to keep the shaft centered? I have heard of some Crosman guns that had the ram fail because the shaft is on a angle and wears the seal in the ram out.

My Titan has a concave cup on the inside of the piston where the convex end of the piston fits.  The opposite end of the ram fits nicely in the end cap with very little play.  There is no evidence of the body of the ram ever touching the inside diameter of the piston and no wear marks on the piston skirts.  It is actually very hard to tell by the piston wear just how far the piston is compressed.

Tom,  My piston measures:  cyl dia, 18.1mm  piston dia, 9.93mm  cyl length, 150.9mm  piston length, 109.92mm and OAL 260.42 or about 10 1/4" long when extended. 

I'll lake a look at the linked site and see if one of them can be adapted to suit my gun.

[OleTomCat]

Do you have Gene's bushing on the ram to keep the shaft centered? I have heard of some Crosman guns that had the ram fail because the shaft is on a angle and wears the seal in the ram out.

My Titan has a concave cup on the inside of the piston where the convex end of the piston fits.  The opposite end of the ram fits nicely in the end cap with very little play.  There is no evidence of the body of the ram ever touching the inside diameter of the piston and no wear marks on the piston skirts.  It is actually very hard to tell by the piston wear just how far the piston is compressed.

Tom,  My piston measures:  cyl dia, 18.1mm  piston dia, 9.93mm  cyl length, 150.9mm  piston length, 109.92mm and OAL 260.42 or about 10 1/4" long when extended. 

I'll lake a look at the linked site and see if one of them can be adapted to suit my gun.

Click on this link, it will open a PDF: http://www.n-forcer.com/content/pdf/Mini.pdf

Scroll down to the MF19-125 MM, It should be:

                   Overall            Tube
Stroke         Length            Length
125.0mm    295.0mm        170.0mm
4.92"           11.61"               6.69"

[56S]

Thinking the -100 may work with a spacer.  Bad day at work and only a minute to compare dimensions

Edit:  Looked at the 100 and since my piston is 109 and I believe the oil ring was about 3/4 of an inch from the end it just may be close.  As time permits I will pull the ram, place an Oring on the piston and cock it to check total piston travel.  I like the idea of having an adjustable ram since the local airport has a nitrogen tank for aircraft landing gear struts.  Finding the fittings to mate the two may be a problem.

[OleTomCat]

Thinking the -100 may work with a spacer.  Bad day at work and only a minute to compare dimensions

Edit:  Looked at the 100 and since my piston is 109 and I believe the oil ring was about 3/4 of an inch from the end it just may be close.  As time permits I will pull the ram, place an Oring on the piston and cock it to check total piston travel.  I like the idea of having an adjustable ram since the local airport has a nitrogen tank for aircraft landing gear struts.  Finding the fittings to mate the two may be a problem.

100mm won't work, stroke is too short.  To get the 125mm to work you will either have to remove some metal from the Piston or the back block to allow for the longer tube of the 125mm ram...

[56S]

I have never measured the true stroke.  Have you?  Only because I remember the oil ring on the piston being some distance from the end is why I thought 100 mm might be enough.  Another consideration is the OAL.  I'm at 10.25 and the 125 is 11.61"  Stuck in the middle again.

[OleTomCat]

You did when you provided the number below:

Tom,  My piston measures:  cyl dia, 18.1mm  piston dia, 9.93mm  cyl length, 150.9mm  piston length, 109.92mm and OAL 260.42 or about 10 1/4" long when extended. 

The Piston length is the stroke of the ram, now factor in a little preload lets say 5mm and you have an affective stroke of about 104mm.

If you have access to a mill or even a really good Drill press you can recess the ram backstop, that would be the first chunk of steel that you remove from the gun when disassembling, about 10mm or so and that may give you what you need, if not then you have to start  taking it out of the Piston to allow more of the body of the ram to fit up inside.  On the Gamo Big Cat I just converted I removed over half an inch of material from the piston and the other half inch from the trigger block.  It shoots really well, but only 12fpe, I really lightened the piston, I am going to try turning the ram around tomorrow and shoot it that way to see if it improves any....

[56S]

I'm thinking the rifle does not use the full stroke of the piston.  That's what I'll need o check.  I think there's very little metal that can removed from the end cap.

[OleTomCat]

I'm thinking the rifle does not use the full stroke of the piston.  That's what I'll need o check.  I think there's very little metal that can removed from the end cap.

It uses at least 4" which is about 104mm, and why a 100mm won't work.

[56S]

Ah ha!  Saved me from tearing it down.  Thanks.  Plan B?

[OleTomCat]

Ah ha!  Saved me from tearing it down.  Thanks.  Plan B?

Two choices:

          1.) Go back with the OEM ram (BT9M22-03-100B) from Crosman, easiest thing to do order it open it up and drop it in...

          2.) Get an N-Forcer MF19-125-red or yellow, and drill or mill out enough of the back block as needed to get the MF19 in place, about 15mm....

Need any help or advice let me know...

[56S]

Just in case I changed the breech seal.  No change other than the seal protrudes too far out and I am not getting full closure until it settles in place.  This morning before work I shot a few rounds and they were in the 680s when the gun was about 34 degrees.  Tried it again when I got home and the same when it was 20 degrees warmer.