Monthly Archives: February, 2012

Tuning HW30s or R7 Part- II Problem Identification

Ok! Now we are going to understand what needs to be look at. And why it is required to tune.

Lets follow the picture.

Here we are going to remove the cocking arm. There are two pin that needs to be removed in order to remove the required piece. There is another way too. By removing the main screw that holds the barrel with the receiver can be removed too. But this is simple way.

The next pin too has to be removed.

Now you see the cocking arm is removed. Interestingly if you

Closely, the surface of the receiver badly damaged.

Also see the cocking arm link. Bad in shape. That means metal to metal friction was heavy. So we have to reduce the excess material from the link and polish it. Also we have to File-off few micron of material from the receiver and then polish and blue them.

Not bad after bluing.

It is important to deburr carefully the arrow marked areas. While doing that, just keep in mind, while you will enter the seal, it may cut. So you have to remove all that possibly can cut the seal.

Also you see, the receiver is honed. The ID was Phospheted  from factory to avoid rusting. But it will also avoid nicely lube that important for seal.  Don’t worry about the rust. Go ahead and  hone the receiver with 320 girt if you are doing it with low speed. If you are good with hand tool you can go with high speed honing and in that case, 220 grit will do wonderful job. If you don’t have your hand on water soluble lard oil you can use singer oil for honing.

I have made a honing tool something like this. I wrap emery paper around the front part. The slit helps to secure the paper around it.

See how the deburring and honing is done. Some says they do mirror polish. I strongly object that. My suggestion, a fine Matt finishing is needed for an airgun. 

You are done with your receiver.

In next part, will talk about the spring, piston and the seal and of-course Lubricants.

 

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Tuning HW30s or R7 Part- I Dis-assembly

After the receiver removed from the furniture these are the list of job you got to do. Just follow the Picture tutorial.

To remove the dowel pin, make sure you are using wooden hammer or plastic hammer like the one is visible in the picture.

Congratulation. You have completed a difficult task.

Next: In Part – II will discuss about what to clean.

How to Torture the Spring Guide?

The is very common in HW Spring guide. Is there anything wrong with the material? NO.

If you see closely, the material is cast Nylon 6 and the property below:

  • High modulus
  • Low stress
  • Good dimensional stability
  • Non galling
  • High fatigue resistance
  • Abrasion resistant
  • Low coefficient of friction
  • Vibration and peening resistance

But surely something is wrong with the fitment and balance between the steel ring and the guide; thus the 800 newton gives unprecedented off-axial force on the ring and you will have this result.

Good that they have used Cast Nylon . If they would have used Delrin the result could have been a disaster. Because delrin cannot take this much abuse.

Let me show you an example:

A customer purchased one of our Gamo tune kits and he decided to use a spring from a different source. He requested us to make the spring guide as per his requirement. He shared the dimension of the spring. After analysis, we had suggested what the OD of the spring guide should be. However, he wanted a much  bigger OD than that in our recommendation.

We supplied the tune kit together with  caveat that a bigger OD may cause that the guide to be tortured heavily. The customer informed us later that using bigger OD resulted in what we anticipated and warned against:

Lets see what might go wrong here.

1) Delrin is not like cast Nylon. It breaks.

2) If you see the broken part, left end, it looks like it is uprooted and it can happen only when the force acted somewhere middle of the guide heavily

This can happen only when the guide is too tight for the spring or the spring is not evenly coiled. And top of that, there is another possibility that can support this would be, the spring end was not grounded properly which led to the breakage of some part from the neck.

Anyway, the good news is: Globally we have a few hundred customers. But only one customer had this issue.

Interestingly, this customer, purchased the product on 3rd December, 2010 and after one year he came back to us and demanding for a REPLACEMENT!!

And top of that, he is kind of blackmailing by saying if we do not fulfill his demand, he will tarnish our company’s reputation.

We think, this demand is unreasonable on his part. We are sure you would find this unreasonable too.

If anyone is interested to read about his complain we found the link of the customer and here it is.

http://bsaog.co.uk/forum/index.php?PHPSESSID=b57702e19435f08df0b1fde5d119849a&topic=36073.msg316151#msg316151