Making springs for NRVs

Greetings Gents,
Thought I would share this even though I'm 1/2 done what I set out to do.

I have run into a number of Swedish NRVs that have an oddball spring in them and it's a shame to swipe a spring from the spare (and new) NRVs that I purchased from a member here a while ago. I've also run into a number of NRVs in my fettling with the little black seal device. I prefer the brass bucket or piston type seal carrier, and likewise don't want to swipe parts from perfectly good NRVs to solve that issue.

So..........
I measured some good springs and came up with .016 inch diameter brass spring wire as the material, and needed an ID on the spring of .145 inch, with a length around .5 inch.
I purchased a 75 foot coil of the spring wire from a firm as per the link here for $10. They sell kits, parts and such for dulcimers and other stringed instruments. www.fortepiano.com

After some experiments I learned that the form to wind the wire on must be .83 of the ID you want for the spring so it came out to .120 inch (3mm). I found a gage pin that diameter and put it in a drill chuck mounted in my lathe, but I think you could do this with a hand drill if it were clamped firmly to the work bench. I am turning mine by hand and the hand drill would probably have to be turned by hand as well.

The brass spring wire arrived as a coil so I wound the wire onto a plastic spool that used to have fishing line on it with a rubber band over the wire to keep it in place. The spool helps in keeping a good tension on the wire when feeding. I bent a 1/4 inch or so dog leg at 90 degrees on the end of the wire.



The dogleg gets pushed into the chuck along side one of the jaws. Then turning it by hand I put on 3 turns side by side then made a helix up the rod to a mark I put on at 1/2 inch, and made 3 more side by side turns. When done it slides easily off the rod.



After some trimming with small wire cutters it looks like this. My eyes are bad so I used a microscope, but an eye loupe (or better eyes) would work. A little tweaking was required with tweezers but after making 3 of them or so they come out better, and the tweaking is less and all in all it gets a bit easier with some practice. I put one of the black rubber type seals (which I don't like, and can't repair) in the photo for reference.



I have recently ordered brass rod that has now arrived and plan to next set up and turn a bunch of the seal pistons (buckets?) and will then be able to put a nitrile disk in any NRV I work on that needs it. This will take a while but I will post on the success or failure later on.

Best Regards,
Doug

 

Hey Doug do you need help i was a lath operator mill right radio drill maintenance man engineer inventor on some machine that could not wait weeks for a new part we made it there. At times i work around the clock after the other guys did there ting then do the machineing.

 

Hi Robert,
You're up late.

Well just the other day Marlene said " Doug , you need help ". I don't think she meant the same thing. She's probably right though.

I didn't know you worked on lathes Robert. It's good to know, and you know I'm just
messing around in the garage having a good old time. I have a bunch of NRVs in a little container now that needed help so I thought I would try the springs. They were easier than I thought. The pistons (buckets) will be a little time in set up 'cause I plan to run off a bunch of them right off bar stock in one setup without secondary cutting (hopefully) except maybe a file to take off the cut off burr. If it goes right I will make about 50 or more, especially if anyone else needs them. Not sure of the demand for them, we'll see.
Regards,
Doug

 

Yep just make them buckets that they take the rubber with no tip .You know the hardest thing to do with a lath is the first and last step so as whats left can be still held in the lath takes some thinking before you start.Do i drill fist or do i shape it do i do front side first or do back or the outside etc.Same on a milling machine how much of a cut .I have taking of .050 at a time on cold roll steel fast rpm slow cross speed blue hot chips wow on lath on plastic and bass cross as fast as it can go.Some things take all that looks simple.Now boring bar that somthing with a lath you got to be part of it or it bite you got to now all the back lash etc and by the sound it make i can tell when some mess with mine i always leve it so so.

 

Hi Doug, You have done another great job in designing and manufacturing spares for classic stoves. Well Done!
I would certainly like to put my name down for a few brass cup, washer-carriers, for NRVs.
I hate those plastic abortions that were fitted to some of the later stoves. I had the misfortune to have to replace one when fettling one of Ian's Primus 210s at Newark this year.

Best Regards,
George.

 

Misfortune?
Nay.
Think of it as an enhancement of the stove world in general and a 1935 self-polishing 210 in particular, and bask in the warm glow of virtue.

 

Genius, pure bloody Genius !!

I was just preparing a thread on this very subject, my 2 recently arrived stoves have one good NRV between them.

Put my name in the order book.

You are the Man !!

 

Great stuff Doug, but for those of us with less talent, you could try giving the existing spring a gentle stretch to reinvigorate it, it's worked for me. Gently mind they do go brittle with age, like the rest of us.

I would think that as the pressure in the tank effectively closes the NRV the condition of the nitrile seal should be the first port of call when fettling it.

 

Hello,
Help, help? Doug you are a madman when it comes to figuring this stuff out.

You should see him in action! All these handmade milled pieces that make this and that.

Doug let me know when you have things for sale. I am interested in aquiring some of your well made items.

Chuck

 

I don't think that running off 50 will be enough Doug!



CB

 

Thanks all,
Keith- I am fixing: wrong spring, no spring, and cut in half and stretched to the limit springs that others tried as a fix which I found in surprise in NRVs. Surprise ! Also the black nub seals that George mentioned, I had one at High Point so this is a bucket and spring manufacturing effort to solve both issues. I have a lot of NRV parts in a tin waiting for the items I'm attempting to make.

Robert, my lathe is like a manually operated screw machine so it is not automatic but a lot of tools can all be set up with stops to get a somewhat fast production time per part. I am hoping to run the buckets in a one pass off the machine so I won't need to do any secondary operations (For non-lathe users: turning the part around, and reinstalling in a lathe a second time for additonal cutting) which usually affects concentricity a little. The small size of the bucket means I should pay extra attention to this detail of concentricity or I will have opened the door for trouble so I will eliminate secondary, essentially eliminating that issue. The less trouble the better. I will post a photo for you Robert as you may appreciate the setup, and I am hoping to have the parts coming off the machine at a good clip. I will have a cutoff burr to remove and hand file for removal on each piece on the small diameter end as it is parted off the bar stock it is machined from but that is all.

This is the present part drawing for the bucket, which may still get a revision for fit of the springs over the small diameter if necessary.




I will post again with the results of startup of bucket production, and will run off as many as I can from a 6 foot barstock of .218 inch diameter brass.

Thanks for your kind words and support.
Regards,
Doug

 

Hi Doug

Oh indeed, and I know that your versions will be wonderful ! I was just trying to caution against blaming the spring when in most cases it's just the nitrile seal that needs replacing.

I also much prefer the buckets for the seals so will be in the queue when production starts !

Cheers

 

Doug here a hint get a sewing machine motor with foot peddle for speed put a drill chuck on that make springs

 

Hi Gents,
It would have to turn awfully slow Robert. I found it much easier to just turn by hand, and I think you could do it by turning the spindle of your hand drill if it were solidly moutned so both your hands are free.

Keith, by all means the nitrile is first, but when no spring is present or a steel impostor spring is present in the NRV scratching up the bore of the cylinder it resides in, then nitrile and the spring are both at issue.
I will put some pics on later, you have to see these.

Regards,
Doug

 

Hello,
After removal of a number of NRVs you may find a few with strange innards. Mostly I find good springs but here are some odd ones labeled junque, and there have been others which I have already tossed out:



Regards,
Doug

 

Hi Doug

Your springs and cups are absolutely amazing.
Can you easily make more than 50? I am sure the demand will be large. Certainly put me down for some - please!

 

The way read it you have a hole in a bar on the saddle and use your screw to get the pitch right. the hole in the bar to get the tesnsion.
Well theroy that is.
How they make em in the good ol days.
Cup
Only need to make a parting off tool to get the smaller diameter and then part off.
If you have a step or just move the saddle a tad you will be only left with a tit on the centre.
no clean up required.

Could do with some me self.
Seem to be gettting a lot of those nitrile all in ones and have ran out of cups and springs.

Was thinking of trying a primer cap or something to see if it fits.

Will find a machine one day.
Must start looking again.

Cheers
Barra

 

Must find a machine again.

Barra do an ebay search of Atlas or Logan or Craftsman lathe. should turn up hundreds


lance

 

Hi Gents,
Midnight is closing in on me, so I'm done for the evening but I have cut a few parts and done just a little testing. The results are good, the setup had some minor stumbling blocks but it's going to run ok.
This is the first good one.




You might need to review the drawing here:

Now upon review of the cylinder that screws onto the NRV body (as in the photo above), and a test fit, I will need to add a chamfer to the outside corner of the bucket body at both ends but in particular at the disk end as it hangs up on the threads or maybe the bleed holes when sliding inside an NRV cylinder. Will do that tomorrow and test on all the cylinders I have on hand (which are from various manufacturers and may vary) just to be sure it has improved.

The chamfer on the tail end where the spring is installed needs to be longer, because it cants the spring to one side in off axis fashion, and this is probably part of the trouble with the corners catching as mentioned above. Will experiment with that as well, and may end up reducing the diameter of the tail a bit if the tail chamfer lengthening doesn't cure the spirng alignment problem .

When it's all set up I will get a photo of the machine with a part in process. I might get 150 parts or so from the stock on hand. Will know more tomorrow.

Regards, and thanks for the support,
Doug

 

Doug, all the NRV's that i have, have that bit of a cant to the bucket too. I wouldn't worry too much about it but the camfer on the ends seems a good idea if it doesn't take too long for the resets of the stock.

lance