My Hayabusa PCP - The Experiment Continues

[rsterne]

I spent more time over the last two days repairing machinery than making parts.... The switch on my lathe burnt out for the umpeenth time (I haven't been able to find anything that will stand up in this hick town).... My local supplier found a 12V 50A switch in stock and told me something interesting.... Apparently UL / CSA removed the AC rating on most switches a while back.... This switch used to be rated at 125V 20A, and they haven't changed the switch.... They use it on a 1 HP motor there, so I figured it can't be any worse than what I've been using.... The problem was that it was too deep to fit in the cavity on the top of the lathe, so I had to make a 3/4" deep plate with a 1/2" deep cavity so that the switch mounts 1/2" higher.... Looks kinda cool, I hope it lasts.... While I was at it I lubed, checked, and adjusted everything on the lathe as well....

The other job was to replace a broken handwheel on my horizontal bandsaw.... It's a Busy Bee Chinese special, and the handwheel that runs the clamping vice was plastic.... Needless to say, the hub split, and the only part that was reusable was the handle to spin it.... I made a new handwheel from a 1.5" cast iron pipe flange with a couple of adapters screwed into it to bush it down to smaller than the shaft.... I drilled it out, drilled and tapped it for a setscrew, and drilled and tapped a (metric) hole for the handle near the perimeter.... I works like a charm, and looks suitably "Coalmont" in nature.... I guess I've finally graduated from Hillbilly repair school....

Anyway, I finally got around to making the bolts for the two breeches, as below....



The front one with the handle screwed into it is for the .224 / .257 cal, while the rear one with the longer probe and larger diameter nose is for the .308 / 9mm.... On both bolts, the short smaller diameter nose section fits the smaller bore barrel (.22 cal on the .25 bolt, .30 cal on the .35 cal bolt), and the 60* taper is the transition to the O-ring size.... A matching taper inside the barrel guides the bullet into the chamber.... The shoulder on the bolt where the probe starts is flush with the back of the barrel port, so the chamber starts just behind the port, and the bullets have lots of length to align with the chamber before engaging the rifling.... The front driving band is just engaging the rifling as the rear of the bullet passes the front of the port, so the chamber is the length of the bullet from front driving band to base, plus the barrel port, plus about 0.030".... The O-ring that seals the bolt is captured between the end of the barrel and the breech, and the bullet slides through it on loading.... I really like this system for sealing the breech.... All the bullets are a loose fit through the O-ring except for the .257 cal, which is 0.007" bigger than the bolt at the driving bands on the bullet.... I think that will squeeze through the O-ring just fine, however....

I have ordered a set of 5C Collets and a square and hex mounting block set for them which will be really handy for making the valve and main tube.... Since they haven't arrived yet, I think my next step will be to make the chamber reamers for the .30 and .35 cal barrels and get the machining done on those.... Still a LOT to do on this project....

Bob

[SeanMP]

Those bolts look great Bob. I like the double step idea for using it on two calibers. Nice

I think your guy is feeding you a load of poop on those switches. If for some reason UL was removing AC ratings from switches I would have seen a wheelbarrow load of circulars and memos...Transport Canada and TSB are pretty serious about switches. I ordered a number of AC toggles for the ship just before I was done for the year .http://www.fastenal.com/web/products...ex?sku=0715856

But when the switch died on the UtiLathe I ordered a drum switch from Princess Auto and surface mounted it right where I wanted it...And it was dirt cheap
http://www.princessauto.com/pal/prod...versing-Switch
http://www.princessauto.com/pal/prod...versing-Switch
They have heavy ac toggles as well for under $10

You'll love the 5C set. Joe finally talked me into getting a set. I can't believe how much easier life is. Even if you only use it on your drill press the $50 for a spin is worth it's weight in gold. I use it on the mill attachment on the UtiLathe

[rsterne]

I initially drilled the .250" counterbore in the .224 barrel with a stub drill.... turned out fine, nicely centered, (I didn't go very deep) but the (118*?) shoulder was too steep and with the tightness of the chamber it was actually shaving the bullet when I pushed it in.... Soooooooo, I changed to using a center drill with a 60* taper, I had one that was 1/4" OD.... I drilled in until the taper stopped about 0.030" from the barrel port, and then polished the .250" section and the taper with 400 grit, paying particular attention to where the taper met the .224 chamber to smooth and round the edge so there was nothing to shave the bullet.... I think you might want to polish the chamber a bit more if your barrel is as tight as mine.... When I push a bullet in, it polishes the driving bands just going through the section aft of the barrel port, let alone in front of it.... It's pretty difficult to load, actually, requiring quite a lot of force to seat the bullet, especially by the time you get the base flush with the front of the barrel port.... My bolt probe is actually leaving a dent in the base of the bullet, that's how tight it is....

I was going to buy a Spin Index for the Collets, in the hope that I could mount it on my milling attachment on my lathe, but it's just too massive, so it would have been relegated to my (crappy) drill press.... I have an ex-RCAF WW2 surplus 5/8" Black and Decker "portable" drill (300 rpm fixed) mounted in a cast iron stand that converts it to a drill press.... Needless to say, any time I need any accuracy I use my milling attachment in the lathe to drill holes.... Maybe someday I'll buy a radial drill press for the bench.... What I ended up getting for the 5C Collets is a square and hex block set on eBay.... http://www.ebay.com/itm/5pc-BRAND-NE...:X:RTQ:US:1123 .... I got a set of 15 collets (1/8" - 1" by 1/16ths) from the same seller, the total was about $178 shipped, and they are on the way.... I will be able to mount the blocks on my milling attachment, so at least I can do holes at 60*, 90*, 120* and 180* from each other.... which should cover 95% of the situations.... I have a stop on one end of the milling vice now, and I'm going to put a matching one on the other end for repetitive operations....

Tomorrow the plan is to make the chambering reamers for the .308 and 357 barrels.... I was thinking of making the 60* tapered section part of the reamer, any reason why not?.... The .308 will look like the nose of the above bolt (but with a long chamber, of course.... The .357 will have the 3/8" section, but the 60* taper will be very short and then the (larger diameter) chamber.... Both will be run in so that the larger end of the taper is in the same position relative to the barrel port and breech end of the barrel.... Probably clear as mud....

Bob

[SeanMP]

I initially drilled the .250" counterbore in the .224 barrel with a stub drill.... turned out fine, nicely centered, (I didn't go very deep) but the (118*?) shoulder was too steep and with the tightness of the chamber it was actually shaving the bullet when I pushed it in.... Soooooooo, I changed to using a center drill with a 60* taper, I had one that was 1/4" OD.... I drilled in until the taper stopped about 0.030" from the barrel port, and then polished the .250" section and the taper with 400 grit, paying particular attention to where the taper met the .224 chamber to smooth and round the edge so there was nothing to shave the bullet.... I think you might want to polish the chamber a bit more if your barrel is as tight as mine.... When I push a bullet in, it polishes the driving bands just going through the section aft of the barrel port, let alone in front of it.... It's pretty difficult to load, actually, requiring quite a lot of force to seat the bullet, especially by the time you get the base flush with the front of the barrel port.... My bolt probe is actually leaving a dent in the base of the bullet, that's how tight it is....

Bob

Hmmm That's bloody odd. I actually got the chamber to the point where the bullet would drop in and settle just before it's final position. Spent hours lapping the two barrels to get them to the point shown in the other thread..........I wonder if the port work displaced at bit of metal??
But yes both barrels are gnat's arse tight.



I wouldn't hesitate to incorporate the 60* taper on the reamer. The LW QB's are done this way because of the multiple steps on the factory bolts.

I would say that 99% of everything you would ever want to do can be handled by the square and hex block. Make a sine plate for everything in between.

[rsterne]

Well mine's so tight I think I'll polish it a bit so that the bullet will slide in at least half way across the barrel port without any significant resistance.... I really have to lean on the bolt handle to seat the bullet past the port....

Might be a bit tricky mounting a sine plate in the vice on my milling attachment.... it's only 1" deep and opens to just over 2.3".... I wouldnt know how to use one anyway.... Besides, I can often turn the vise vertically and then swivel it for oddball angles.... like milling the slot for the bolt in a breech....

Bob

[rsterne]

Over the past three days I got all the machining done on the .30 and .35 cal barrels.... The first step was to machine, harden, and temper two chambering reamers, which took me basically one day.... I had made a compromise on the design of the chambers because the 9mm has both pellets and bullets to deal with (and in fact once they become available I want to try the .30 cal JSBs as well).... This resulted in the bullets being seated further forward, which would have either required a long chamber made for the bullets (and the pellets not engaging the rifling when chambered) or a short chamber made for the pellets (and the bullets would be hard to chamber).... My solution was to cut off the probe on the bolt and drill and tap the nose 8-32 and make two probes different in length by the recess in the back of the pellet, which is 0.200".... Here's what the bolt now looks like...



Now I could optimize the chamber for the bullet and the pellet would also seat against the leade by using the longer probe....The next step was to turn the breech areas to size and chamber the barrels.... I then reversed the barrel in the lathe, crowned it, and threaded the muzzle 1/2"-20 NF to accept a Hatsan air stripper.... I will have to drill out the brass stripper portion for the larger bullets, but there is lots of meat there.... Once the lathe work was done I machined the barrel ports.... Here is a photo of the machining on the barrel ends....



The main portion of the barrel that fits into the breech is 5/8" diameter, and then it's shouldered down to 1/2" where the port is.... The larger O-ring is captured between the shoulder on the barrel and the internal shoulder in the breech and is under slight compression.... The smaller O-ring is captured between the end of the barrel and the end of the breech bore, also under slight compression, and it also serves to seal on the outside of the bolt, which slides through it.... I've used this arrangement before, and I really like it.... You can vary how hard the O-ring grips the bolt by sliding the barrel back a thou or two.... The barrel port in the 9mm barrel is 0.281", nearly 80% of the bore size.... I couldn't go quite that big on the .308 but I wanted the same area, so the barrel port is oval.... It tapers from a 0.281" circle where it meets the transfer port to 0.250" wide by 0.312" long at the bore line, with the back of the port being vertical and the front angling forward at 20*.... This keeps the same area while avoiding loading problems.... The valve throat and ports will be optimized to work with the 0.281" transfer port.... Here is a photo of the two barrels, with the .35 cal (9mm) in the breech and wearing a Hatsan air stripper....



After completing the machining, I lapped both barrels with JB Bore Paste, followed by polishing with JB Bore Bright.... I checked the twist, and they are both 1 turn in 16", which is a little faster than what Lothar Walther had told me.... They told me all their airgun barrels were 450mm twist (17.7").... Both barrels are 28" long, the 9mm is 18mm OD and the .308 is 17mm OD....

Bob

[SeanMP]

Absolutely brilliant. I like your work around on the probe. Are those made of O2? I have put some thought into probes in the past but have not had the time to really work it through. I would like to see a probe that retracts back into the body of the bolt. That way I could get a much larger bearing area on the soft lead and not have flow values fall into the toilet.

Loverly job threading the muzzle!

You have now jumped so far ahead of me its not funny. Production work has taken priority on the machines again.

[rsterne]

The bolt is O1? (drill rod).... the probes are just an 8-32 bolt cut down with both ends turned to size....

Bob

[SeanMP]

Lol...yes O1.

Sloppy fingers.

[rsterne]

I got a chance to use my new 5C Collet and the square indexing block today when I made the valves.... I turned down a piece of brass stock a bit over 2" long down to 0.862" OD which is a nice slide fit in my main tube.... I drilled one end for a 9/32" throat and a 1/8" stem and the other end for a 5/16" throat and a 5/32" stem, machined grooves for the O-rings, and then mounted one end in a 7/8" collet and machined the other for the three 10-32 mounting screws and the 30* angled port, reversed it and did the other end.... Then I just cut the piece in half and faced the back end to length to allow 1/4" maximum lift on the poppet.... They are in the fully open position in this photo....



The .22/.25 cal valve (right) uses an MRod poppet, which is 0.33" OD, so it overlaps the 0.281" throat with a seat of just 0.025".... That should be nearly perfect width, and the seat is simply flat to flat.... The port is 0.250", and the throat area minus the 1/8" stem area equals that....

The .30/.35 cal valve (left) uses a Disco poppet, which is 0.43" OD and has a 5/32" stem which I have ground down to 0.120" in the portion in the throat.... I raised the seat area 0.010" so that the seat width was only 0.025" wide past the 0.312" throat.... If I had left it flat, the sealing diameter would have been larger, making the valve harder to crack.... If the seat was made flat like in the other valve, the throat could be even larger than 5/16", so a Disco poppet might even be usuable for my .45 cal / .410 shotgun version later on.... As it is, the port is 0.281", and the throat area matches that size....

I'm very pleased with the valves, the new collet and holder system makes it a lot easier to do this job accurately.... even so, it took an entire day.... The transfer port recesses in both valves are 3/8" OD and the transfer ports will be made from 3/8" Teflon rod.... The ports will be 0.219" for the .224 cal, 0.250" for the .257, and 0.281" for the .30 and .35 cal versions.... There is enough material everywhere to go to a 0.312" transfer port with a 7/16" OD for the .35 cal if required....

Bob