Bulldog .250 needed an MDS hammer w/adjustable striker

[mackeral5]

I wanted to share a somewhat recent collaboration with a couple of GTA members. 

Some time ago I crudely carved out an MDS hammer for my Bulldog, as a working prototype, proof of concept type of project.  Initial results were promising so I decided to reach out to a couple of GTA members to see if they were interested in helping me take the crude prototype to a more refined, documented design, and make a couple using lessons learned from the prototype. 

One member provided design support and developed the drawings/models.  This included solving many details that were not part of my crude prototyping process such as angles, tolerances, defining the fabrication/assembly operations and sequences. 

A second member provided additional refinement of the fabrication/assembly process as well as the actual fabrication and assembly of components. 

My collaborators possess much greater skills than I, especially in the areas of attention to detail and precision.  You will see that here when comparing the prototype to final design and execution. 

Here are a few pics. 

Various bulldog hammers.  Skeletonized 46gram OEM far left, middle OEM with peek striker, right my prototype MDS with brass core and peek striker



The prototype was very light, right around 30 grams.  Required too much hammer spring, even with my simplified balanced valve.  But results were favorable enough to warrant further development.

A sampling of the documented design.



The prototype next to the final versions.







We created 2 different brass core designs.  The one with the smaller diameter hollow is the one I mainly use, it is designed to be compatible with my guide fixed at the rear SSG.  The brass core with the larger diameter hollow is compatible with an OEM hammer spring configuration.

Both hammer designs weigh in the 40-50 gram range and are not necessarily suitable for an OEM unregulated bulldog.  However for my balanced valve equipped smallbore .250 bulldog they are a perfect match.  The adjustable peek striker was a game changer from a tuning perspective.  It took a while to find a good combination of balanced chamber volume, HST, and striker protrusion.  I am still learning how those adjustments all interact.  I added a buffer system that functions like a bstaley mod, but doesn't rely on Oring's staying put.  I do not have pics of that but it works very well so far and there is no concern about orings moving around.  The Bulldog has a valve body retention nut, I drilled 6-8 holes and glued in sections of 90 duro  Oring, like bristles protruding 1/16 from the valve nut's face, stopping the hammer's forward travel.  I hope that makes sense to those familiar with a Bulldog's inner workings...  At some point I will try to get a pic of this area. 


All in all I could not be happier with the collaboration.  3 similar minded individuals living far from each other, who have never met nor heard each other's voices were able to achieve a desired outcome.  All communication via emails and pm's, each contributing their time and expertise, and the end result actually working as intended.  The journey was very rewarding, I appreciate the process equally or more so than the final output, the hammers themselves. 

[subscriber]

Nifty!

[bear air]

Great work Mike.

[mackeral5]

Great work Mike.

Thanks Chris. The idea/concept was the easy part.  I was lucky enough to have a couple of very talented who were willing to help make it a reality.  Hopefully they found it as gratifying of an experience as I did. 

Being able to limit hammer-influenced valve lift (there is probably a better term for this) is a very cool adjustment to have, none of my other guns have ever been equipped with this feature. 

[sb327]

This kind of collaboration stuff makes me happy. I’ve been working on a prototype valve and have been collaborating with another to achieve a certain goal.

Excellent work and thank you to those who participated. THIS is what moves our hobby forward.

Fwiw, I just moved my hammer weight from 11.5ish to 7.7grams. I haven’t got to try it yet. Fingers crossed I get a pretty wide tuneable range.

Dave

[luge007]

Mike,
You are very welcome. I was happy to help out with the machining of those hammers, as well as enjoying the whole collaboration process.  Of course the flawless drawings you provided via e-mail could have been sent to any machinist to be made, being able to keep the project within the GTA community just made it that much more gratifying.  I was also very pleased to see the custom parts for your "little .357 Blaster" project worked out so well.  It's always enjoyable for me to see the finished product assembled and working as it should, meeting or exceeding expectations.  I'm already looking forward to working with you on your next project.


M

[subscriber]

Nice machine work you did there, Matt!

[luge007]

Thank You for the compliment.


 Now that 'the cat's out of the bag' so to speak, I'll elaborate on the project a bit.


 This composite hammer turned out to be tricker than meets the eye.  Not difficult, just different.  The odd 65 degree chamfer, could have been done with the compound on the lathe, but I chose to make a dedicated chamfer tool ground out of HHS.  I very much dislike messing with a perfect compound adjustment when multiple parts are required, preferring to make each complete part in one setup if possible. That and I just wanted to play with my 'new to me' Baldor grinder.   Also my first experiance with PEEK, cutting 28tpi threads into the 'PEEK strikers' turned out to be a learning experience, requiring a few more spring passes than metal.  Cutting the screw driver slot as specified in the plan was no real challange with the right slitting saw in the mill, but it did require setting up a collet block to hold them and indicating in each of the 'screws'.  Yeah, I probably could have used a Dremal tool or hacksaw for a 'close enough slot', but that's not how I roll with paying clients.   The brass cores were fun and easy to make, though did require a particularly small boring bar to get the radiused edge, square bottom hole as specified on the print.  I bonded them into the MDS 'jackets' with bearing retainer, then did the final drill and tap for the grub screws and made the 'mechanism relief cut' on the mill.  Also had to replace the 65degree chamfer that the mill took off in the 'relief cut'.   I could have probably 'cheated' in several areas where dimensions were not critical, but not knowing the full extent of the project, I built the parts EXACTLY to print.


The light work that went into those compsite hammers would have been a nice 'warm up' to making Mike's previously requested, custom, steel, 8", Gen 1 Marauder 'tube' from scratch on my MANUAL mill....... that was a real challange!  Not sure I would do that again, because nobody would pay for what the machine time was worth.  It would have been MUCH easier to shorten a factory tube, or find another machinist with a CNC Mill with a 4th axis to machine the part.  I pretty much accepted the job as a challange.  Single point threading the tube for the aircap, pfffffft, easy, making all the holes, milled slots and off center tapped holes, all at precise 90 degree increments, and as in the case of the valve screw holes, in perfect alignment with eachother within a half a thousandth?  Yeah, that was a bit tricky, and took a really long time to make absolutely positive everything was as the Crosman/Benjamin Engineers designed (going from an original tube that I meticulously blueprinted).  Also the required jig, while not difficult to make, was nessessary to complete the build.  An internal, 6 petal expanding arbor, with a machined, squared end to indicate from.  The rest of the setup was pretty straight forward, though I did have to order a few diameter specific endmills for the job.  The internal jig also allowed me to cut the features all the way to the end of the tube, where an external collet or rotary table and chuck would have been in the way.  I wasn't keeping very careful track of time, but it did pretty much take all of Superbowl 56 game time. (lol, no I'm not a football fan)  Anyway, that project worked out very well and as always, I'm happy to have helped out a fellow Airgunner and GTA member.


M

[subscriber]

Matt,

I think this, like so many jobs should have the designer ask the machinist how they would machine each feature.  Specifically about their capability, and what detail changes the machinist would like to make the job easier.  Obviously, the customer's functional needs should remain paramount.

The size of fillet radii for example are negotiable.  Large enough to be useful, and not fouling the mating part are what is required; rather than "to print", to the nearest 0.001".

I thought this design job would be tricky, but it was very simple, compared to the offset muffler.

[luge007]

Peter,
Did I just mis-read your post "I thought this design job would be tricky, but it was very simple, compared to the offset muffler."or did you just take (well deserved) credit for the hammer and offset LDC CAD work for Mike???  IF so, I suspected your skills may have leant a helping hand.  Greatly appreciated.  It made my life a bit easier than working from PM descriptions,  'napkin sketches' and crude, dimensioned pencil drawings.   YES, I CAN work from those, but there is a LOT of back and forth with the PM's to clarify exactly what the client wants.  I completley hear you about working WITH the client and clarifying areas of critical dimensions and those that are not, but in this case I chose to minimize influence as to not alter the outrcome in any way, the directions were very specific.  That and IF I "work to print, I can never be wrong" . 

Most of the work I have come into the shop has been simple cut-down and re-thread of airtubes as well as, cut-down, thread and crowning of barrels, those do not require a blueprint, just the mating parts to be fitted if there are any.  There have been a few very interesting jobs thrown in the mix to keep me on my toes and busy on the machinery that did require multi-page, detailed drawings.  They are fun (for me).

Cheers,
M

[subscriber]

Matt,

I can't take credit for the hammer design.  Mike pretty much specified what he wanted.  I translated that into dimensioned Solidworks models.  I suggested changes that would simplify machining.  For instance, many hammers have a groove cut in them; as did Mike's initial design.  As the groove in this instance was not an anti rotation feature, and no significant bearing surface would be lost, I suggested a flat clearance cut all the way across the hammer to simplify machining.

Initially I had a sharp bottom corner inside the brass weight bores, because I figured you would have a tool with a radius ground into the tip, and I did not want to drive a spec that was flexible.  Mike asked about that fillet, so I added it to the models, with notes about how much it could vary.

Mike wanted a certain mass to the hammers, and by specifying materials for the parts in Solidworks, I could read the predicted combined mass of the hammers.

With the offset muffler, Mike specified the space constraints, and I made proposals; that he then approved. So, my design in that instance, approved by Mike; then assembled by Mike from parts printed by GTA member TorqueMaster.  As Mike had used his .357 blaster at 200 FPE previously, that is what I designed the offset muffler for.  It is a bit bulky for 100 FPE, but certainly takes the edge off the report.

Mike has several other mufflers that I designed, that he may or may not report on.  This includes another reflex design.  Also, replacement guts for a DonnyFL that had been damaged by a double loading event (if I remember correctly).  In the latter instance, the internals have no resemblance to the original parts, except for their interface dimensions to match the original outer tube and endcap.

[luge007]

Peter,
Mike starting off with a solid understanding of what he wanted, combined your brilliant CAD work and working knowledge of how parts are machined which worked out very well for me, I just put tool to material.  For sure, working WITH the 'client' as it were to get the end result through a dialog is key in colaborative design work.  In some cases I may not fully understand what some of the parts I have machined are, or do, but I can read a detailed print and make them to spec.  Other times I fully understand what the client is trying to do, yet their not sure how to go about it or makes poor material choices, then I get to 'guide' them towards their goal.


Not sure about posting the details on the 'replacement DonnyFL guts' in this thread, but it is of great interest to me if you wouldn't mind sending me details.
Cheers,
M

[subscriber]

Matt,

I emailed you the details to you freediver account.

[JuryRigger]

Nice work! 
A deceptively simple part; done quite magnificently!...
The collaborations really are the spirit of the GTA IMO; just a bunch of folks who love airguns hitting the next level 
Jesse

[Motorhead]

Ah the memories of my M-rod LW hammer development R&D some 10 years ago.

GREAT JOB by all involved in this project