first "real" lathe project - new cup for SF M6 tailcap!

[wquiles]

As Andrew Wynn has posted here in the forums, he came up with a 6x17500 LiIon battery pack, but that requires a new, shorter cup inside the tailcap. He send me some dimentional data and based on that I built this working(!) prototype. Not much, but this is my very first "real" project in the mini lathe, the first time using a 4-way independent 4" chuck, the first time boring, and the first time using the tailstock with the drill chuck and center bits !!!

Here is the original (late model) SF M6 tailswitch partially dissasembled:

Here is the original cup:

and here in the left, is the new shorter cup:

here is the new cup with the original spring:

This photo shows the late model tailcap with the new cup, the late model cup, and an older model M6 tail/cup:

closeup of the late model cup vs. the older cup:

notice on the left how much deeper the spring looks when using the new cup, which of course allows Andrew's new/longer battery pack to work:

Will

 

[Lips]

Looks great.

 

[gadget_lover]

Wonderful job there, Will. Clean, properly dimensioned, well executed too.

It looks like you are well on your way to being a modder to watch out for!

Daniel

 

[PEU]

:twothumbs


Pablo

 

[CM]

OOPS Double tap.

 

[CM]

Great job!!! I've been avoiding getting a mini lathe for a few years now but it keeps coming back at me.

Will, have you seen the thread on C size Li-Ions? If you have some Alkaline C cells, can you try it out for size (mainly length) to check fit? I know a spacer is needed for the diameter but that's trivial. I think C size Li-Ions would be great for the MN21. Lastly, are you going to make these available to us?

 

[gadget_lover]

Congrats Will! Your very first solicitation for custom parts too! And on your maiden voyage no less!



Daniel

 

[wquiles]

Thank you guys

Great job!!! I've been avoiding getting a mini lathe for a few years now but it keeps coming back at me.

Will, have you seen the thread on C size Li-Ions? If you have some Alkaline C cells, can you try it out for size (mainly length) to check fit? I know a spacer is needed for the diameter but that's trivial. I think C size Li-Ions would be great for the MN21. Lastly, are you going to make these available to us?

Well, you or whomever suggested using two C size LiIons on the M6 are geniuses !!!. I just tried my two AA size LiIon inside C-size adapters, and used just plain paper to as a spacer, and guess what? My new small cup with the original spring ligthed the MN20 perfectly - simply freaking awesome !!!

To make these: Andrew Wynn owns the design, not me. If he says it is OK, then somebody would/could make these for sale. I will send a PM to him and will let him decide

As to me making them: This prototype took me about 10 hours to make, but that accounted for the time to learn to use some of the parts/operations on my mini lathe. Doind a second one would of course take much less time, but we are still looking at potentially (just a guess) of 4-5 hours. Becuase of the multi steps to make (you have to work it on both sides, so you have to re-align on the chuck), I simply can't offer these for sale yet - I would not have time and even if I would, I would have to charge way too much money for them

Lets see what happens. These new cups are PERFECT to use two C LiIons in the SF M6

Will

 

[winny]

Looks great!

Can't you eMachineShop them if it takes too long time to manufacture them yourself? Or was the entire point to machine them yourself perhaps?

 

[Ledean]

Great job . They look very well made.

 

[Lunarmodule]

Will,

Fantastic work and an answer to my prayers. I have the original tailcap mod done by Andrew for the proto rechargeable M6 project. I've been out of regular contact with Andrew lately and had the M6 on the back burner for awhile, but seeing this thread really gave me a much needed jump start on my interest in the project. I need to get back in the loop with you fellows and help finish what we started. You did such an excellent job, I suppose its way too late to send you pics or the tailcap piece itself to help out. I still have both the proto resistored packs but they are sidelined at the moment due to resistor overheating and failure. The protected C-cells in series are a novel idea, actually outperforming the 6x 17500 pack I have now in terms of capacity but there's still so much wasted space in the compartment. The MN21 works beautifully with 2 LiIons in series, provided they can deliver the 4.9A of load. I made a 6x R123 pack at first with 2.4Ah capacity, then Andrew's 3.3Ah 17500 pack. I did a series of evaluations and tests with Winny's PIR-1, which performed beautifully in terms of adhering to its programmed VBulb setpoint and allowed tremendous performance with the MN21. MN21 direct drive is much brighter and whiter than stock and with a soft start circuit and voltage clamping to limit the max voltage longevity can be built back into the design. I've instflashed 3 MN21s in the name of science just to find the outside of the envelope. Talk about your $30/second data acquisition cost! Please let me know if there's anything I can do to help you out with your current goals. I've got to reopen comm channels with Andrew again, I've just had so many real life concerns pushing my hobby interest on the back burner, seeing this thread gave me a real boost in interest in plugging my energy back into this whole deal. Look forward to hearing from you.

Cheers to you and AWR

 

[CM]

...Well, you or whomever suggested using two C size LiIons on the M6 are geniuses !!!. I just tried my two AA size LiIon inside C-size adapters, and used just plain paper to as a spacer, and guess what? My new small cup with the original spring ligthed the MN20 perfectly - simply freaking awesome !!!

To make these: Andrew Wynn owns the design, not me. If he says it is OK, then somebody would/could make these for sale. I will send a PM to him and will let him decide

As to me making them: This prototype took me about 10 hours to make, but that accounted for the time to learn to use some of the parts/operations on my mini lathe. Doind a second one would of course take much less time, but we are still looking at potentially (just a guess) of 4-5 hours. Becuase of the multi steps to make (you have to work it on both sides, so you have to re-align on the chuck), I simply can't offer these for sale yet - I would not have time and even if I would, I would have to charge way too much money for them

Lets see what happens. These new cups are PERFECT to use two C LiIons in the SF M6

Will

The idea of C size came to me when AW posted his feeler here :http://candlepowerforums.com/vb/showthread.php?t=106075&page=1&pp=30
I probably can't take credit for the idea since it seems so obvious (at least to anyone who has been looking for years for a rechargeable SF M6)

Will, I understand the reluctance to make these due to the time involved. However, I'm not willing to let this thing die, at least not for myself, hehe. You guys did a nice job of presenting options so the individual modder has someplace to start :thumbsup:

Oh, to add to the C size idea, I just tried D cells and it's almost a perfect fit diameter wise. However, length makes it a no go but an extended tailcap assembly will make it a go. Hint hint...

EDITED: I really need to make room in my garage for a mini-lathe. But my reloading equipment will not take kindly to a lathe infringing on their space

 

[Lunarmodule]

Will,

Another note, the D LiIons ARE possible, with 2 variations: either fabricating a small extension tube (I'm going to ask Tranquility Base about this at present) or going to a completely external switch assembly and engaging only 2 threads of the existing tailcap setup. Obviously option 1 is preferred but option 2 at least gives it a promising nod. Its only 25mm more length than a 2x C-cell or 2s3p 17500 pack would require. The extension tube would be ideal to allow an additional 10mm for a Hotdriver or PIR regulator, and a perfect logical location for it as well. Just like Andrew's justification of modding the cup inside the tailcap: "If I can almost double my runtime by spending 5 minutes modding the tailcap with a Dremel, then its 5 minutes spent with the Dremel". If seriously increasing runtime and making a nice comfy home for a regulator circuit justifies fabricating an extension tube, then it should be explored. As beautiful as your finished work is, I believe it would be far simpler to add 45mm in length via an inside/out threaded tube to effectively lengthen the stock battery chamber and negate having to change the stock SF part at all. The added bonus is of course complete reversibility. The C-cells are a great choice, but for no-holds barred performance, max runtime, the leap from 3,300mAh to 5,200mAh (but sacrificing cell protection, not a minor issue) holds promise indeed. From experience I know 3Ah eclipses stock runtimes noticeably, so the pair of C-cells should give about 35mins continuous MN21 runtime easily. This could stretch to 50,55, or more minutes with the D monsters on board with an extension tube. Nearly an hour of soft start regulated MN21 light on a single charge? Dont wake me up, I'm not far from NOT dreaming about it. I'll ask Andrew about it, but Id fall over backwards to put your proto piece to work. I'm probably send my unmodded M6 back to Andrew to finish regulator implementation, and your tailcap part is a key component. Here's a pic of Andrew's Dremel work:

 

[CM]

Keep it coming guys :thumbsup: I like the idea of lengthening the tube for the reversibility. I can see all the mods this is going to spin off on the M@gs if D size cells get mainstream use.

 

[wquiles]

Thank you guys . While I worked on the new cup I never realized it would touch such a strong nerve with SF M6 users :rock:

I really love the idea of the small extension tube - brilliant. I have an Al tube with OD of 1.750" and ID of 1.250", and since the OD of the SF M6 tailcap is about 1.748"" or so, I should be able to work on a prototype spacer for the M6 in the right diameter. The only "problem" is that I have not yet learned how to do threads on the mini-lathe - which is my next learning experience

Will

 

[cy]

most excellent mod!

sure glad I snagged a spare M6 tailcap

 

[CM]

most excellent mod!

sure glad I snagged a spare M6 tailcap

Lucky dog you. I'm looking at my M6 tail cap right now with bad intent. Must stay away from Dremel tool, must stay away...

 

[Lunarmodule]

Will,

You are doing M6 owners everywhere a great service by taking on the cup alone as a "learning project". My hat is off to you, sir! Very nice workmanship. While I had the beta version of the PIR-1 for testing I tried a few mock ups for various rechargeable battery configs that would also mount a regulator of some type. The D cell LiIons are a perfect fit in diameter for the M6 batt compartment and even can engage a few turns of the threads of the stock tailcap with the switch removed. I stared at the setup for some time and concluded since the stock tube is threaded on the outside, an extension tube with inner threads is a natural for getting that extra 20mm for the battery and a spring and might as well throw in another 10-15mm for a regulator circuit. Makes for a nice modular reversible M6. Add tube and 2x D Lion pack for MONDO regulated runtime. I like the sound of that. If you feel so inclined to make up a proto, I'm offering any help I can provide, just let me know what you need, send me an email or PM.

Regards,

Steve

 

[gadget_lover]

Will stated earlier that turning the cap was labor intensive. Should we discuss (in this thread) ways to plan the machining to minimize tool changes and remounting parts to facilitate a run of these?

It's Will's thread, so maybe a seperate thread on planning machinging steps is more approriate. If there is interest I'll be glad to throw in my 2 cents.

It's neat to see another new machinist join the frey with new ideas and perspectives. Again, good work Will!

Daniel

 

[wquiles]

Daniel,

It was labor intensive for me, but I am just a beguiner. I am sure you and other more experienced could make this in less time

At any rate, feel free to discuss any/all regarding making this cup

Will