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



## wquiles (Mar 4, 2006)

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


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## Lips (Mar 4, 2006)

Looks great.


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## gadget_lover (Mar 4, 2006)

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


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## PEU (Mar 4, 2006)

:twothumbs 


Pablo


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## CM (Mar 4, 2006)

OOPS Double tap.


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## CM (Mar 4, 2006)

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?


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## gadget_lover (Mar 4, 2006)

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



Daniel


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## wquiles (Mar 4, 2006)

Thank you guys 




CM said:


> 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


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## winny (Mar 4, 2006)

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?


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## Ledean (Mar 4, 2006)

Great job . They look very well made.


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## Lunarmodule (Mar 5, 2006)

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


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## CM (Mar 5, 2006)

wquiles said:


> ...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
> 
> ...


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


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## Lunarmodule (Mar 5, 2006)

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:


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## CM (Mar 5, 2006)

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 [email protected] if D size cells get mainstream use.


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## wquiles (Mar 5, 2006)

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


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## cy (Mar 5, 2006)

most excellent mod!

sure glad I snagged a spare M6 tailcap


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## CM (Mar 5, 2006)

cy said:


> 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...


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## Lunarmodule (Mar 5, 2006)

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


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## gadget_lover (Mar 5, 2006)

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


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## wquiles (Mar 5, 2006)

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


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## gadget_lover (Mar 6, 2006)

Ahhh, Open license to hear myself talk! cool!

As far as I can see, a piece like this can be created without taking it out of the chuck. When I tackle a task like this, I write out the steps before doing it the second time. The written list of steps makes it easier to make sure it's done right. It also helps highlight points in the process where you want to change the order to minimize tool changes or remounting the work.

In general.....

Cut stock to the finished size you need plus enough to hold it and provide tool clearance. I add about an inch, maybe inch and a half. I cut crooked, so I leave an extra 1/4 inch to allow for waste when facing. You can use this face as the reference for all your cuts and boring.

This piece has a center hole (for a screw?) and a slightly shallower, wider hole for the spring. It also has a wide bore and a turned shoulder. It's a good idea to drill the inner hole first, followed by the next and then boring the recess. If the center hole is really, really small, drill the second hole to depth first and then drill the smaller diameter hole.

Once that is done, you can start on the outside turning. Reduce the diameter to your spec first. Then turn that lip on the right hand side to leave the ring. The right hand side is easy, simply using a tool that cuts to a left hand shoulder.

The big post on the left side takes a tool that cuts to a right hand shoulder. It looks like it's about 1/4 to 1/2 inch. You waste a bit of metal, but it works well if you simply make that about 3/4 inch long (or more) to give you room to move the tool left and right. Use a parting blade to remove the piece at the exact length that your plans call for. Clean the cut off end up with a file or sandpaper if necessary.

Note that the piece was mounted only once. All end work was done before reducing the diameter so that you have maximum stiffness when boring and drilling.

The whole process calls for 1 boring bar, 1 or 2 drills (since the spring recess could be bored), a left and right hand tool and a parting tool.

The only tricky part is cleanly measuring the depth of the drilled holes. with a Cummins 7x12 lathe. The graduations on the tailstock quill are pretty coarse. I usually double check with a caliper.

Daniel


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## HarryN (Mar 6, 2006)

How close would a 2 ohm or 10 ohm resistor be to fitting your needs to tame the cells down a tad ? I just happen to have some that might work, if you can solder 1206 size. These are not your father's resistors, if you know what I mean.  

I think that lamp is only 4 or 5 amps, so they can handle the power, no problem.


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## wquiles (Mar 6, 2006)

HarryN said:


> How close would a 2 ohm or 10 ohm resistor be to fitting your needs to tame the cells down a tad ? I just happen to have some that might work, if you can solder 1206 size. These are not your father's resistors, if you know what I mean.
> 
> I think that lamp is only 4 or 5 amps, so they can handle the power, no problem.


I don't follow. You meant to say to use a resistor instead of a regulator for a particular battery/lamp combo?

Will


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## wquiles (Mar 6, 2006)

gadget_lover said:


> The whole process calls for 1 boring bar, 1 or 2 drills (since the spring recess could be bored), a left and right hand tool and a parting tool.
> 
> The only tricky part is cleanly measuring the depth of the drilled holes. with a Cummins 7x12 lathe. The graduations on the tailstock quill are pretty coarse. I usually double check with a caliper.
> 
> Daniel


Awesome - you are right. It "can" be done in one long operation !!! :rock: 

Yes, measuring the hole depth was tricky. I used tape on the drill bit to mark how far to go 

Will

PS. This is my post # 2000 !!!


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## CM (Mar 6, 2006)

HarryN said:


> How close would a 2 ohm or 10 ohm resistor be to fitting your needs to tame the cells down a tad ? I just happen to have some that might work, if you can solder 1206 size. These are not your father's resistors, if you know what I mean.
> 
> I think that lamp is only 4 or 5 amps, so they can handle the power, no problem.



Why would you want resistance? Those 1206's will fry like an egg--no way can they handle the power. Even at 2.5A, the two ohms resistor will drop five volts and dissipate 12.5 watts. If anything you want to minimize any path resistance.


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## HarryN (Mar 6, 2006)

Post 11 - Lunarmodule discusses a pack he tried to make with resistors, but they burned out. Of course, the PIR is better if you have one.

CM - normally, you would be right about the ability to handle power. Like I said, these are not your father's resistors. They do require the heat to be removed, which is it own challenge, but it is within the rating.


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## KC2IXE (Mar 6, 2006)

gadget_lover said:


> ...snip...
> Note that the piece was mounted only once. All end work was done before reducing the diameter so that you have maximum stiffness when boring and drilling.
> 
> ...snip....



The thing I see "Missing" on the new cup, that MIGHT not make any difference, and ALMOST requires a rechuck - if you look at the original cup, there is a countersink on the center hole on the back side - Yeah, there ARE specialty tools for back spotting/counterboring/countersinking, but unless you are doing serious production work, it's probably better to either leave it off, or reverse the part for a second operation

IF you have to reverse for the second operation, then doing the rear spigot in the second operation makes sense - ditto the groove in the spigot (also left off)

This is the type of work that IF you have a lathe with the correct collet sizes, you can do the job so easily....

IF you can leave off the back countersink - your method works just about perfectly - Now, let's think about how I would do it if I could NOT leave off that countersink....

FIRST - face the backside

2 - drill/countersink the center hole (hint - if it's production - countersink FIRST, as it'll act as your center drill at the same time...)

3 - turn rear spigot, turn groove

4- turn outer major diameter

5- part off work piece (assuming you are working "thru hole" on the headstock) - otherwise, - eliminate step 4 - add step 0 of cutting blank to rough length

6 - reverse part in lathe - grip by spigot - preferable in a collet - possibly in a pot collet if oversized

7 - face to length

8 - turn to outside diameter (if not done in step 4 - see step 5 note)

9 - put in o-ring groove (if desired)

10 - turn/bore recess in cup

Done

In production, you would do all the parts for the first chucking first, then do all the second - of course, you'd probably use CNC with a live right hand side, or a screw machine with a live right - so you can do the spigot side, grab the part - retract, machine the other side - while holding the part on the other side - depending on production run count


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## CM (Mar 6, 2006)

HarryN said:


> Post 11 - Lunarmodule discusses a pack he tried to make with resistors, but they burned out. Of course, the PIR is better if you have one.
> 
> CM - normally, you would be right about the ability to handle power. Like I said, these are not your father's resistors. They do require the heat to be removed, which is it own challenge, but it is within the rating.



Sounds like we're talking about different things. I thought you were saying to add series resistance in which case 1206 would not work. I'm not sure what the details of the circuit is in Post 11 but 1206 resistors are rated 0.25W if that helps. I'm guessing the circuit is a soft start circuit????


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## HarryN (Mar 6, 2006)

Hi CM, I think we actually are talking about the same thing, but feel free to correct my misunderstandings.

Li Ion cells, 18650 / C / D, pretty much all hit 4 - 4.2 volts fully charged, and approx 3.7 V MPV IIRC. Two of these in series will peak approx 8.4 V and MPV approx 7.4 V. They are also capable of discharge currents sufficient to support M6 bulbs. 

The HOLA bulb for the M6 is nominally driven at 6.8 V, at least using some info posted by JS in his R M6 threads. To my simple mind, that means "hot off the charger" excess voltage of 8.4 - 6.8 = 1.6 volts, and MPV excess of 7.4-6.8 = .6 volts, so an average of around 1 - 1.2 volts "excess", at nominally 5 amps desired lamp current.

This excess can be dealt with by a) True DC - DC regulator b) Intelligent PWM switcher (Winny) c) LDO (AWR) or d) A power resistor capable of dissipating that much power. (approx 5 amps x 5 amps x 1 ohm) = 25 watts.

While not necessarily desireable, this power could be dumped to a resistor, certainly heat sinking would be critical.

You are correct that "normal" 1206 resistors are designed for 1/8 - 1/4 watt. The ones I have are not. Kind of mind blowing, isn't it ? :naughty:


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## gadget_lover (Mar 6, 2006)

kc2ixe said:


> The thing I see "Missing" on the new cup, that MIGHT not make any difference, and ALMOST requires a rechuck - if you look at the original cup, there is a countersink on the center hole on the back side - Yeah, there ARE specialty tools for back spotting/counterboring/countersinking, but unless you are doing serious production work, it's probably better to either leave it off, or reverse the part for a second operation



Thanks for a look into the possibilities with a production setup. You bring up a good point, and that is the idea that your process has to match your tools. A collet with feed-through will allow for a different process than an independent 4 jaw chuck, for instance.

For the home shop, there are sometimes details that lend themselves to being done by hand. If I were Will and decided to add that countersink, I'd most likely use a hand held drill (assuming the dimensions are not critical) with a countersink bit.

Daniel


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## wquiles (Mar 6, 2006)

KC2IXE said:


> ... if you look at the original cup, there is a countersink on the center hole on the back side ...


So far neither Andrew nor I can think of any real/practical value for that special neck, so it was left off. It does not affect functioning at all in my M6 

As to the holes, they should all have a light counterbore/shoulder, but that could be done even by hand as it is not that critical 

Will


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## KC2IXE (Mar 6, 2006)

gadget_lover said:


> ...snip.... You bring up a good point, and that is the idea that your process has to match your tools. A collet with feed-through will allow for a different process than an independent 4 jaw chuck, for instance.



Sure does - and a Pot chuck will give you capacity greater than the feed through of the lathe - you bore them out to fit the work - I sould probably document how I make the battery adaptors I make for the guy at

http://www.k3camera.com/k3/k3batt.stm

I've probably made 3-400 of them by now - in my HOME shop. I do wish my lathe had a through bore > 5/8" with the lever collet closer in place. I keep thinking about a new lathe, but the budget is not there - and I have WAY too much tooling for my existing lathe




gadget_lover said:


> For the home shop, there are sometimes details that lend themselves to being done by hand. If I were Will and decided to add that countersink, I'd most likely use a hand held drill (assuming the dimensions are not critical) with a countersink bit.
> 
> Daniel



Doing things by hand does work VERY well in low production setups.

I would LOVE to afford something like an Omniturn Jr - or a retrofit of an OmniTurn slide and air closer for a Hardinge - running off 100 adaptors at a time then would be trivial - of course, that's WAY out of the "Hobby" budget class - if you do that, you better start looking for paying work


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## CM (Mar 6, 2006)

HarryN said:


> ...This excess can be dealt with by a) True DC - DC regulator b) Intelligent PWM switcher (Winny) c) LDO (AWR) or d) A power resistor capable of dissipating that much power. (approx 5 amps x 5 amps x 1 ohm) = 25 watts.
> 
> While not necessarily desireable, this power could be dumped to a resistor, certainly heat sinking would be critical.
> 
> You are correct that "normal" 1206 resistors are designed for 1/8 - 1/4 watt. The ones I have are not. Kind of mind blowing, isn't it ? :naughty:



OK, I gotta ask since my mind is blown away. How much power are these "1206" resistors capable of dissipating? Normally, that kind of power is for wirewound types which are like little space heaters. But 1206 size, all that power in that little area means, well, you can do the math but the watts/unit area is pretty astronomical.


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## gadget_lover (Mar 6, 2006)

CM said:


> OK, I gotta ask since my mind is blown away. How much power are these "1206" resistors capable of dissipating? Normally, that kind of power is for wirewound types which are like little space heaters. But 1206 size, all that power in that little area means, well, you can do the math but the watts/unit area is pretty astronomical.



I already know, but don't want to spoil Harry's fun. 








Daniel


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## HarryN (Mar 6, 2006)

CM, your post is dead on - the power is really limited by the head removal rate, not by the actual rating of these resistors, so there is no point attempting to go any higher than these numbers. The few I have sold, I tell people not to go over 5 watts. That way, when they ignore me, they are still safe.

You might also ask "why the heck did HarryN have these made". Well, the long and short story is that my little "Breeze" light is resistored, and I designed it using 1206 resistors before I realized that the normal ones could only handle 1/8 watt vs my need to occasionally hit 1 watt. They were not easy or cheap to get.

I have a slight tendency to over design, and this "slightly higher rating', fit in with my personality. :laughing:


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## gadget_lover (Mar 7, 2006)

All that and harry didn't tell you what his resistors are rated for???? I seem to recall 25 watts are less than their rating, assuming a heat sink of some sort.

Daniel


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## CM (Mar 7, 2006)

In any case, at 5A, you probably do not want to add any resistance. A few hundred milliohms will drop the voltage quite a bit and you'll get that just through normal path resistance. One ohm will give you a nice dim yellow light. I don't know how much the C cells sag under load but my bet is that there is enough sag and enough resistance in the circuit that there's little danger in blowing out a bulb. Maybe the soft start is all we need.


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## petrev (Mar 10, 2006)

Thanks to AWR

and for all the other info too ( Did you do the Tail Mod and EMachineShop file ?)

I just downloaded EMachineshop and did a quick (rough dimensions) M6-tailcap insert.

Now with the material Al-6063 (?) and shipping to somewhere in DC (WHY ?) this seems to work out at about $5.30 each for 50 ( $7.60 each for 25 ).

Can I send this file to someone for checking and refinement and comments and material corrections and . . . 


OR ? ? ? where is the "real" file ? ? ? ?


cpf-x AT xuum DOT com

Cheers Pete


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## CM (Mar 10, 2006)

Wow Pete, wish I could help but I have no mechanical background. That's a nice rendition, and the cost is pretty attractive too :thumbsup:


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## petrev (Mar 11, 2006)

Hi CM (et al)

AndrewWynn is making some soon we hear . . . here

http://candlepowerforums.com/vb/showthread.php?t=103466&page=6&pp=30

His project for the M6 seems to be going forward nicely - new tailcap insert and regulated battery-pack at the last info.

Cheers to All


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## CM (Mar 11, 2006)

Thanks for the update. I hope this progresses forward.


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## nethiker (Apr 2, 2006)

I'm watching all you guys talk way over my head with great interest. Even without knowing what's really going on, the excitement in the exchange is obvious. Count me in should you decide to offer the fruits of your labor to the less technically inclined.

:goodjob:


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