LF thoughts on this finger design please

[Storm Rosson]

Or do the changer housing like Bud Carter did and just machine it with 1 or 2 axle support members instead of every finger like ShoBud and Ron do.You should really use a bearing , no more greasy as lube, no more lubing at all unless a pivot rivet gets some beach sand in it. As a side effect you will notice that the bearing actually reduces the tendency for the fin ger to not return all the way and reduces hyterisis as I believe it was Bud Carter making the ETS psg's and they used bearings every friction point where it was feasable. So like there's that and the school of Bent R. and Dave Wheelhouse and moir that don't like no plastic and think that it degrades the sound and are radioactive and causes cancer and genetic mutations oh and it's a gateway to sniffing glue sso I guess we don't like it....Stormy

[sleepingdog]

Ok. So Let's say I go with a bearing in the finger. What do I do about the lower plate where it goes around the axle? If I don't have some sort of bearing or oilite bushing or something like that on it then I'm back to putting oil on that axle, correct? So bearing on the finger would mean a bushing on the lower plate?

Also, I guess I would just make the finger narrower on either side of any support in order to maintain string spacing and provide room for the support, correct?

Dave

[Storm Rosson]

HMMMMM I didn't think the carter thing thru obviously, but if u use 3/8 drill rod I don't really think there is any problematic yield or distortion of the axle anyway,very few of the high quality pro steels use any axle support other than the housing at each end but that's my opinion. However apparently a majority of builders like Fred Justice, Gary Ritenberry, the Mullen crew, Beck and Dan Burnham, ad nauseum must not think it is much of ,if any of a prob either.My rant against plastic really only applies to load bearing contact surfaces like cross rods,primarily.Used as spacers or anti friction like Ron and me (I read his post and got some .002,4,6 PTFEsheet and punch anti-friction pads to go between scissor fingers , and on the sides of each finger-fulcrum where they hang from the axle. I use a "washer" of .002 stuck on each side of the fulcrum to address any side movement and subsequent rubbing on the support(s) on the changer housing. If you were to use some support like on the carters, surely with a little adjustment to fulcrum thickness one could eek out enuff space for at least one in the middle, making the axle(s) effective length less than 2 in. Again I really don't think yield(bend) in the axle of 3/8 hardened drill rod exists enuff ,esp on a 10 string, to affect anything. Online Metals.Com usually list the strength parameters like tensile, torsion, and yield if one wanted to reference the axle material(I ain't no engineer but I can drive this f'ing train) sorry drifted off again damn AADD . Looking at your pics again I don't see a real problem with the lower scissor plate being just like you have it designed. I can't see that it really bears much load at the axle or elsewhere so the bearing would be in the fulcrum only cause that is where the string load is. PS. I too like the idea and sound (BenRom) of brass fulcrum pieces, but it will wear and oval on a mild steel axle much less hardened drill rod. (I use drill rod also) course you prolly won't be alive when it happens .....but you never know

[sleepingdog]

OK, so you're saying bearing on the brass finger, don't worry about the lower scissor finger. I like that.

If I look at a design having a support between each finger, would the following seem reasonable:

Shaft Dia: 3/8
String Spacing: 11/32 = 0.344"
Brass Finger: 5/32 = 0.156" (same width as a R1038ZZ 3/8" ID 5/8" OD bearing)
Lower Plate: 16ga = 0.060
This leaves 0.127" remaining for supports. A little less once I factor in some clearances. Cool?

What gauge steel do you guys use for the scissor fingers?

@Ron, is that changer plate with the supports made from one solid piece of billet aluminum (or aluminium I'm guessing you call it ) Beautiful work!

Thanks for helping me sort through this, gents.

Dave

[maxi19]

Hi Dave, Stormy,

This is what the forum used to be like, people throwing in info and ideas. I use a TOOLSTEEL BIT 1/4" DIAMETER x 4" LONG (TMX HSS) as a shaft on my steels they are accurately ground, smooth and the length is ideal.
I cut out the PTFE washers with a compass cutter so there is no distortion by punching and they are a lot cheaper than punches.
My string spacing is 9mm
Brass finger 5mm
Finger plate steel is 1mm

I mill my changer block from aluminium bar

[sleepingdog]

[Clearly I wasn't thinking straight this morning, so I've fixed my post]

I think I would call what you're using for the axle a drill blank as in here:
http://www.kbctools.ca/products/CUTTING ... S/263.aspx
I like the ptfe anti friction spacer idea. Makes sense to me.

In each "opening" in the changer head between the supports, I would have the following, correct?

0.002 ptfe anti-friction washer/spacer
brass finger with bearing
0.002 ptfe anti-friction washer/spacer
lower scissor plate[/color]
ptfe anti-friction washer/spacer


Just ordered one of those compass cutters for $14 CAD delivered. Need to find a source for PTFE sheets now.

[Storm Rosson]

My ShoBud finger scissors thickness reads out to .063" thats 1/16" . Ron thanks for the com pass cutter tip bro, I havebeen frustrated because of the distortion tears and waste it causes never even thought about a compass cutter ...very cool. Dave those numbers appear quite accurate and almos exactly the same dimensions as the ShoBud changer I got from James M. Essentially 1/8" support between each finger, with a coupla of PTFE washer/pads on each side and it's friggen muy bueno. I gotta say Ron your changer housings look great and with each finger supported and useing (only)1/4 hardened steel drill rod ,I would venture to say that you haven't encountered any indication of axle yield or flexing, am I accurate? I thru in the (only)1/4" for dramatic effect when yer grey matter does an instant analysis of the whole axle shaft deflection thingy. Works pretty well no? As to the order of PTFE pads/spacers for your design I would go like this for each finger...pad/free side of fulcrum/fulcrum side between it and raise plate gets a pad/raise plate/pad on outside of raise plate between it and housing support member.Shit I hate gettin old ,tryin to get that sequential order took 35 min. Ron what do you think? about the placement of friction pads/spacers ? You can get the teflon in rolls like scotch tape kinda at Amazon. I got several thicknesses cause my precision perceptor wore out 10 yrs ago (at least).........this at least the 20th edit just for spelling and it still reads like a poorly schooled aardvark wrote it! I think the only diff between your order of spacer placement is the one between the fulcrum and the raise plate around the axle as there would be some friction between the fulcrum side and the raise plate when a lower pull is activatedhttps://www.amazon.com/s/ref=nb_sb_noss ... sheet+.002 linky to the zone where the PTFE lives.

[Storm Rosson]

Dave I just picked up the exact compass cutter Ron posted at the Zon for 6.91$ US....Stormy

[sleepingdog]

Thanks for the info and link. Having a hard time finding a supplier here in Canada. Would like to avoid cross-border shipping if possible - it's always a ripoff. Will keep looking.
Dave

[Storm Rosson]

After reading your post again, we do have tthe same spacer/finger/spacer/plate/spacer order doh!! Like Ron said ,this kinda idea slingin and tweaking discussions are great brain exercise and ,in my case,I always come away having learned something new and/or different perspective ..whatever I really do miss this kinda exchange WOOT!!...Stormy