Arc Systeme ProMagn Button

Big.Dave

New member
I've found a picture of the internal workings of this button on have a look.


Anyone know how reliable such a system would be. Also a shop has them in for about ?53.
 
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Henry147

New member
Speaking as an engineer. Looking at the design it should work very very well great idea. I will not consider anything else when I need a new button. The magnet idea is very good and simple.
 

Big.Dave

New member
Speaking as an engineer. Looking at the design it should work very very well great idea. I will not consider anything else when I need a new button. The magnet idea is very good and simple.
Thanks Henry for your opinion the idea made sense to me as well. It caught my attention when I read the bit about no springs and I thought to myself less to go wrong also talking to a friend who knows more about magnets then I do pointed out that magnetic fields are very consistant which is the name of the game in archery.
 

Whitehart

Well-known member
Does it work the same in both hemisphers or do you need two also will it be affected by your proximity to the poles when setting it up...:)
 

Big.Dave

New member
Does it work the same in both hemisphers or do you need two also will it be affected by your proximity to the poles when setting it up...:)
I don't need a compass to work out which way my arrows need to go mate!!:bowarrow::target:
 

Big.Dave

New member
I've decided to get one of these. It was a #### up between one of these or a Beiter button. My reason for doing so is its simple and as easy to tweek as my Bow sight, has fewer components, talking to some friends who know more about magnetic fields then I do, when I asked them about how consistant is a magnetic field the answer was very consistant to the point of over kill for what I need so thats good. I have not read anything bad about the quality of Arc Systeme products so should be ok.
The only con is its new and unproven.
The Beiter has been around for about 25 years and has a proven track record.

Well if it all goes pear shaped I still have my Shibuya DX in reserve ;)
 

Big.Dave

New member
Curious to know what the (moving) plunger weight comes in at.
Hi Joe I'll find out for you when I get it.
All I do know looking on the French archery forum is some one has posted possibly an Arc Systeme rep that the resistance can be adjusted from 100g - 500g also that its higher price is because it take 3x longer to make then their normal plunger (or Shepherd as the French call them) because they require tight tolerances. also the plastic tip is made from ERTALYTE TX which is low friction low ware materal.
 

Big.Dave

New member
it's arrived I managed to get a quick look at it before it got wrapped up. it looks well made and when I pressed the plunger it does feel different to my DX in that it felt more slick. after Christmas I'll have a review up with some pictures so you chaps can see for yourselfs:)
 

Big.Dave

New member
Ok here is the first part of my review
heres a couple of pics of what it looks like.





here's a rough translation of the instructions
principle of adjustment vaulted lay out D an adjustment of exit of your short prop has ugly L nut (N 8) after loosening of against screw (N 15). a simple adjustment of hardness s' carry out by means of L nut (N 5) after loosening of serrated roller (N 12) On this model the system dopposition of the magnets makes it possible to cover a sufficiently large beach without any disassembling we propose to you in more dune head titanium, a plastic head better adaptee for the arrows aluminum attention not to tighten the plastic head with the key! first magnetic shepherd in the world, head titanium, system patents. burger magnetic (race of 2mm) pressure (gr.) adjustment (24th of inch) burger arises (race of 2mm) pressure (gr.) adjustment (24th of inch)

It is a very simple button to use. 1 rotation of the big magnet is broken down into 10 clicks so from max pressure to min pressure is 70 clicks this is locked with a thumb screw. The locking ring has an O-ring to go against the riser and they provide a threaded bar so it can be locked tight against the riser also to note there are 2 holes in the locking ring 1 for the grub screw and one for the threaded bar. To attach the titainium head they provide a couple of small tommy bars so this can be secured tight as well and it's ok for carbon arrows, But the plastic head is for aluiminum arrows. Although I like to use plastic for my Navs.

Having had a good look at this button now I can say it is well made and finished. There has been alot of thought gone it to the design addressing the small niggles that other buttons have.
It is easy to set up if you have your old button already set just press it plunger to plunger to the the arc systeme button and adjust the tension on it so that both buttons compress at the same time with no springs to change this is very quick. it has a scale on it so you can record the settings, It should not be prone to rust that another well known button does. also easy to lock to the riser with tools provided.

I will report later on use and if it will fit my shibuya rest but I think it will be fine.

But even before I get to shoot with it on paper it looks alot better then the Shibuya DX but the price does have to be taken into consideration when making these kind of comparisons.
 

joetapley

New member
I'm not able to use my calibrated scales at the moment but the kitchen scales the plunger comes in at 5, with plastic tip fitted as opposed to 2.5g of a Shibuya
metal tip.
Cheers - is that 5 grammes for the plunger?

Joe, is it fair to assume that the weight of the moving plunger is significant?
Yes it is. The better buttons (like the Beiter) have very light plungers.

The force on the arrow from the button is the sum of the spring force and the plunger acceleration inertial force.

Quote from Old Sagi Board:

does anybody remember how to calculate the lateral push of a benting shaft?


To estimate this it's easier to work the other way round.
Say the spring force is 5 Newton (and assume it's constant)
Say the button depresses 2mm in 0.003 seconds
plunger acceleration is therefore 2*0.002/0.003^2 .= 444 m/s^2
If say the effective mass of plunger+spring .= 1.5 grams
Then force from plunger acceleration = 0.0015*444 = 0.67 Newtons
Total force between arrow and plunger = 5 + .67 = 5.67 Newtons

If riser is accelerating away from arrow at acceleration A then inertial force
becomes 0.0015*(444-A) m/s^2 (very back of envelope of course)
 

Big.Dave

New member
Cheers - is that 5 grammes for the plunger?

Yes it is. The better buttons (like the Beiter) have very light plungers. [/I]
Hi Joe yes it was 5 grammes.
All interesting stuff but how does the equation work when there are no springs but repelling magnetic fields?
And is the archer on the line going to notice a 2.5g-5g variation in plunger weight?



And just for anyone who is wondering I did happen to have a 36mm Beiter plunger on hand to weight and that came in at roughly 1.5g Joe is correct in the Beiter plunger being the lightest with the Shibuya next with 2.5g and after that the all metal arc systeme with a magnet on the end coming in at 5g.
 

geoffretired

Supporter
Supporter
Hi Joe,
I don't really follow the maths, but I can see that a heavier/or lighter plunger will move differently from a standard one.( if there was a standard one)
I am trying to think of how the differences would affect things.Does the flexing of the arrow cause the shaft to separate from the tip; or does the return push from the tip separate it from the shaft?Or do both work together like a springboard and a gymnast?
Could the differences between light and heavy be resolved by changing spring/magnet tension and/or centre shot setting?
If one system is more erratic than another, I could see we would not want the erratic system.
 

Big.Dave

New member
Hi Joe,
I don't really follow the maths, but I can see that a heavier/or lighter plunger will move differently from a standard one.( if there was a standard one)
I am trying to think of how the differences would affect things.Does the flexing of the arrow cause the shaft to separate from the tip; or does the return push from the tip separate it from the shaft?Or do both work together like a springboard and a gymnast?
Could the differences between light and heavy be resolved by changing spring/magnet tension and/or centre shot setting?
If one system is more erratic than another, I could see we would not want the erratic system.
Hi Geoff have a look at this for an idea on how a well tuned button should behave.[video=youtube;iIMpLv6U67w]http://www.youtube.com/watch?v=iIMpLv6U67w[/video]

Looking at how the button moves it suggests a slightly weak arrow because the button hardly moves and must have been set quiet hard.
 

geoffretired

Supporter
Supporter
Hi Big Dave, Thanks for that video.
I see the button hardly moves.To me, that suggests that she could shoot almost as well with a rigid button.With the button hardly moving, it would seem to me that the differences in plunger weights between two brands would have little change to the results in the target.
My thinking could easily be wrong, but the more I explain my ideas, the easier it is for those who know, to see where my ideas fail.
If the button was set softer, I would guess the archer was not so good and was using the softness to soak up greater variations in shot quality.OR they had set it soft for some other reason.
 
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