SlotForum banner
1 - 17 of 17 Posts

·
Premium Member
Joined
·
1,841 Posts
Discussion Starter · #1 ·
Does anyone know where this material can be obtained please?

I am scratch-building a controller and need to make a custom wiper arm. In the past I have just cannibalised old controllers, but this time I need a broader strip than seems to be available from these sources.

Something in the back of my brain tells me that the material is a beryllium copper alloy, and that it is potentially nasty stuff health-wise if you cut yourself with it, but this may be an old slot-racer's tale.

Thanks,

Keith
 

·
Rich Dumas
Joined
·
3,600 Posts
The stuff to use would be phosphor bronze. I have some 0.008 inch thick stuff made by K&S, but that might be a little thin for your application.
 

·
Registered
Joined
·
3,588 Posts
Parma wiper arms are available as spares. Contact Parma stockists such as SCD or Slotrail

Alternatively you don't have to use a spring arm. A lot of scratch built and low volume production controllers don't use a spring arm, instead. they use a rigid arm with sliding type motor brush gear for the contact. The bush gear off an old C can or Parma 16d works well. The lever type brushes from motors like S can and FK isn't suitable for this sort of design although I suppose there might be a way to use it if you are only looking for low current motors,
 

·
Slot King
Joined
·
2,647 Posts

·
Tony Condon
Joined
·
3,044 Posts
what ian fisher used to do when we made ECe controllers was make the wiper froma solid piece of brass . Then fit to it, adjacent to the resistor or whatever is used on electronic handles a motor brush hood complete with a motor brush and spring , the brush contacted the resistor and the wire from it was attached to the wipe arm easy peasy

cheers tony
 

·
Premium Member
Joined
·
1,841 Posts
Discussion Starter · #6 ·
Joel, thanks for that. It looks to be the right stuff but what a massive minimum quantity! It would make about 850 wiper arms by my calculation. I need one.Anyone want to buy some of this sheet?

Tony, thanks. I remember the ECe controller well - I copied the basic idea and am using it now, but with a conventional springy arm. I tried the motor brush idea a long time ago with a wire wound resistor and the feel was horrible, but I can see how it would work with a smooth brass contact strip. The problem I have now with this is that I want my wiper to sweep three parallel lines of contact, so it needs to be trident shaped. Three sets of motor brushes looks like being over complex in this instance.

Rich, thanks for the offer, but I too think that .008 is a bit thin. Also, I'm not sure that the phosphor bronze would be tempered to a spring state. I'm sure its the berylium alloy I need.

Cheers,

Keith
 

·
Premium Member
Joined
·
1,841 Posts
Discussion Starter · #9 ·
Hi Leo,

Spring steel methinks. I have an old alarm clock spring made of this type of material, but its a b***** to work with and rusts like a good 'un, so I don't want to go there!

K
 

·
Registered
Joined
·
3,588 Posts
Beryllium copper is the ideal material for conductive springs, it's available from commercial suppliers but the big problem is they are only interested in selling way larger quantities than you need.

Phosphor bronze would probably be good enough, and it readily available from model engineering suppliers where minimum order quantities are much less of a problem although even that will probably do a lifetime's supply of wiper arms (even if they are a complex trident shape).

For example Macc Models offer 0.2, 0.4 and 0.7mm phosphor bronze sheet - I'm guessing 0.4 would be about right, they'll sell you a sheet big enough to make quite a lot of wiper arms for under eight quid (a fiver + p&p)

https://maccmodels.co.uk/materials-metal/phosphor-bronze-sections/phosphor-bronze-sheet.html

There are more supplier if you google phosphor bronze sheet suppliers uk
 

·
Registered
Joined
·
2,893 Posts
I don't know the shape you require. What about making the "arm" out of plastic or brass and cannibalizing three old scalextric controllers to get the springy bits. I think old controller were about 99p.

Whitenumbers.jpg
 

·
Registered
Joined
·
2,893 Posts
As I was playing with a take-out coffee spoon today. I thought these may suit. I bought half a dozen plus locally as they are made of small dia. brass/bronze rod which could be used for roll cages or nerf bars on sprint cars.

But they have a spoon like end and might be perfect for a controller?

3Pcs-Earpick-Spoon-Tool-Clean-Ear-Wax-Cu


Mine have smaller diameter rod but I can't find a picture of those as they come from our local market.

Maybe in a pound store?
 

·
Premium Member
Joined
·
1,841 Posts
Discussion Starter · #15 ·
I'm not sure about plain phosphor bronze sheet. Surely this would not be springy unless tempered correctly? - likely to be a tricky temperature controlled process.

Thanks for the link Impman. This looks a bit thin as you say but for under 3 quid I will get some. I could always double the thickness by soldering two layers together. I measured a wiper arm thickness as 0.22 mm. This sample is 0.15 mm so I have the choice of 0.15 or 0.30 mm, neatly bracketting the ideal. At 10 mm wide this is exactly what I want.

Thanks to all for the helpful suggestions.

Cheers,

Keith
 

·
Registered
Joined
·
2,893 Posts
I'm not sure about plain phosphor bronze sheet. Surely this would not be springy unless tempered correctly? - likely to be a tricky temperature controlled process.
Just wondering. If you take a piece of your chosen thin sheet 10mm wide and pull it over an edge to give it a bow. Then clamp between two flat surfaced and solder together. The bowed section will tend to pull the straight section and may give you enough "spring"?
 

·
Rich Dumas
Joined
·
3,600 Posts
The K&S phosphor bronze is springy enough as it comes, I did mention that I have used it for wiper arms in the past.
 
1 - 17 of 17 Posts
Top