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Jason_WI's

"Cox Pee Wee .020 with 3D printed horseshoe backplate"

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Reeds...........?

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Reeds...........?

Post  rsv1cox on Sun Nov 25, 2018 2:32 pm

There was a buried leading question in my SB Cleanup thread about me not being able to move around the new milar reed under the retaining clip like I can with original metal bronze? star reeds which have always worked better for me.

Bernie sells different kinds of reeds, milar, clear, metal, all rectangular, and roddie and others make their own.

Which kind of reed works best for you and are those rectangular reeds supposed to move around or just pulse?

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Re: Reeds...........?

Post  balogh on Sun Nov 25, 2018 4:31 pm

Bob I have been also wondering about the same issue for some time  and in my opinion the circlip should not hinder the free movement including the spin of the reed otherwise the sealing by the reed is compromised. I have the impression that old stock reedies have a smaller reed diameter than later reeds thus the latter will stick under the circlip in oldstock backplates like yours.

I bought from Matt several original berillium star shaped reeds for my postage stamp and older horseshoe backplates.I do not see them on his website but he and Bernie just acquired a huge lot of COX parts that they are just drawing up an inventory for...the star reeds may then become available soon..
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Re: Reeds...........?

Post  Dave P. on Sun Nov 25, 2018 5:06 pm

Yes. Inquiring minds want to know about substituting a rectangular reed for a bent star. Been wondering the same thing.
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Re: Reeds...........?

Post  Cribbs74 on Sun Nov 25, 2018 5:39 pm

In a nutshell the clip style reed retainer was meant for the thin copper reeds. Plastic reeds were used later on with the cup style reed retainer.

Since the copper reeds are not freely available, I just sand the face of the retaining clip until the plastic reed rotates freely. Doesn’t take much.

If the reed doesn’t move freely the engine will run like crap. Personally I use the stainless steel reeds as they last longer.

Ron

Roddie did some exhaustive research on reed thickness, maybe he will chime in and post a link to the thread.
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Re: Reeds...........?

Post  Ken Cook on Sun Nov 25, 2018 7:42 pm

I have used all kinds of different reeds and the clear Mylar is my preferred choice. I find them to offer more reliability in terms of not becoming glued to the tank during storage but they have a much shorter lifespan. They deform and become sucked into the venturi hole.  I noted that they were becoming stock items in Black Widows in the 87-89 years. I have some dated as 95 still using the circlip retention and these used clear Mylar reeds. This was also a transitional crossover point from metal tank backs to plastic. The beryllium stars were always in my older Babe Bee engines. I find them to be quite reliable but a lot more fragile. They seemed to be damaged in the packages as they were just sent loose in the plastic bag overhaul kits. All the loose hardware could damage them and those were the days you didn't receive another unless you bought another kit.

      The white Davis Diesel Teflon reeds claimed higher rpm's I had a issue with these on old circlip style reed retainer engines. This was on my best runner when the clip departed on a full out run. I truly feel and never mic'd the reed thickness that the Teflon reed was responsible for this.  The clip jammed into the side of the case making a bulge in the case. I couldn't believe it as it almost exited the case. From this point on, I recheck every circlip installed making 100% certainty that it's retained in it's groove and the reed rotates. I use the Mylar reeds and stainless reeds under the circlips with no issues. Keep in mind that there was also different circlip thickness's involved as well.


Last edited by Ken Cook on Sun Nov 25, 2018 8:17 pm; edited 1 time in total
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Re: Reeds...........?

Post  Mike1484 on Sun Nov 25, 2018 8:05 pm

Had the same problem last week building a few motors . Ended going back to the star reeds with the round clips . I like both the copper and mylar reeds . The stainless reeds are ok but I think that they may wear the reed seat out a bit quicker , stainless is a lot harder than mylar or copper . Good subject to bring up .

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Re: Reeds...........?

Post  Jason_WI on Sun Nov 25, 2018 9:17 pm

The circlips in the postage stamp backplates are a thinner wire gauge and fit well using the Mylar reeds in the metal tanks. Another reason to hoard the postage stamp backplates. As a bonus most had beryllium copper star reeds and if careful can be reused.
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Re: Reeds...........?

Post  NEW222 on Sun Nov 25, 2018 9:37 pm

Not wanting to hijack the thread, but I have a question regarding the copper star shaped reeds. And that question is if they have been bent or are slightly deformed, is there any way to reform them or straighten them out?
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Re: Reeds...........?

Post  fredvon4 on Sun Nov 25, 2018 10:33 pm

I successfully reclaimed 3 badly mangled copper beryllium star reeds

very flat 12"x 12"x 3" granite plate and one solid 2" x 2" x 3" chunk of brass bar stock

put the reed on the granite
propane torch to very red took about 3 seconds
brass bar on the copper and one smack with dead blow hammer

wrinkles krinkles and distortions gone

they were toast so nothing to loose....worked for me

scissors each ear as the reed grew in diameter slightly
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Re: Reeds...........?

Post  rsv1cox on Mon Nov 26, 2018 8:03 am

Thanks Ron, Now I remember your tip about sanding the inner side of the clip, you had mentioned it before. I tried it then and it worked well.

I finally investigated why there was a binding in my first Silver Bee. Took it apart and swapped cylinders with another Cox and it is the cylinder not the crankshaft as I had suspected. Either it was that way when I got it (thin wall #2) or I did it when I removed it from the case. There is no burr on the ports, rather it appears to be twisted. The main reason why I did not remove the cylinder from the later Silver Bee.



The reed systems on the later Sure Starts and for use in the cast cases have a much more looser arraignment. Lot's of space in there to move around.



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Re: Reeds...........?

Post  Cox International on Mon Nov 26, 2018 11:20 am

The interesting thing is that Ronald Valentine, who manufactures performance engines from scratch, insists that he prefers that the reeds don't turn and designs his setup so that the reed is pinched at the edges. Of course the reed still needs to "breathe" in the centre.

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Re: Reeds...........?

Post  getback on Mon Nov 26, 2018 11:48 am

Jason_WI wrote:The circlips in the postage stamp backplates are a thinner wire gauge and fit well using the Mylar reeds in the metal tanks. Another reason to hoard the postage stamp backplates. As a bonus most had beryllium copper star reeds and if careful can be reused.
Thanks Jason , I knew there is a difference in thickness but not were they came from . I make my own reeds from .005 " mylar from note book binders and trace from Bernie's reeds that come in a punch out sheet . Very Happy
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Re: Reeds...........?

Post  roddie on Tue Nov 27, 2018 2:33 pm

I'm surprised that there hasn't been more tinkering.. by the tinkerers with making their own Cox reeds. I would like to see some reeds designed and cut out using the "Cricut" (home/craft) machine. I would experiment if I had access to one. I think the star-shape (four-legs) design, holds some secrets to performance-tuning.

I bought some steel reeds (oval type) years ago, that are .002" thickness. I believe that both; Cox International and EXModel Engines have or "have had" the steel reed. The vintage Cox "copper-star" reeds are .001" thickness.. therefore the steel reeds are only slightly (.001") thicker.. and may not pinch/bind when using a circlip retainer. A downside to using the steel reed is that in time; it tends to "wear-off" the anodizing from the seat-area.

Most Mylar reeds that I've had.. have been .005" thickness. That's a LOT thicker than the old copper reed.  

I made a tool for "thinning" circlips.. allowing thicker reeds to be used without being pinched when the clip is snapped-in.

I've become a fan of the horseshoe backplate.. because the latest reed-holder designs use a flow-thru cap.. rather than an internal groove for a circlip. I made my own reeds from thin (.005") plastic that may have been Mylar. I made the basic shape of the old Copper-star by 1st cutting-out a circle.. then using a hole-punch to nibble x4 somewhat equidistant radiuses around the edge. They weren't perfectly symmetrical.. but they ran fine when installed in my engines.
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Re: Reeds...........?

Post  fredvon4 on Tue Nov 27, 2018 4:16 pm

steel, plastics, brass alloys, copper alloys, stainless alloys all sorts of shapes and configurations have been tried since the advent of the 2 stroke reed induction engine

Max HP usually means low life and frequent changes

Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze and spring copper, is a copper alloy with 0.5—3% beryllium,, Cox specked this alloy as durable and peak efficiency and COST>>>>>!!!!!

BTW any health concerns should NOTE 0.5 to 3 % Beryllium....and you have to eat or breath the beryllium to be any hazard and life time consumption by a Cox modeler would have to be massive....no, seriously the alloy is NOT that toxic until you feed rats with 30 reeds ground into their feed...

Rebuilding a 4, 6 or 8 cylinder 4 stroke IC engine with Babbitt bearings exposes you to 10,000 time more beryllium and lead than any Cox Reed....
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Re: Reeds...........?

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