From: "Charlie England ceengland7@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: Intake progress
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Date: Thu, 12 Sep 2019 16:26:47 -0500
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Like most people's dad used to say, "Don't do as I do (did); do as I 
say." :-)

Tracy looked at my box after it was built & pointed out what I should 
have considered: those big flat (thin) aluminum panels won't survive 
intake pressure waves. I knew better, but that part of my mind had gone 
on break during the entire construction of the box. Car makers don't 
waste aluminum making cast 1/4" thick plenums just to get rid of surplus 
aluminum. :-)

That box is now lined with 1/4" plywood and fiberglass, and weighs far 
too much. I'm doubtful that it will be a flight item.

I'd suggest doing what Tracy did, & start with plywood/fiberglass, or 
use a 4"-6" round aluminum tube for the plenum. I can probably dig up 
some 6" if you want to try it, or check local farm-market publications 
down there for surplus irrigation pipe.

I never did find any tube length/plenum sizing advice for the rotary 
that I trusted. Very few Renesis car guys ever touch the stock manifold, 
since it would be very difficult to improve on Mazda's design for a car.

Charlie

On 9/12/2019 12:02 PM, Finn Lassen finn.lassen@verizon.net wrote:
> 6 1/2 years later I'm about to do the same and would like to ask the 
> same question before I make my "shoe box":
>
> "I'm curious about how others have adapted the common Helmholtz intake 
> tuning formulas to the rotary. Would anyone care to 'show their (math) 
> work'?"
>
> Rather than building it as big as possible, I'd like to know if there 
> is an optimal size.
>
> Finn
>
> Charlie's photo:
>
>
>
> On 2/17/2013 3:41 PM, Charlie England wrote:
>>
>> Now that everyone's awake again, I thought I'd send a pic of my 
>> intake progress (RV-7 Renesis with James Lyc cowl). I played with a 
>> couple of different materials for the bell mouths. I tried gluing up 
>> some 1/4" plexi from an old windshield, but used super glue instead 
>> of proper plexi cement (which I wasn't able to find locally in a 
>> hurry). The 1st try popped apart on the lathe; the 2nd turned out ok. 
>> Next effort was with 3/4" MDF (medium density fiberboard). That went 
>> well, until I put a little too much side pressure on the ring 
>> (homemade cutting tool) after undercutting the center section. 
>> Overall tube lengths will be ~11 3/4" block surface to bell ends. The 
>> plenum is *much* bigger than most tuning sites recommend. I figure 
>> that I can experiment with plenum size by just stuffing it with rigid 
>> foam to take up some volume, if needed. Going the other way wouldn't 
>> be so easy. :-)
>>
>> Since I don't have Mark's TIG skills, I thought I'd ask what others 
>> have used in joining thin wall tubing to 1/4" aluminum plate. 
>> Aluminum brazing rod? High temp epoxy? JB weld? I do intend to add 
>> bracing from the plate to the plenum assembly to take some of the 
>> cantilever & vibration stress off the tubes.
>>
>> I'm using this length and concept because Tracy has had great luck 
>> with both HP & BSFC on his Renesis with a similar configuration. 
>> However, I'm curious about how others have adapted the common 
>> Helmholtz intake tuning formulas to the rotary. Would anyone care to 
>> 'show their (math) work'? Renesis users would be better for me, but 
>> any calcs would do. When I tried to adapt the common formulas to a 
>> rotary, I was getting 'interesting' results, so I'd like to know if I 
>> got lost somewhere while trying to plug rotary 'valve' timing into 
>> the formulas.
>>
>> Charlie
>> (Sorry for the sideways iphone pic; I guess you can pretend that 
>> you're looking down on it...) 
>
>


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