From: "Finn Lassen finn.lassen@verizon.net" <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 18:47:48 -0400
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Thanks Charlie,

I was planning on using 1/4" plywood wrapped in fiberglass. (Tracy had 
warned me.) I do have a length of 6" OD 0.035 SS pipe, but what about 
the ends (or end opposite throttle body)?
I can weld SS with my Henrob, but no success with aluminum. Also the 
curve of the pipe would make me shorten the intake runners a bit to make 
room around the bell mouths.

I started reading the grapeape-inductionsystems.pdf paper and realized 
that's going to take quite a bit of study and research. Like what is the 
VE (Volumetric Efficiency) of a Renesis?

Seems I start with the best intentions to design the optimal 
installation and end up copping out and doing "looks about right" or 
"what he did".

Like, I have no clue how big my air intake opening should be. Just the 
size of the throttle body? Tracy mentioned something about the air 
intake should gradually open up to the size of the throttle body. I 
should now have plenty of room in the left cheek for a straight run from 
near the prop to the throttle body mounted on the plenum (shoe box).

Finn

On 9/12/2019 5:26 PM, Charlie England ceengland7@gmail.com wrote:
> 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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