Mailing List flyrotary@lancaironline.net Message #63694
From: Todd Bartrim <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Elec Rad Fans
Date: Tue, 22 Aug 2017 14:45:07 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Hi Steve;
Here's a couple of pics showing how I sealed around the PSRU. The red material is a piece of welding blanket, so I'm not worried about temps. It also has hi-temp RTV sealant gluing it in place to the glass as well as the rivets.

This one shows how much foam/fiberglass I added to close the gap behind the spinner and to get close enough to the PSRU to use this lip seal

Todd

Todd Bartrim

On Tue, Aug 22, 2017 at 4:45 AM, steve Izett <flyrotary@lancaironline.net> wrote:
Thanks Todd for the explanation and the photos.
I did a seal between the front of the cowl by adding a glass disc with a cutout to match the front of Tracy’s box.
I used rubber bulb seal between this glass and box. Now I think about it I hope the box doesn’t get to hot for the rubber seal.
Perhaps I should add an insulating layer around the very front of the box (just behind the front bearing retaining plate)

Here is a link to a small video of an engine run on facebook- 

Cheers
Steve

On 22 Aug 2017, at 3:18 pm, Todd Bartrim <flyrotary@lancaironline.net> wrote:

Nothing fancy, but I just did a thorough job of exit ducting out of 3 of my 4 coolers. Intercooler, oil cooler, right coolant radiator. I didn't do an exit duct out of the left rad due to it's close proximity to the turbo. I just couldn't realistically make anything that would fit and be efficient and I figured it wouldn't hurt to have a little airflow over the turbo.
   Actually there is more to it as well. I spent a lot of time ensuring the cowl is well sealed to ensure that no air gets in there that hasn't done some work for me by passing through a cooler first. This included the diffuser inlet seal to the cooler face, but I believe the greatest gain was made around the prop spinner. I believe that Ed had warned of the pressure behind the spinner causing undesirable airflows into the cowl. I couldn't remember the details, but it didn't matter, I just knew I needed to block it. So while I was doing other fiberglass work I extended this face of the cowl by 3/8" to a closer tolerance with the back of the spinner. Then I made a lip seal on the top & bottom halves of the cowl opening around the PSRU to seal tightly here. This second part can be easily done on any completed aircraft, but the first one is much more work, however for those of you that have not yet reached that part of your project, I recommend that you pay attention to this detail. 
  When I built my engine mount, I only had the engine but no PSRU and no cowl, and no idea what prop I would use so with the data I could get from Tracy and Vans I did my best to build a mount that would put a prop spinner close to the face of the cowl. In any event, at that time I had no idea of the importance this would be later in improving airflows through the coolers.

   One other change I made that I've been meaning to bring up in another thread, that really only applies to those of us using 2 coolers (evap cores). Way back when, there was extensive discussion as to whether series or parallel plumbing would be best for cooling. The consensus at the time was that the less restrictive flow through 2 parallel rads would be best. Since I was also using an EWP (DaviesCraig) and many thought it would not have enough flow to adequately cool the rotary (just ask Paul Lamar, he'll tell you!), I figured I'd better go with the parallel rads. To do this I had to make some compromises in my flow routing and with everything else being equal, one of the rads will always have more flow than the other. But I was never quite sure that I had made the right choice as a series configuration would ensure all coolant goes through both rads for a maximum delta T.
  So with the opportunity during this rebuild I revisited this idea. My desire to include the Mocal Laminova heat exchanger pushed the scales over to the series configuration as trying to install it in any sort of parallel configuration that I could dream up would involve way too many ugly compromises. But a series install just fit beautifully and greatly improved upon the original plumbing.
  But will it work???? I gotta admit I'm holding my breath on this one, but so far it looks promising with all the ground runs. But so many other things have changed  as well that I still won't be able to say definitively which way is better.

Here's a pic of the right rad exit duct. Rather crude but it works.
Here's a pic of the cowl exit louvers that seal to this duct

Here's a few pics that show how I had to extend the face of the cowl to close the gap to the spinner

Here's the small but challenging intercooler. Unfortunately I don't have a pic right now that shows the backside of this exit duct where all the work was. But I made it from aluminum because of its very close proximity to the turbo. The crude fiberglass box seals tightly to the face of the intercooler and to the exit. So air takes a bit of a convoluted route.

Old Oil cooler inlet
New oil cooler inlet
Oil cooler exit duct. This seals tightly to the bottom of the cowl to use the stock RV outlet. I used aluminum here because of the engine mount it would be extremely difficult to do any sort of fiberglass molding. Aluminum I was able to bend and twist to get it into place then straighten it out.

Todd  -- sorry for the long winded reply, now my fingers are sore... :-)






Todd Bartrim

On Mon, Aug 21, 2017 at 10:41 PM, steve Izett <flyrotary@lancaironline.net> wrote:
Thanks Todd
Yep in Perth near Andrew.
Do you have photos of your duct work and what made the difference?
Steve
On 22 Aug 2017, at 1:10 pm, Todd Bartrim <flyrotary@lancaironline.net> wrote:

Long ago I had this same idea. To test it I put a cheap fan (one of those fans they sell for truckers to put on their dash) behind the right rad. It wasn't a great install, but it made no measurable difference on the ground and after a short flight the fan blades had completely broken off. I'm sure you would see better results with something like this
But I'm still not convinced it's worth it. The work that I've done with improved ducting seems to have made a world of difference and my temps are staying under control even with extensive ground testing. The temps get hottest after shutdown which I never experienced before (more in a separate post).
  However I would be curious to know the results of testing with a proper fan.
You are in Australia, correct? Davies Craig is a company from down under and I'm using their EWP's in my plane. They seem good to talk to, so give them a call and tell them what you plan on using it for.

Todd ---  It's a good thing I have no neighbors close enough to see me or they'd think I went nuts today, taxing circles in my driveway.

Todd Bartrim

On Mon, Aug 21, 2017 at 8:08 PM, Andrew Martin <flyrotary@lancaironline.net> wrote:
Steve, I don't think they are really an option, not much heat is generated at idle/taxi speeds, just weight and drag you don't need. other aspects will be at play like your exits etc.
There was tufting put inside a Bonanza cowl a few years back which showed complete reversal of flow through the cowl, explained why it would cool better on the ground with wind up its ass. prop probably sucking the air out.
I think this airflow stuff is sometimes dark magic.
Andrew

On Tue, Aug 22, 2017 at 10:08 AM, steve Izett <flyrotary@lancaironline.net> wrote:
Hi Guys
I seam to remember way back something being said about elect fans on exchangers in aircraft.
The reason for my question is if your prop doesn’t have very good blades for pushing air in tight to the spinner would an elec be helpful for sitting and taxiing?
My concern would be restriction of the incoming air once at speed and how it would go at high air speeds even with a good diffuser.
Has anyone ever used one?
I tried to emulate tracy’s 20b setup on the Renesis 4port 
I’ve got 540CI of Water cooler and 193CI of Oil cooler (out of RX7 turbo from memory)

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Steve Izett







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