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PMag Cooling Shroud

I said:
I would guess the 3D-printed shroud or corrugated-surround would provide more even cooling to the unit, so why not?
I should add that my heat dots did go dark a while back. I replaced them with 190-210 strips and it has gotten up to 200. This is with the traditional blast tube configuration.
I think it's probably the after-shutdown heat soak however so I don't suppose the blast tube or shroud would help. But I do now open the oil door after shutdown as a matter of course.
 
I'll take you up on that.

Here is a basic cad model of the PMAG I drew up. If you can take measurements of the listed dimensions (preferably with calipers) I can get a shroud designed. If you can't get all the measurements, I can use what you can get and take a guess at the rest, it just may take a 3D printed prototype or two to get it perfect.
 

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I cannot provide the dimensions in a timely manner but I am interested to buy two sets of Emag cooling shrouds should they become available.

Bevan
 
Here is a basic cad model of the PMAG I drew up. If you can take measurements of the listed dimensions (preferably with calipers) I can get a shroud designed. If you can't get all the measurements, I can use what you can get and take a guess at the rest, it just may take a 3D printed prototype or two to get it perfect.

Kyle - what do you think of a two-piece shroud (halves) held together with #6 screws and nuts?
 
Think about what a shroud does, particularly after shut down.

Testing shows that post-shut down is where the accessories experience the most heat as the heat soaked engine transfers heat to the accessories (which were receiving cooling airflow until the engine stopped).

Do you really want to put a shroud around one of those accessories and trap all that heat inside the shroud?
 
Kyle - what do you think of a two-piece shroud (halves) held together with #6 screws and nuts?

That's actually what I was going to do. Either two halves with two bolts and molded in nuts, or two halves that are hinged and have one bolt to secure it.
 
We have a local RV-4 with IO-360 built in the late 1980's and the builder put two small doors in the top of the cowl centered, back to back with piano hinges. They had small flat magnets like cabinet magnets to keep them in the closed position. When the owner lands and shuts down he reaches up on the top of the cowl and pushes both doors down so they release from the magnets and swing freely. You can watch the heat come out of the slots with the hot air skewing the daylight like a mirage. When he starts the engine the cowl pressure immediately forces the two small doors to close up to the magnets. During flight the positive pressure of the upper cowl keeps them sealed up nicely. Fairly clever but I think he got the idea from another aircraft he saw at a fly-in. This helped with the chronic vapor lock hot start issues with the injected engine.
 
I dont have any PMAG issue, but post-shut down heat under the cowl is significant and I do find that hot restarts can be problematic. To assist cooling under the cowl after shutdown I put a little 75 cfm 80mm 12v muffin fan in the oil door opening and wired to my battery charging port. Installs in seconds. I have it run for an hour on a little electronic timer after shutdown. I haven’t given it the full test yet, other than current draw, but preliminary temp and hot starting tests look very promising toward ameliorating post-shutdown under-cowl temps.

..
 

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Here is current design for the cooling shroud. It is designed to be hinged on one side with a countersunk 6-32 acting as the pivot pin, and have the other side secure with a 6-32 screw. Both of these will go into threaded inserts in the plastic. For the cooling hose attachment, does anybody have dimensions for the hose? Right now I just have the attachment point modeled as a 5/8" ID hole, but I can add features to secure the hose if I have dimensions.
 

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Here is current design for the cooling shroud. It is designed to be hinged on one side with a countersunk 6-32 acting as the pivot pin, and have the other side secure with a 6-32 screw. Both of these will go into threaded inserts in the plastic. For the cooling hose attachment, does anybody have dimensions for the hose? Right now I just have the attachment point modeled as a 5/8" ID hole, but I can add features to secure the hose if I have dimensions.
I am not sure if this will work without any [field] modification. There are two clip that holds the PMAG in place and those stick out about .325 and it is not clear if the stud bolt will also interfere or not.

My cooling hose is a 3/4" ID hose.
 
I am not sure if this will work without any [field] modification. There are two clip that holds the PMAG in place and those stick out about .325 and it is not clear if the stud bolt will also interfere or not.

Tough to get a good photo of the area.
 

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The mounting lugs are about 15 degrees off vertical with the top lugs indexed toward engine center.
 

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PMAG reports internal temp and it would be interesting to see if this type of shroud will decrees the temp and if so, by how many degrees.
 
I show the same temp range with the simple recommended solution. Why risk changing what has proven to work well!
Same for me on the temps with a Van's spec blast tube but I do like the idea of the shroud.

Not to be a downer, but over time would the plastic shroud wear on/through the PMag surface finish?

d
 
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I had an RTD on the PMAG of my RV7 for 9years.
Long since sold but I assuming still there…
Anyway. As mentioned above the absolute max temp was always heat soak after shutdown. Practical mitigation of that sounds hard.
They are obviously fine to soak up to well north of 200F and therefore by definition run for short periods on restart at that temp.
20min turnarounds are probably the worst. They do cool quickly.
This was a hot day short turn.

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BF251554-268D-48B9-AB6E-0EB6BD3FE6E0.jpeg.
 
Attach this fan to oil filler door and direct airflow to engine compartment. Dissipates hot air. Use it to prevent hot start problems in the Florida heat.
 
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