Ohmen Cooling

[gangster]

In the process of completing an Ohmen. I notice there appears to be no provision for airflow over the motor or esc. The motor is a close fit in the cowl and the spinner pretty much obscures the hole in the front. There appears to be no exit vent. I recall an article by the WOO describing, by means of an analogy to our own digestive system, that the exit needed to be much larger than the inlet

 

Have other builders made provision for cooling or had issues?

For newer readers the WOO was a very respected and knowledgeable contributor to the mag  (search WOO or Brian Winch on this site

[EarlyBird]

For inlet I used a ventilated spinner and cut a hole in the cowl just below the spinner. The outlet is in front of the pilot made by cutting a large hole in the cabin floor.

[EarlyBird]

[EarlyBird]

The outlet can be seen on the right hand side of the blue bit, half of it, but it's the only picture I can find in my build.

 

[gangster]

36 minutes ago, EarlyBird said:

The outlet can be seen on the right hand side of the blue bit, half of it, but it's the only picture I can find in my build.

 

Thanks for that. It looks like you have gone for a single cockpit version and rearranged bulkheads accordingly and put nice big cutouts in them to improve airflow.I like the extra hole in the cowl, I had that in mind. possibly slots in the lower sheet behind the firewall. Not sure if I have sufficient holes in the formers to exit through the cockpit 

[gangster]

47 minutes ago, EarlyBird said:

What motor have you used? On mine there seems to be less clearance around the prop shaft The front of my motor extends into the front of the cowl with a tapered hole to allow it clearance to rotate. I have used a turning 3536/8 spaced from the bulkhead 6mm 

[EarlyBird]

23 minutes ago, gangster said:

What motor have you used?

Same motor turnigy 3536 900 kv. I built the cowl to fit the motor. Like this

 

 

 

[gangster]

3 hours ago, EarlyBird said:

 

1 hour ago, EarlyBird said:

Same motor turnigy 3536 900 kv. I built the cowl to fit the motor. Like this

 

 

 

What motor have you used? On mine there seems to be less clearance around the prop shaft The front of my motor extends into the front of the cowl with a tapered hole to allow it clearance to rotate. I have used a turning 3536/8 spaced from the bulkhead 6mm 

[gangster]

Ah shortened cowl. That explains it. Will just make a larger hole below in front and also have a think where the heat exit will go Probably in bottom sheet. Tempted by the servos at the back and hopefully the balance issue will be offset by the moter being a tad further forwardThanks for your ideas

[Trevor Crook]

Been a while since I built mine, but as I recall the plan does cater for cooling. Air entry is via the hole in the front of the cowl, below the spinner. I think there is a hole in the firewall below the motor through to the ESC compartment, then holes in the battery bay floor to let the air flow upwards. Finally it can exhaust via the hole in the cockpit floor shown in Earlybird's photo.

[Trevor Crook]

Just looked at Peter's original Ohmen thread, photos at the beginning show the construction, there's room for air to go up past the battery tray. The hole in the cockpit floor hasn't been cut in the bare wood photo, but can be seen in later pictures of the finished model.

[gangster]

Thanks Trevor. I better have another look at the plan and mag article. Don’t know how I missed them unless they were not on the free plan. 

[Peter Miller]

Trevor has got it right.  Mine is over 5 years old, been flown an awful lot, never suffered any problems with cooling

[gangster]

Yep just me being thick/ blind. I can see the inlet on the plan now on closer inspection and it is visible in the photos I have now also seen the note on the top of the plan. Thanks for your help and for humouring me guys 👍