Carb heat and the Robbins muff

[dsmithlib]

I am building the filtered airbox with carb heat using Robbins muff and his enclosed flange. As I got closer to installing the door underneath the flange it occurred to me that the door opening was going to be larger than the enclosed flange. Why would I do the full size door cutout underneath my nice enclosed flange?

The door of course needs to large enough to block the ram air inlet. If I cut the opening per Van's plans, the opening is just 1/8 less than the door.

I have not seen any references to people undersizing the opening to fit under the enclosed flange.

I thought I would see if anyone had good insights or pix of this particular intallation. There is quite a bit of effort that comes together when you attach the door, hinge, arm and flange.

Thanks,
Dave

[cjensen]

I have the Sam James air box (cone), so I can't help from personal experience, but got any pics of yours so we can see it?

[captain_john]

Dave, I gotta be honest. I had to google up Robbins heat muff to know what you are talking about. I never heard of it! For those like me, here is the link:

http://robbinswings.com/index.htm

Looks like an awesome (huge improvement on Vans) design!

Pics would be helpful. I agree with Chadley.

CJ

[Spike]

I think I know what you are getting at...

Is it possible to move the flange towards the ram inlet so that the taper of the inlet portion requires a smaller sized door? The second question would be if we are sure that we need an really tight seal between the door and ram air inlet. My thought would be that it doesn't matter so much if there is some leakage as long as the majority of the air comes from the heat muff.

Spike

[Spike]

I also added them to the resources section for future reference in purchasing heat muffs.

Spike

[dsmithlib]

Thank you for your interest in my airbox dilemna. A discussion with Van's lead to comment like......we have heard of O360's where the airbox needs to be shifted to (starboard). Well, I have one of them. This rebuilt engine began as an O360-A4K and I have not yet figured out WHY it is different but, it is.

It turned out that my airbox needed all of the modifications. 1) turning up the top plate; 2) trimmed the inlet; 3) cut new top plate to shift carb position and 4) the filter needed minor nip and tuck (less dramatic than the O320 instructions describe).

There is a possibility that I could have placed everything shifted to starboard 3/4" and avoided the modifications to the filter. It still would have required a new top plate and the filter placement and shape would have been slightly altered. To do this, the instructions would have needed to include a check in the beginning to ensure your carb is where the design expects it to be.

It looks like it will be fine - it just took a lot longer. I have documented the steps on my blog at www.rv7preflight.blogspot.com

Thanks.....[/img]

[Spike]

Glad to hear that it worked out


Thanx for the update!