Posted: 1/26/2010 21:35:54
Is anyone using, or heard of using an electric vacuum pump for istrumentation? My continental O-300 does not use a vacuum pump, and I don't like the look of a venturi. I am not looking for an IFR panel, but it never hurts to have the instruments there, and I have them from my old Cessna and don't want to purchase electric instruments.
Posted: 1/28/2010 11:27:49
Well, they're sold as standbys for IFR apps...But they're kind of pricey...http://www.aircraftspruce.com/catalog/inpages/aerosafeguardian.php
There is a systems that uses differences in Manifold pressure, but I have heard that they have some limitations due to theire operating characteristics of not giving a great deal of vacuum at certain engine conditions.
For VFR flying it might not make much difference.
Posted: 1/28/2010 19:02:11
You could use a standard vacuum pump and fabricate a solution using an electric motor of some kind. The other pieces required to make it all work add up pretty quickly though. The homebuilders kit is about $700.
You might want to consider glass panel. You could put this in as your primary panel and have the other instruments as secondaries.
Posted: 1/28/2010 21:39:49
I saw pictures of an interesting installation dated back in the 70's on an experimental aircraft. Basically it was an under the cowl venturi.
A flanged hole was installed on a rear cooling baffle. A piece of scat hose was attached, picking up high pressure cooling air from top of cylinders and led down and rear to the inlet of a venturi mounted on the engine mount at a 45 deg angle. Another piece of bigger scat on the venturi outlet led further down and exhausted in the low pressure area of the lower engine compartment.
The caption said that it would spin up a gyro while running up on the ground. Sounds believable but cannot confirm. Would be harder to ice up.
Posted: 1/29/2010 01:31:50
Nowadays I would look at Dynon Avionics or something like that.
Posted: 2/9/2010 19:49:16
I second the Dynon suggestion...get rid of the six pack of instruments and the vac pump as well, save the weight. That'll cost a bit over $2000.
On the other hand, google "slash tube vaccuum exhaust" for a REALLY simply vacuum source that runs off the exhaust, used in racing circles to reduce blowby gases in the crankcase. Not sure how much vacuum this would create but it might be worth a look. A slash tube is basically an angle cut piece of 1/2" steel pipe with a notch cut in it welded into the exhaust stream at an angle.
Posted: 2/22/2010 15:13:25
thank you for your input. I have been looking into Dynon.They are more affordable then I expected. I think I will probably go with the EFIS-100 and use the static instruments as backup (ASI, VSI, ALT).