Great pictures from the Gathering, Mark! That carb on Roger's plane has had me zooming in to look at it from all angles for half an hour. No idea, but it's a side draft with mixture control and a choke. Looks like he has the mixture control set up like the Zenith, with a twisting of the cockpit knob to screw the needle in and out and a tension spring on the needle screw. Oscar Zuniga Medford, OR
Oscar The carb is an old Tillotson off of an old Harley I believe. Someone gave it to me many years ago, so thought I would give a try. This is a Tillotson HD that uses a pressure control diaphragm. The HDs have a 37 mm venturi. The tube on the bottom is a balance tube to let the diaphragm see the same pressure as the intake sees. The pressure deferential created by the venturi will regulate the fuel available to the engine. I got the idea of the balance tube from pictures of Ellison carbs. They have the same diaphragm and balance tube built in. Without the tube, the diaphragm will close when the throttle is pulled back at higher airspeeds because of the ram air increasing the pressure on the fuel side of the diaphragm, causing the engine to quit until the throttle is opened back up. This always raises my stress to dangerous levels. (The port into the intake must be facing the incoming airstream.) The tube is only for balance between venturi pressure and ram air, not altitude compensation. Other that the use of a speedometer for the mixture control, this has been a very good carburetor. It runs smooth at all power settings and I can adjust the mixture in flight right where I want to run, and with the choke it starts and idles very well. The fuel distribution seems spot on. All cylinders burn the same. I have a 1.5 psi fuel pump to feed the carb, with a return line for excess fuel, but also have it plumbed to gravity feed as a backup. It seems to run fine on gravity feed. On the Harley you have only about six to eight inches of head pressure. I have seen these on Ebay, but have noticed the prices being asked are going up. I'm going to continue using the Tillotson, but I am trying to come up with a better mixture control, than a speedometer cable. Roger Bulla -----Original Message----- From: Oscar Zuniga via KRnet Sent: Sunday, October 11, 2015 11:21 AM To: krnet at list.krnet.org Cc: Oscar Zuniga Subject: KR> Roger's carb _______________________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org please see other KRnet info at http://www.krnet.org/info.html see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options
