Author Topic: Small ( 1/2A) 3- line bell crank (Read 3338 times)

Bill Heher · « **on:** September 15, 2016, 03:03:38 AM »

Did J- Robert's ever make a small 3-line bellcrank? I am building a Jim Walker Fire- bee, but do not want to try the Air bulb throttle. The AJ website showed a 3 line system on the proto- type..... help!

Wayne J. Buran · « **Reply #1 on:** September 15, 2016, 05:46:39 AM »

Bill, I think you are referring to the earlier version J. Roberts. They are usually available on E-bay or at your local swap meet. Handle, and two types of B/C, upright and inverted. Somewhat like the current item sold by Brodak. Handle us is normaly not interchangeable with current Brodak offering. Handle of early model is marked with "J. Roberts' only. B/C's were packaged in blue print boxes (upright) and (red) inverted models and they are smaller and thinner than current. Hope this might help.
Wayne

Tim Wescott · « **Reply #2 on:** September 15, 2016, 10:10:04 AM »

Air bulb throttle?

john e. holliday · « **Reply #3 on:** September 15, 2016, 06:36:17 PM »

Yes, Jim Walker used a squeeze bulb on a plastic tube to flap like thing that closed over the venture when squeezed.

skyshark58 · « **Reply #4 on:** September 15, 2016, 07:32:51 PM »

It was used on his .049 engine and didn't work very well. Whole bunch of drag from that tube and the whole system was prone to leaks and the tubing coming off somewhere. I had one of his T-28s that came with the engine and all the stuff to make the system work. Best thing was the aluminum prop! Mike

john vlna · « **Reply #5 on:** September 16, 2016, 08:34:52 AM »

I would used a balanced BC system. This can be set up with a normal 3 line handle. I have done this many times with sig 1/2A bellcranks. The attached shows a larger model but the idea is the same for a smaller plane.

PS sorry the pictures are a bit blurry, my camera's focus has bit the dust.

JoeJust · « **Reply #6 on:** September 16, 2016, 08:52:00 AM »

Here's another look at what John has shown. it is a system I have used and sold for years, and it works with just about any 3-line handle. Use metal bell cranks and save a bit of space.
Joe

Bill Heher · « **Reply #7 on:** September 17, 2016, 12:32:20 AM »

I have a stash of Perfect small aluminum bellcranks, plus a couple RObert's originals and a RObert's handle.
On the balanced unit made from regular bellcranks, does the geometry/ throws work with the RObert's handle?

JoeJust · « **Reply #8 on:** September 17, 2016, 07:28:22 AM »

Quote from: Bill Heher on September 17, 2016, 12:32:20 AM

I have a stash of Perfect small aluminum bellcranks, plus a couple RObert's originals and a RObert's handle.
On the balanced unit made from regular bellcranks, does the geometry/ throws work with the RObert's handle?

Works well for me! On he 200 Wildcats I shipped I did not receive one complaint. However, as you make your way upwards there is the chance that you might consider a matched set of Brodak handle and bellcrank. Or, give 2.4 a try. It is a lot of fun, and basically a lot cheaper. All the top guys on a National level use a matched set up, but for others that don't want to push the envelope, the "home made" cranks work just fine.
Joe
PS My advice and $3 will buy you a cup of coffee just about any place. (other than Starbucks)

john e. holliday · « **Reply #9 on:** September 17, 2016, 11:25:52 AM »

Those types of bell crank set up for throttle control is great if you use the Fox bell cranks. I will never use the set up on any thing bigger than a 15 size plane after a pull test at a NATS years ago folded my set up. Already had one official in when the person on the scales pulled harder than I ever pulled to that point. Since then the scales are now anchored and would be my fault for over pulling.

Author Topic: Small ( 1/2A) 3- line bell crank (Read 3338 times)

Bill Heher

Small ( 1/2A) 3- line bell crank

Wayne J. Buran

Re: Small ( 1/2A) 3- line bell crank

Tim Wescott

Re: Small ( 1/2A) 3- line bell crank

john e. holliday

Re: Small ( 1/2A) 3- line bell crank

skyshark58

Re: Small ( 1/2A) 3- line bell crank

john vlna

Re: Small ( 1/2A) 3- line bell crank

JoeJust

Re: Small ( 1/2A) 3- line bell crank

Bill Heher

Re: Small ( 1/2A) 3- line bell crank

JoeJust

Re: Small ( 1/2A) 3- line bell crank

john e. holliday

Re: Small ( 1/2A) 3- line bell crank