Posted 14 Nov 2016 Replaced the trim cable that broke and can already see that it will break again with use. So will attempt to install electric trim. Hoping somebody here already has a Bandit with electric trim and will make my job ridiculously easy by posting or sending pictures of what they did. Any pics or advice sincerely appreciated. Don54VH Avid Bandit/Subaru/tri-gear Share this post Link to post Share on other sites
Posted 14 Nov 2016 'Just curious... What is the issue that is causing the trim cable to break? Share this post Link to post Share on other sites
Posted 14 Nov 2016 It's set to pull on the 'down' trim and push on the 'up' trim. The trim seems to be too heavy (?) for the cable to handle, so pushing the 'up' trim will slightly bend the wire between the wire housing and the trim tab. Bound to weaken the wire over time. Share this post Link to post Share on other sites
Posted 14 Nov 2016 You got me confused - which don't take much - usually, the wire pulls the trim tab down which makes the elevator and the nose go up, and pushes the tab back into the neutral position - at least that is how mine was made, and the electric trim worked the same way. The trim tab should work easily without resistance. There are two different wire sizes for Bowden cable - I think the larger one is about .070" diameter, about 2x the size of the smaller wire. A photo of your setup would probably help. EDMO Share this post Link to post Share on other sites
Posted 14 Nov 2016 The electric trim works very nicely, the MK IV builders manual on this site covers what you need to know. Their other alternative is the spring trim that Sonex and many other planes use. The Q2 that I have uses it, was designed with it and it works great. I believe that TJ has it install on his KF1 build. Share this post Link to post Share on other sites
Posted 14 Nov 2016 Here's the write up I did when I replaced my elevator and added trim.It's pretty straightforward to wire it up. Share this post Link to post Share on other sites
Posted 14 Nov 2016 That's correct, Ed. Pull on 'down' and push on 'up'. I have the smaller wire, which is probably the problem. The swing on the trim tab causes a small bend in the wire travel. I'll take a pic of it and post. I'll dig out the manual, Paul, and see what I can do with that. Thanks, both of you.Don Share this post Link to post Share on other sites
Posted 14 Nov 2016 Cables are designed to pull ONLY. A system like this should have a spring to push the horn away with the cable to pull it back. An easy way to do this is to place a compression spring over the exposed cable from the fixed housing mount to the trim horn. This will give the cable the push it needs to stay under tension. A better way is to use two cables each pulling on opposite sides of the tab. Share this post Link to post Share on other sites
Posted 15 Nov 2016 Evidently age does not equal knowledge! Posting a pic of the 'way things are' and after next week, should have a new picture of the corrected connection. I really do appreciate the advice and comments of you guys who have been there and done that. This learning curve is not fun! Or maybe 50% fun and 50% frustration. Don Share this post Link to post Share on other sites
Posted 15 Nov 2016 I have a similar cable on my MK IV, and have never had a problem with it. Flew the plane about 450 hrs. I really didn't use the trim much though. I would set it for hands off cruise and pretty much leave it there. Never used it on landing. Stick forces are pretty light I think. I didn't have the spring on mine though. That would put more pressure on your cable in the push mode. Couple of other thoughts, try the heavier cable, it shouldn't bend so easy. Aircraft Spruce sells both. The other thing is that the bolt the cable attaches to has to pivot freely or the cable will want to bend. I do know one other thing about these trim tabs. If the cable or push pull arm (as in the case of the electric trim) comes undone, you will get a lot of flopping around of the elevator. Fortunatly when it happened to me, (with electric trim) I was just taking off, and was able to limp around the pattern at slow speed and get it back on the ground. If it had happened at high speed, it could very well have got ugly. JImChuk Share this post Link to post Share on other sites
Posted 15 Nov 2016 Evidently age does not equal knowledge! Posting a pic of the 'way things are' and after next week, should have a new picture of the corrected connection. I really do appreciate the advice and comments of you guys who have been there and done that. This learning curve is not fun! Or maybe 50% fun and 50% frustration. DonThat spring is trying to compress the cable.It is doing opposite what is needed. Share this post Link to post Share on other sites
Posted 15 Nov 2016 I can see some function in the spring. Suppose the cable breaks while in flight, the spring should then hopefully be strong enough to pull the tab against the stop and keep it from flopping in the breeze like mine did. If the stop is in the right place, your trim may then be set up for landing. I still say go with the heavier cable and make sure the bolt can pivot. JImChuk 1 person likes this Share this post Link to post Share on other sites
Posted 23 Nov 2016 I had this problem on another aircraft...the inner cable was sticking out about 6" and I put a 4" piece of small aluminum tubing over it that helped take the flex out of the cable but still allowed the cable to travel the full distance both ways.the color of your cable looks like it might be a more mailable metal than standard cables. You might buy an aircraft grade cable and just slide the center cable out of the new one and into the old housing.Another idea would be to extend the trim tab arm so that you can use leverage to override force. You could swap the spring hole with the cable attach and gain a little leverage without any modification... Ron Share this post Link to post Share on other sites
Posted 23 Nov 2016 (edited) I agree, the spring should push the tab back up, and not pull it down, but either way could prevent flutter. It can be a challenge to get the spring pressure right so your trim stays where you set it. I cant figure out what the other angle gizmo is above the cable - the one with a bolt and slot in it - what function does it have? I am guessing it is a stop - if it binds, or has friction, it could put a strain on the cable - mine never had one - my tab hits the elevator tube in neutral-(up) position, and the controls and cable limit the travel down. Some have put a pull spring on the top of the tab, others have made an internal setup which I don't care for, and some have used two cables and that is double cost and work. EDMO Edited 23 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 23 Nov 2016 I am pretty certain the spring should pull it down. I dont know about you folks, but I hardly use nose down trim unless I am really loaded up in the baggage compartment. Most flying in mine is at full nose up trim (pulling down on the tab). Think about it. If the cable breaks and it goes to nose up trim, you can get the nose back down easily with the flaperons. If the spring is pushing and goes nose down trim, you have to fight the stick till you get it on the ground. As I said before, the cable pulling to get the nose up is the only way that makes sense in a single cable system. Spring pulling down to keep the nose up... only one that make sense in a single cable system. 1 person likes this Share this post Link to post Share on other sites
Posted 23 Nov 2016 (edited) I don't think I ever needed nose down trim either. That's why a piece of bungee cord tied to the seat truss and going around the joystick works real good on an Avid if you don't have a trim tab. Just slide the bungee up the joystick to put more back pressure on the stick. Cheap, simple, effective, and almost impossible to break. You seldom get that combination on any part in an aircraft. ;-) JImChuk Edited 23 Nov 2016 by 1avidflyer 3 people like this Share this post Link to post Share on other sites
Posted 23 Nov 2016 35 cent fix. Trim up with this. Trim down with the flaperons. My push pull cable never worked either. To much play in the cable through the fuselage. 4 people like this Share this post Link to post Share on other sites
Posted 24 Nov 2016 35 cent fix. Trim up with this. Trim down with the flaperons. My push pull cable never worked either. To much play in the cable through the fuselage.How much do you have to move the trim handle to make a change in the system? Looks like a fairly simple system once you have it all in place. I have the Bungee system that Jim talked about up a couple posts. It works well but the bungee is sprung now and needs to be replaced. This spring idea wouldn't ever do that. 1 person likes this Share this post Link to post Share on other sites
Posted 24 Nov 2016 Not much movment at all. It does depend on how strong of a spring you have. Stiffer spring less movment. 1 person likes this Share this post Link to post Share on other sites
Posted 24 Nov 2016 (edited) Bandit, I like your spring trim. What did you do with the trim tab if you eliminated the push-pull cable? I think if you could get a remote control system for the trim tab that would be great - No wires and It works with RC planes. EDMO Edited 24 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 24 Nov 2016 I connected it to a turnbuckle so I could rough trim it on the ground. When in flight I can fine tune it with the trim control. 2 people like this Share this post Link to post Share on other sites
Posted 3 Dec 2016 Snapped this pic from at Aerotek 220. Clean set up. 1 person likes this Share this post Link to post Share on other sites
Posted 4 Dec 2016 That's the proper way to rig those type of cables! Share this post Link to post Share on other sites
Posted 4 Dec 2016 Snapped this pic from at Aerotek 220. Clean set up.Joey, any idea how his trim was set up inside? Share this post Link to post Share on other sites
Posted 4 Dec 2016 (edited) I used to inwardly smile when I was doing my unusual attitudes instrument training in the Cessna 150 with the hood on, my eyes closed and hands in my lap - The trim wheel squeaked, and I could tell by the sound that the CFI was cranking in all the trim one way or the other and I was going to have some heavy pressure on the control wheel to get it flying while I cranked the trim the opposite way. Once, he used it to cover the sound of the flaps going down and I really had my hands full getting straight again. EDMO Edited 4 Dec 2016 by EDMO Share this post Link to post Share on other sites
