Viking Steel Bungee
Viking Steel Bungee
The Viking Steel Bungee was developed from customer requests and our own need for something better. The goal was to create something to fix a problem while still trying to keep things as close to the intended design. With over 1200 sold, it has proven to be a simple, yet effective design. Some customer stories below.
To adjust tension:
1) lift nose of the plane off the ground
2) disconnect and remove steering rods in order for them not to interfere
3) Sit in the plane and test rudder pedals. They are now disconnected from the nose wheel and you have two individual systems you can tweak. The pedals and rudder is one, the nose-wheel strut is the second.
4) in order to try the rudder you need both feet on the pedals and feel where there is friction. Lubricate / repair / remove fairleeds as needed for more direct routing.
5) for the strut, tighten the center rod until the entire assembly is loose vertically (up/down) between the top firewall shelf and the black nylon steering V block at the bottom. You should be able to lift the assembly away from the bottom block, after tightening the center rod. Your center rod should have a long coupling nut on it. Don’t bottom this out, add a spacer if needed. Once the assembly is loose, back off the center nut just enough to remove the vertical slop.
To recap -
It is important to understand there are two distinct adjustments possible.
The outer rods are tensioned until the spring is able to hold the nose of the airplane at the right height. The right height is when the steering rod is just able to sit at the bottom of the Vblocks. One way to test for this is to bounce the nose of the airplane against the ground and verify that this happens.
The second adjustment is the center rod, here it is important to use additional washers/spacers if necessary in order not to exceed the number of threads available. It is also useful to lubricate the threads with oil to prevent failure of the threads.
With the nose off the ground, tighten the center nut until the entire nose wheel assembly can be pushed up and down and feels loose on the firewall. This is an indication that the spring has been compressed too far and the entire assembly is too short to fit between the Vblocks and the upper firewall shelf. Next, start backing off the center nut until the looseness of the assembly disappears. At that point the spring is just long enough to remove any play. From this point any further retraction of the center nut will increase rudder and pedal pressure.
Video from Swish Projects below.
A Story from one of our customers:
Funny thing – the original bungee on my 701 lasted for years. But with about 5 years and 200 hours on the aircraft, I was persuaded to replace it. So, I ordered one from Zenith, also the bungee replacement tool which helped - only to find the bungee was too big for my plane. It was really loose and with the gear off the ground, I could push the bungee off the pegs on the nose gear leg.
A quick call to Zenith, and Roger kindly digs up a smaller one and sends it to me. It fits nicely, thank you! But, the bugger failed only a year later! Nasty sensation – felt like the prop was going to hit the ground. So I order a new one, and replace it (getting pretty good at this…)
Another year or so goes by, and I’m out in my 701. I land out somewhere in the middle of nowhere (which is kind of the point of having a 701). Taking off, during the 701's trademark ridiculously short ground run, the nose feels a little lower than it should be. But then I’m airborne, so all seems well – for a couple of seconds. Then it feels like it did last time I was flying a twin and the instructor pulled one of the throttles to idle – the plane just starts yawing hard to the right. Full pressure on the left rudder pedal has no effect. An old joke goes through my head – something about being up here for ever if all I can do is go in circles. The plane does seem flyable though, which is obviously a relief – flyable if I don’t try and make a left turn, that is. It’s going to be right traffic today, I think!
Then, as soon as it appeared, the problem seems to go away – only to be followed by the strong smell of burning rubber. By this time I’m less than five minutes from South Lakeland Airport, but I descend to tree-top height and keep over open pasture as much as possible, in case it becomes prudent to abandon ship. I also turn off the fuel pump and have my hand on the ignition switch, ready to transform myself into a glider if I see any sign of fire.
Turns out I don’t need my glider experience with the RAF all those years ago. I land and remove the cowl, and here’s what falls out: (See broken bungee picture)
This explains the stuck rudder as well as the burning smell. When the bungee failed on the left, the remaining part of the bungee tried to twist the nose gear to the right, and then fell and jammed between the gear leg and the firewall. Eventually, it must have fallen out - at which point the rudder freed up – and of course it fell onto the exhaust and started to cook.
You can imagine at this point I don’t even want to see another bungee. I recall something in a Zenith newsletter about a new bungee-less system, so I place a quick call to Zenith. Seb tells me that they have a kit for the 750, but not yet for the 701. But he helpfully suggests chatting to Viking Engines (who do the very attractively priced Honda engine conversions) - they apparently have a “steel bungee” kit. A quick call to Jan at Viking and a review of their site, and I place an order for one.
Meantime, on removing the nose gear in preparation, we notice a crack in the flange that holds the top end of the nose-gear in position:
Luckily, I have with me A&P extraordinaire Ray Torres, who rapidly fabricates some doublers and installs them. His Lake Renegade, which he restored from a basket case, won trophies at Sun n Fun – so you know he’s good at this kind of thing.
A few days later, we install the steel bungee kit, and it works really well. At first try, as shown, the gear only had about 1.5" of travel. Another quick call to Viking and Alissa tells me Jan suggests adding a spacer. They are getting ready for Sun n Fun so she offers to bring it over - that's service!
We added the spacer today, and now have nearly 3" of travel. The kit features a neat pre-load feature so that, when the aircraft is in the air and the gear is resting on its bottom stop, the tension in the spring is removed. Think of it as being able to adjust how far off the bottom stop the gear has to travel before the spring engages.
Anyway, this has the effect of DRAMATICALLY lightening the rudder in flight because the spring is not pushing the gear leg down onto the bottom stops the entire time. The old joke among 701 pilots is that the rudder is "set it and forget it" - the bungee makes it so stiff. But not anymore! The rudder is now as light and responsive as the other controls. Great improvement!
My advice to anyone about to replace the bungee - order one of these kits. You won't regret it.
Seb Dewhurst
”Just finished installing your mod kit on my flying Zenith CH601-XLB, (N601BL). Elapsed install time was 4 hours. Could not be more pleased. I am so glad to be rid of the rubber bungee. Looking forward to first flight after Condition Inspection. Please make sure current 601 and 650 owners know that the install is simple on already built airplanes. “
Bruce Laughlin
Tulsa, OK
1H6
Alissa,
The pictures are out of sequence but you will get the idea. Nose cowls and air filter were already removed for start of Condition Inspection. Took weight off the nose wheel but left the nose wheel steering rods connected. Cut the rubber bungee. Enlarged an existing hole in the side of air filter housing that aligned with the lateral rod using a step-drill bit. Long needle nose pliers and forceps facilitate cotter pin work. Removed pins and slid out lateral rod. Drilled two additional cotter pin holes in lateral rod 1/2 inch in from existing holes for new side plate retention. Fabricated centering tool using 1 3/4 inch hole saw and painters tape and drilled the two 9 mm holes in the firewall top rail. Installed new side plates and the lateral rod. Installed 4 new cotter pins. Installed the rod base, spring and plastic sleeve in top of strut opening and finally attached the top cap. Adjusted top cap and secured nuts with safety wire. I am an A&P and my buddy who discovered this mod kit and told me about it is an IA. He was curious to see how this kit installation went so we did it together. (Why turn down good free help?). I can assure you that there is nothing involved in installing this kit that requires either of those skill levels. Our total elapsed install time was 4 hours. Thanks for providing such a great mod-kit for my Jabiru powered Zenith 601.
Bruce Laughlin
Tulsa, OK
N601BL
