Kit Aircraft Modifications

I’ve been working diligently in getting the axle spacer program up and running. Thanks to all of you who have come to read about them and who have gone to Cleaveland Tools and put your name on their waiting list. I will have product to them around the 15th of January.

I installed the prototypes on my nose gear today and took pictures to put together an informative instruction sheet. We got lots of good pictures and Mike Lauritsen is going to add them to his order page in the next couple of days.

I am hoping to get he word out to the RV-6/7/8/9 crowd that I have a fix for their problem design as well. It would be very helpful if any of you readers would mention it to your friends and possibly print out the article on my blog to post in your EAA, RAA, COPA and AOPA publications. Maybe even as an article in your newsletter.

The more people hear about this fix the more safe we are going to be. I have heard some real scarry stories about people coming back to land with excessive shimmy and spinning bearings.

Dave

I have been able to take the design for the RV-10 axle spacers and modify them to fit the RV-6, 7, 8 and 9A front wheel. They use the same bearing as the RV-10 and have been having the same problem with the spacers supplied by Van’s pre-loading on the bearing seal.

In this application, I reproduced the same configuration as the RV-10 including the through axle. I am going to be offering these two kits for sale through Cleaveland Aircraft Tools.

Retail price for the RV-10 will be around US$180.00 and the RV-6/7/8/9 will be around US$190.00 as the new axle is included. Cleaveland has not confirmed the final price but this is close. They will be available in January 2009.

The axle will be made of aluminum and will use the same through bolt that is supplied in the kit. The actual spacers will be made of stainless steel with stainless steel hardware. The locking screws that you tighten after adjusting the pre-load will have drilled heads so they can be safety wired.  As well, there is a notch milled into the outer portion of the spacers that fit into the heads of two socket head cap screws. These screws are installed in the yoke and keep the spacers from rotating.

Here are some photos. Contact me at HERE  or submit a comment if you are interested in purchasing these.

Thanks for  reading my Blog!

Dave

For some time now I have been hearing of problems intrinsic to Van’s front wheel design in that there have been instances of wheel shimmy and the loss of preload on the front wheel bearings. My investigation into the problem has led me in a couple of directions.

First, there is the issue of the bearings spinning on the axle and the subsequent damage that is caused to the yoke. Van’s has tried to fix the initial problem due to a spacer that was too thin. At 1/16″, the spacer would bite into the bearing race and start to spin on the axle shaft. The spacer would then start cutting into the aluminum yoke and all bearing preload would be lost. This results in front wheel shimmy and all of its inherent risks.

Van’s tried to fix the problem with a thicker spacer made of aluminum which was 1/4″ thick. This has lead to the second problem.

The thicker spacer now contacts and preloads on the seal of the bearing which is leading to seal breakdown and the resultant spinning of the spacer, galling of the yoke and ultimately seal separation from the bearing. I have seen this personally and it is quite disconcerting.

To understand this all we need to revert back to the design philosophy of the Matco wheel that Van’s uses in many of its home built kits. This wheel and bearing set-up requires a preload to be placed against the cone so that it stays seated in the cup and bears the load of the aircraft. When pre-load is lost for whatever reason the cone can come away from the cup slightly with the ramifications being wheel shimmy, bearing damage and ultimately bearing failure.

The wheel/bearing system from Matco is designed to operate in the following manner:

The bearings are made up from two parts called the cone and the cup. The cup is pressed into the wheel hub and the cone is forced against the cup by the sleeve that is installed between it and the yoke. In this design it is very important that the sleeves that provide the pre-load on the outer steel portion of the cone be of a specific length.

The axle that supports everything has to be just a little shorter than the sum of the wheel, bearings and sleeves so that when the outer bolts are tightened the axle does not mate to the yoke. This allows the compression forces to be placed against the outer portion of the sleeves. These compression forces constitute the pre-load that forces the cone to mate properly with the cup in the hub of the wheel. When looking at the wheel while it is spinning, the seal should be stationary.

Now the sleeves have to make good contact with the steel portion of the cone so that it is forced to remain stationary. Both the steel portion of the bearing and the seal should not rotate if the system is set up correctly. The fundamental problem we are seeing with this wheel/bearing/sleeve system is that the contact with the steel portion of the bearing is not being made correctly.

When the 1/4″ thick sleeve of Van’s is used it contacts the inner 1/16″ of the seal and not the steel portion of the bearing. With the preload on the rubber surface of the seal it deteriorated quickly and the proper preload on the bearing is lost. This sleeve needs to be 3/16″ thick to do the job properly.

Compounding this problem is the fact that the steel portion of the cone that the sleeve contacts is curved. It presents a challenge in transferring the compression force from the flat face of the sleeve to the curved face of the cone. The result of this is the propensity of the cone to spin on the axle. This in turn causes the sleeve to spin on the axle and damage the yoke.

Clear as mud I know but it is important to get technical in this explanation as there are many misconceptions out there right now.

Here is how I approached fixing the problem:

First there needed to be a way of getting a consistent preload on the bearing cone without relying on precise measurements in the length of the sleeves. To do this I proposed that an adjustable sleeve on one side of the wheel and a fixed-length sleeve on the other be employed. These sleeves have a profile cut into the face that contacts the cone that matches their radii. It is cut to the proper diameter so that no part of it can touch the seal rubber.

What this does is allow the axle to yoke joint to be more robust by having a properly torqued bolt on both sides. The adjustable sleeve is both a bolt and a nut with a hole through the bolt for the axle. The head of the bolt rests against the yoke and the nut rests against the outer steel face of the bearing cone. When you loosen the nut away from the bolt it tightens against the bearing and preloads it against the bearing cone. Once you attain the proper preload you simply tighten set screws to affix its preload.

A big bonus to this is that the preload can be set without taking the wheel off. This eases maintenance and allows for quicker adjustments.

The second area I tackled is that of the spacers spinning and causing damage to the inner part of the yoke. Here I decided to have a small round milled out of the flanges of the spacers where they contact the yoke. You measure out from the center of the front wheel bolt hole and drill a hole. You then tap it for a 10-24 socket head cap screw. This screw head nests into the milled half round in the flange to keep it from rotating.

Together, these two approaches should solve the problem with the seals being damaged and the loss of preload on the bearings.

I will be offering these for sale through Cleaveland Aircraft Tools and possibly through Van’s and Aircraft Spruce in the future.

I invite your comments and I will add pictures to this post a little later.

Dave

I saw that there was a listing today on eBay for an RV-10 that has a 600hp Corvette LS7 engine shoehorned into it. I went and saw the listing. What can I say. If this person has designed the firewall forward system in the same fashion as he has built the airframe then I hope he never sells the thing. Especially to someone who doesn’t know all of the facts. Someone bedazzled by the sexiness of having the Corvette emblem attached to the aircraft.

You can go to the listing here and have a look for yourself. I don’t know about you but I don’t think that the side skins of the RV-10 are attached with 1/8″ rivets. All of those clecos are supposed to be silver aren’t they? There’s a whole lot of head scratching going on here!!

I personally have looked long and hard into the Corvette conversion and have had extensive conversations with experts in the field. I even flew out to meet Jack Kane who owns EPI Inc. in Washington state. We looked at the many many many variables in converting an automotive engine to aircraft use and simply couldn’t make the math work out without making a whole slew of compromises. Jack is a pretty smart cookie with the degrees and experience to back up his opinions.

I tucked my tail between my legs and headed home. I will put it very simply. There are precious few alternatives currently available for the person building an RV-10 when it comes to an alternative to the venerable Lycosaurus. This is not to say that there aren’t some exiting developments in the works.

I am working on an engine project of my very own. One that uses a proprietary compressor/effector technology that has been developed by a company in Texas. It will use the Brayton cycle which is the same cycle used in turbine engines but it will use a different and more efficient compressor and effector than the axial turbines used today.

My primary goal is to have the new engine fit into the space that existing Lycoming takes up. No new cowl, no new engine mount. It will directly replace the Lycoming.

It will be able to burn almost any type of fuel. Gasolines, naptha, diesels, kerosenes and bio-fuels. The problem for me is that it is going to take a pretty big chunk of cash to make it happen.

Anyway, I digress. It is a wonderful thing that we can invent and implement these inventions within the framework of the experimental category. It is very important though that we do things in the safest and most professional way so that those who are building the plan-jane version are not adversely affected by the insurance industry and the relentless pursuit of the ambulance chasing lawyers.

Thanks for tuning in. Link to me if you can.

Dave

This is something that you don’t see every day!!

I had a fellow in the yesterday having a look at the fiberglass parts that Van’s sends with their kits. This guy lives, eats and breathes everything composite. From America’s Cup boats to custom canoes for children. I have seen his work and I am glad that he came over.

When we had a moment to talk, he told me that Clamar Floats, whom he does a lot of work for is going to be installing a set of their beautiful composite floats on a Van’s RV-7. Talk about a conversation starter. Apparently this fellow lives in the Pacific northwest and is quite an accomplished float plane pilot.

This isn’t the first Van’s aircraft to receive the float treatment. A fellow from British Colombia installed a set a number of years ago and successfully flew them on a Van’s RV-6. His name was Eustace Bowhay. You can read about his installation by clicking here.

I don’t know about all of you out there but I think that I would have a bit of a hard time with the thought of having to extract my 6 foot 200 lb self out of the aircraft to dock the thing.

Dave

Hello Everyone,

News coming across the wire in the last couple of days is that David Carrigan from Prince Edward Island, Canada has flown the first RV-10 to be built north of the 49th parallel.

I had the opportunity to talk with Dave on the phone the other day as he had seen a post of mine and called to find out where I was in the construction of my ‘10. He hadn’t flown his yet when he called so I would like to publicly say congratulations to him for getting his new bird into the sky.

Dave has what I think is going to be a popular modification made to his airplane. He has swapped out the standard Van’s cowl for the new James Aircraft Holy Cowl. This is a cowl patterned after the successful designs of Ray LoPresti. It has the round inlets that have a significantly smaller inlet area. This along with the engine cooling plenum that they sell significantly reduce the drag on the airframe.

Here is a picture of Dave’s RV-10.

This cowl and plenum have just been made available for the RV-10 but they have been popular with the other models of RV. From the posts that I have observed on the Matronics RV-10 forum there has been some difficulties in getting the cowl installed and the majority of the issues revolved around the lower cowl exit louvers. There seemed to be trouble in integrating the Van’s produced louvers into the new bottom cowl. I have only got this second hand so I need to hear more information on this. I will post any comments I get to this page.

We are all hoping that the speed numbers will be better than the original and that the engine has good cooling. Dave has said that he will post some numbers as he gets more time on the aircraft.

I am working on a way to get you higher resolution photos to you. In other posts I have been able to link to another site but I received this photo via e-mail. I should have it available for you to link to very soon.

Dave

Van’s recently posted a Service Bulletin regarding the modification of RV-10 engine mounts. The problem with the engine mounts is that they will not accommodate certain variants of the venerable (I)O-540, A crossbar that runs near the induction sump interferes with certain models of cold air sumps such as those offered by Barrett Performance.

In the SB Van’s says that “it is the builders responsibility to assure that any NON-Lycoming engine (including ‘clones’) be dimensionally equal to that of the stock 260hp Lycoming (I)O-540.”

Van’s has always held firm on the insistence that 260hp be the limit for this aircraft and there have been some who have increased the performance of the (I)O-540 D4A5 engine through the addition if different ignition systems, higher compression pistons etc. I am unsure as to what the driving factor is for this close adherence to a horsepower rating. Is it weight and balance, VNE, risk of litigation?

It seems to me that the builder should have the unrestricted choice as to which power plant he/she puts in the aircraft. The rules under which we build these EXPERIMENTAL aircraft allow us to put any type of power plant in the aircraft as long as the installation meets acceptable building practices and standards.

It is the pilot who is controlling the higher horsepower engine via the throttle that keeps the aircraft under the VNE speed. It is the builder who compromises when it comes to weight and balance. The heavier engine up front will extort a price when it comes to the weight needed in the rear to balance the aircraft.

As for the litigation, I think that there have been too many instances where the spouse of a pilot/builder has brought a law suit as a result of an experimental aircraft crashing. Wasn’t that spouse in full awareness of the construction of the aircraft and the implicit risks involved? Maybe its me and I just don’t get it.

Van’s is doing it correctly when it comes to producing a kit aircraft. They should offer only one engine mount. The one for which they have done the testing prior to bringing the aircraft to market. Let the market produce the modified engine mount that supports other engines. Then let the builder do the verification testing in a 40 hour test schedule. That is what it is there for.

I am all for making modifications to aircraft. That is what this blog is dedicated to. We need to design test and bring innovative products and processes to help with the evolution of kit aircraft. We will modify them to meet a specific mission. The reality is that the mission is subtly different for every builder out there.

Dave

It is funny how you can have this perception as to how a product needs to be manufactured and then you talk to someone who offers up a completely different and better way to do it.

I had another look at my tail strobe mount ring the other day and was talking to an engineer that has experience in CNC and other manufacturing technologies. Here I was thinking that I would need to set up a bar of aluminum and have a 2 axis CNC milling machine mill the shape out. I would then take the remainder of the bar and simply cut the parts off from it using a band saw. This vision defaulted to my usual way of approaching the manufacture of things I design. High complexity and high cost.

My engineer acquaintance looked at the napkin that I was drawing on and said why don’t you just cut it out using a water jet cutter? DUHH!! Now there’s a good idea. This means that can get the parts cut out for a great deal less money and will therefor be able to pass the savings on to the people who are interested in it.

I should know in a couple of weeks where and when it will be available. I am working on getting a US distributor so that largest market is served well and won’t have to deal with the border and its shipping fees.

Happy Building

Dave

Many builders are talking about installing electric rudder trim. The RV-10 is a very capable cross country machine that could benefit from rudder trim during those long flights. The problem with a fixed rudder trim tab is that it performs best in a narrow range of speed. With the capabilities of the RVs in general and especially the RV-10 there is a need to vary the angle on the trim tab.

I initially heard about trim system that Vic Syracuse installed on the Matronics list. Vic did a very nice job of shoehorning a Mac servo into the rudder on his RV-10. I have heard that you can install this system after the rudder has been built. It takes some careful cutting and the installation of an inspection cover kit but it is definitely doable. The actual flying surface of the trim system is not all that big. It extends from the rudder trailing edge a little more than the width of half a piano hinge. It gives the rudder a more complex look with the control arm extending from the small fairing that protects the exit hole.

Vic did a great job of making it look like it was designed with the airframe. This is always the true test of the person designing a modification.

I’ll post some pictures below for you to get an idea of how it looks and functions. You should be able to click on them and you will go directly to Tim Olson’s site where the higher resolution photos are stored. Thanks Tim.

Have a great time today building and modifying your aircraft.

Dave

Hi there everyone. I would like to thank all of you who are tuning in to hear me talk about my favorite pass time. Modifying aircraft to make them more capable, more beautiful and more personal. I just came from my web statistics utility and I was pleasantly surprised at the increasing number of readers. Thank you. When I started this blog I was sure that I had an audience. I am consistently surprised whenever I check the page views.

I would like to ask that everyone out there who is reading this blog on a regular basis to please let one of your buddies know about the site. I would like to expand the readership to a broad base of pilots and owners. The more people we have reading means that there will be more and more input into the blog.

I would also like very much to hear about any kind of modification that you have made to your aircraft. It doesn’t have to be earth shattering or flashy. It just has to be something that you are passionate about. I will have it on the blog in a flash and you will have that 15 minutes of fame that you have always yearned for.

OK, enough about that stuff. Lets get into today’s topic.

Over the weekend I had the opportunity to work on a couple of things. First is Van’s wonderful, high quality, ready to install (NOT!!!!) fiberglass canopy. The second is a modification I’m making to address a weight and balance with the RV-10.

The RV-10 is a four place aircraft. This is an indisputable truth. As such, there has to be a large CG range to accommodate the range of loads from single pilot with full fuel to all seats occupied with baggage. Van’s built the compromise into the aircraft and in my opinion did a fairly good job. Every aircraft is a flying bundle of compromises.

It has been observed that the RV-10 that Van’s uses for demonstration flights usually has a bag of shot located in the baggage compartment when flying with only two pilots up front. The reason for this is that the CG is right up at the forward limit when in this configuration. It has been noted by a number of RV-10 pilots as well as Van’s itself that the aircraft tends to run short on elevator trim authority in this configuration.

Many pilots have resigned themselves to traveling with some weight in the baggage compartment when traveling light. I got to thinking about this and I just couldn’t resign myself to carrying around extra dead weight. At the same time I was reading about many pilots of RVs that have added wing tip tanks or extra cells in the leading edge of the wing. I’m not a big fan of adding extra tanks to the wing without having them re-tested.

So, one day I started thinking about putting in an auxiliary tank in the baggage compartment. Something that weighs in at about 60 to 70 pounds full would be ideal. The extra fuel weight would be beneficial when traveling with just the pilot and passenger. Something that I think I will be doing quite often.

I thought about my typical missions which will be flying the wife and kids to the cottage and using the plane to travel on business. When we are traveling as a family the tank stays empty. When I am traveling on business in an IFR environment the tank will be full.

Now, how do I do it? I decided that a tank that is in the baggage compartment would have to fit forward under the cross brace and up against the rear passenger seats. In this position, I would be able to tie the tank into the cross brace as well as the floor. I decided that there would be NO tank filling within the cabin so I designed the tank to be filled from the Right wing tank.

I initially was going to have the aux. tank filled from the Left tank. That is until I invited Tom Martin, one of my technical advisers to have a look at the concept drawings and diagrams. The first thing out of his mouth was, “Why the left tank?” I said ” I just picked it.” Tom said that because of the predominance of left hand turns in the landing pattern it would be wiser to have the ability to move fuel into and out of the right tank because it is the high tank when coming in to land. Most pilots will select the right wing tank in the pattern because they want the fuel at the pick-up when turning left.

I had to purchase an Andair fuel valve that had the AUX. position. I wanted to be able to feed the engine directly from the Aux. tank as well as have the ability to transfer in and out of it. The fuel lines run along the center tunnel up near the top and run all the way to a section of the tank that protrudes down through the floor.

I had to modify the baggage compartment floor to accommodate a removable panel that would allow access to an area under the floor where the dual transfer pumps, valves and plumbing are located. I want to be able to remove the tank easily for maintenance (15 to 30 minutes work) so I have incorporated shut off valves into the under floor plumbing as well.

This is the way I see the whole thing working. Normally, you would keep the tank full. I am going to be flying the plane solo a great deal so this is the best situation for weight and balance. If we are going to go on a trip where we are going to be loading the aircraft close to the gross weight , I will fly off the fuel from the aux. tank before the flight and we will proceed with the standard 60 gallons.

This thing is a work in progress. I have the fuel plumbing in from the valve to the floor rib at the front of the baggage compartment. The rest is on paper or is sitting on my work table waiting for my attention while I grind and file and sand the exceptional, high quality fiberglass components so that they will fit what is arguably one of the finest aluminum airframes offered in the marketplace.

I will have more commentary and some photos on this topic as I move further along.

Dave