Brake pedal installation

I'm sorry I'm so late in updating the blog. I have been very busy!! 6 months ago I agreed to take on a side job for a Gulfstream G3 Engine swap. I am designing a new engine installation for the Right side pylon. This plane will be a flying test bed for the manufacturer of the new engine. I have a hard deadline for complete release of the engineering drawing of Feb 9. Consequently I am slammed for time and the Robin has to take a back seat. That's the bad news, the good news is I have earned enough money to purchase a 4 x 8 x 19" 5 axis N/C router!!!! I am expecting delivery to Houston Texas in May. I can't tell you how excited I am to get this tool. Not only will it allow me to make an exquisite wood kit for the Robin, but it will also make possible my next project. I am going to design and build an all wood laminar flow single place high speed airplane powered by an industrial Suburu 40 hp engine. Speaking of industrial engines, I recieved my replacement engine for the MZ 34 I currently have on the Robin.

23 hp Vanguard Engine

When I get back on the project I will swap this engine for the MZ 34. Stripped down and using a forged billet flywheel this engine will weigh 64 lbs. That will put the prototype over the part 103 254 weight limit. However I anticipate that changes to the wing and landing gear will bring her back under 254 lbs. More on those changes later. I plan on mounting the prop on the flywheel directly. Research has shown that a direct drive should yeild 154 lbs of static thrust. By Mounting the prop on the flywheel side the airflow thru the cowl will be in the same direction as the engines design. I will also be able to mount the engine using the PTO mounting fasteners.

I have finished the new replacement landing gear installation. I fabricated a cover plate that can be removed to service the gear. 

new gear cover plate

 landing gear center cover.

The part 103 Robin will go back toi the original Fournier mono wheel. If a direct drive installation works, the prop clearance issues are such that I could use a non retractable gear. Saving even mode weight.









The existing rudder pedals were removed and modified to add toe brakes. This installation is very clean. Here are some pictures of the installation:

toe brakes

toe brake pedals were added to the existing rudder pedals, The toes brake position is adjustable. I will set the position after I get a chance to sit in the cockpit. The brakes are cble actuated and are modified Go Cart drum brakes.

break cable routing

there is enough relief loop in the brake cables to allow full rudder pedal adjustment.

rudder return pulley

I decided to update the Blog this evening because I received a question from a reader about the rudder return cable design. The main change I would make to this design is to raise the cable attach points to the end of the rudder pedals. This still works pretty good. I like this a lot better than the spring return I used to have. You will notice that the pulley bracket can swivel horizontally. The  fwd pivot hole is oversize and allows the pulley bracket to also rotate up and down. The threaded rod is also the cable tensioner.

 This is a better picture of the return mechanism.














Finally in December it was my privilege  to meet a blog reader from Sweden Dr Jörgen Åstrand. He is Fournier RF4 and Piper Cub Owner and possible a future neighbor here in Texas. It was sure nice meeting up here in Texas. Ironically he was also a reader of my Friend Ed Piper Cub Blog. Only at the last minute die we all realize that he was coming see us both during his vacation.

 Dr Jörgen Åstrand and myself.

KJHKHKJHiu

New Landing gear brakes.

 Hello to all the readers of Kitplanes magazine!!   I was fortunate to meet Dean Sigler at the 2012 Experimental Soaring Associations  Western Conference in Tehachapi California. It was sure great meeting and seeing everyone over the Labor Day week end. From the emails I have received I see that the January edition has already made it to the subscribers base.

The first thing I realized when we went to the airport for the initial Taxi test, is that  I need brakes!!!! For the initial flight my buddy Ed was going to keep me from rolling into other planes and hangers, but in reality that's not really practical.
 With this new Grove spring gear, it quickly became apparent that I was going to have a axle bending problem. The axle is a 4130 steel tube 3/4" x .125" wall. I do not want to heat treat the axle, so I am using the 4130 in the normalized condition. That limits the stress to about 95 ksi in tension and 74 ksi in compression. The old landing gear design tucked up inside the hub and limited the bending moment because the point of load application was only 1.75" The new spring gear increases the cantilever distance to 3.57", That distance by the way is the point the axle is cantilevered to the point of load application which is the center of the hub. When brakes are added the distance increases by another inch.  The gear will almost bend now just sitting on the ground!!! To solve this problem I decided to make a sleeve collar that is 1.24" in diameter at the point of greatest moment. this will limit the bending in the axle back to the original design stress.  I bought some 3.5" diameter 7075-T6 round stock and proceeded to make a ton of chips.

Sleeve collar being turned

Here is the beginning of the Sleeve hub being turned on my Lathe.
This is my faithful 36" Grizzly Bench lathe. I've had this lathe for 20 years, and believe it or not I have moved this lathe all over the country chasing the latest and greatest aircraft design contract!! I'm getting too old for that stuff these days however!!

 This gear design is not only way too heavy, its also too damn expensive. As you can see in the next picture, 8 hours of my life was spent standing in front of my lathe!!
  

Chips and turnings

I filled that trash can 5 times!!
I have decided that the final design will be offered in two options, thanks in large part to all of the letters I have received.  I will offer the original retractable mono wheel as well as an  option  Taylorcraft style internal bungee landing gear.

sleeve collar and axle

This shows the outside of the sleeve collar, the part not shown is a flange that mates to the gear leg. In this picture its very apparent how far the axle would have had to extend. The inside face of the wheel bearing rides on the outboard face of the sleeve. The flange of the sleeve is bolted to the gear with 4 .25" dia bolts. The brakes that I finally adapted are from Azuza manufacturing. I purchased them online from Go Kart Galaxy
http://www.gokartgalaxy.com/

ask for Clint. These brakes are mechanically actuated so I ordered all of the cable , cable ends and fittings. I have plenty of excess cable that I think I can route the cable  to the actual rudder pedals. That will be the subject of the next blog entry.because I haven't designed them yet!!!

inside view of gear leg

The 3/4"l axle is welded to a 1/8" steel plate that is bolted to the inside face of the gear. I had to grind out a small recess at the very bottom of the gear to clear the actuation lever. I also had to flatten the lever and remove the 1/4" offset. The flange of the sleeve is also shown in this view.






  

Cable anchor bracket.

I added a bracket to attach the adjustable cable anchor. All in all this turned out to be a really clean installation. The cable will route along the trailing edge of the gear and will be attached to it with heavy duty nylon tie wraps

Drilling the axle hole

If you were wondering how I was able to accurately drill the 3/4" axle hole, this is how I did it.

New Landing gear cont.

I have finished the gear fitting installation to the fuselage. The first step was to locate the fittings using the gear as a guide. I loosely bolted the gear to the fittings and then located the fittings to the fuselage. Once located I back drilled the through fitting through the fuselage bearing blocks. I made a makeshift drill jig by drilling a 1/4" hole through a 2.5" thick block of aluminum. It was very critical to drill these holes perpendicular to the outer flange so the holes would line up with the inside flange. Normally the inside flange would be left un drilled or undersize so the final hole would open up both flanges. I was betting that I could drill a hole accurately enough so the drill would align with the inside flange.

homemade drill guide

I used to work in Wichita at Boeing Commercial aircraft, they had the most wonderful surplus yard I have ever seen. I bought a ton of forged aluminum block and plate stock. This is just a small little piece. There are commercial drill jigs, most notably the "Egg Cup " design. all of these will work, but I didnt have a 1/4" drill bushing for my Egg Cup. 


After the 1/4" holes were drilled, I chased then through with a 1/2" twist drill. Opening the holes up to just slightly under 1/4" (-.003) I then fabricated eight 1/2" diameter aluminum bushings. The 1/2" aluminum stock is slightly larger than 1/2" (+.002) this makes for a nice tight transition fit between the wood and the bushings. I sanded the outside of the bushings and then cleaned them with MEK.

cleaned bushing and epoxy adhesive

once cleaned, I coated the bushings with epoxy adhesive and tapped them into place. The bushings were made with the center hole undersize (.223") so that on final assembly they will be opened up again to .250" The adhesive is used to stop the bushing from rotating when it is drilled out.

installed bushings

the bolt loads are such that they needed to bear into the wood with greater area, this is the reason there are 1/2" diameter bushings.




The landing gear fitting is square and parallel to the landing gear. The fuselage has a slight amount of contour . The load path from the gear to the fuselage is through a mechanism called "Heel and Toe" The design condition is a 1G breaking load applied to the tangent edge of the tires. This creates a large moment that needs to be reacted by the two outer bolts on the gear fitting. Since the fitting is wider than the bolt pattern, the reaction will actually  be between the edge of the fitting (heel) and the opposite bolt (Toe) . Therefore the gap between the fitting and the fuselage must be filled with a material capable of withstanding compressive forces. The fitting is "Bedded" with a mixture of epoxy and cotton fiber (Flox) . Flox is mixed to a consistency of dough. I spread it under the footprint of the fitting and then installed the fitting. The inside of the gear fitting was coated with mold release wax so the fitting could eventually be released if needed.

flox bedding

once the fitting is installed, the excess bedding is scraped away.

When I installed the gear for a trial fit I saw that the clamp block was deflecting and bridging over the gear. To fix this I designed 4 more bushing that were exactly .003" taller than the thickness of the gear. They would crush to equal the gear thickness after installation

clamp bushings

after the clamp up bushings were installed, the bridging stopped and a more even clamp pressure was developed.

fghdfh

New Landing Gear installation

My new gear finally arrived from Grove Aircraft.I have finished all of the fuselage structural modifications. I have built all of the attach fittings and I have prefitted all of them. The gear is designed to clamp up between two radius filler blocks. The purpose of this design detail is to limit induced bending into the fuselage. If the gear were to be clamped with just flat plates, every time the gear deflected, the gear moment would be transmitted into the truss.

new gear

this is one heavy chunk of metal!! Makes me want to think about a mono wheel again.

attach fitting and radius plate

This image clearly shows the radius plate. The gear is clamped with two 3/8" dia bolts. I plan on silver soldering the bolt head to the inside of the steel fitting. This is so the bolts wont rotate when they are torqued. there will be a 3/4" counter bore in the fuselage that the heads will sit in. There is a slight amount of contour mismatch between the fitting and the fuselage truss. I will assemble these fitting with a bedding of Cotton Flox and epoxy. The primary load direction is in compression, with the exception of the fore/aft braking load .

3/4" counter bores

The area under the counter bore has been padded up such that the width of the gear bearing plate is supported.

The attach bolts that pass through these pads are bushed with a 1/2" diameter aluminum bushing.

After the gear is installed, I will need to fabricate a fabric rib that will sit on the front and rear of the gear. An aluminum cover will connect the ribs and fair in the gear

New Landing Gear

I have been patiently waiting for my new Aluminum Landing gear from Grove Aircraft in San Diego. My friends Mike and Neal Lafrance actually own the hanger next to Grove..  Even with that kind of pull, I still have to wait 8 weeks for the gear. As Robbie explained it to me, its out of his hands because the gear has to go to a heat treat shop 3 times during its construction. I have 3 more weeks to wait!!! I decided that the simplest way to add a landing gear to the Prototype was to attach it to the outside of the fuselage in the same location of the old one. I needed to add some additional bearing blocks and increase the area of the two diagonal stiffeners . Truth be told, I should have done that for the original gear.My goal is to have all of the modifications done and the Fuselage recovered by the time I get the gear. I want to be able to just bolt it in and then flip the plane over.

reinforced gear frame

in this picture the extra doubler on the two diagonal members are shown. all of the vertical loading of the gear is reacted by these members. They also need to react the aft braking load by a heel and toe reaction between the gear fitting bolt and the back wall of the fitting. underneath the plywood is 1.5" of birch plywood bearing blocks. .

outer landing gear fitting

This picture shows the outboard fitting for the new landing gear attach fitting. There will be a narrower fitting that is bolted to the inside of the gear frame. Both plates will be welded to a .125 plate that will act as a bearing plate. I will have two 3/8" bolts permanently brazed to the 1/8" plate. I will counter bore into the birch doubler to clear the bolt head. Sitting on top of the plates will be a radius block. The gear will be sandwiched between two of these radius plates. The isead here is to limit the gear bending moment to the gear itsself. The radius blocks will act like two fulcrums.

Unfortunatly this new gear will add 8 lbs to the Robin and may put the prototype out of the part 103 category. I'm sure with the redesigned wing and the single cylinder 2 stroke engine, Part 103 will still be possible. After my talk on Labor Day, the universal opinion of everyone I talked to was to scrap the 2 stroke and Part 103. My Friend Murry Rozansky who is the ESA Treasurer, suggested that I look at the 23hp Briggs and Stratton Vanguard conversions. After some research, I have decided that this is the perfect engine to adopt. The Prototype is actually perfect for it from a weight and balance point of view. My CG will move forward to 22% at full fuel. 26% empty. The static margin increases by 10%. This engine will be far more reliable than the 2 stroke. I will however fly this plane on the MZ 34.

Just a quick update.

I took the Robin to the Airport for first taxi and I discovered a landing gear design error. I built the gear with a horizontal core of Spruce wood. Under the gear clamps, the wood crushed slightly and the gear released or started to slide out of the gear clamp. This is a basic design flaw and because of it, I have fired the designer!!!!

After I hired me back, I went back to the drawing board and started on an all aluminum spring gear. I will either build it myself or Have Robbie Grove fabricate it up for me.


In the mean time, if you are in the Southern California area, specifically Tehachapi on Labor Day Weekend, you are invited to attend the ESA western conference at Tehachapi airport. My original plan was to haul the Robin out for her first Public showing, but the gear problem took care of that plan. I will be speaking on the Robin design @10:30 am on Sunday.

If you can make I would love to meet any of the Blog followers.

Mark Calder

Final Prep

 

I am preparing for the first taxi and flight test. Its incredible how many little "final" jobs are left. I'm really up against a deadline, I am a guest speaker at the SSA western conference on Sunday Sept 2 at 10:30 am. I really would like to have a first flight before that speech!!!  If you are in Southern California on Labor Day weekends, you  are invited to the conference. I'm looking forward to the opportunity.
I started finishing out the design in anticipation of the first flight, I mean I really started getting serious!! The first problem is the canopy, the fwd hing idea is really bad. There were many reasons to scrap the idea, but the biggest was I couldn't run the engine with the instrument panel installed on the canopy. I finally got the engine running reliably. The gasket for the needle seat finally arrived and once installed, the engine rang smooth through the entire RPM range. I was able to put another hour running time on the engine. She should be fully broke in by now.

New Canopy hinge

I decided to hinge the canopy on the R/H side. I installed a 3 foot long piano hinge and a holding lanyard . The immediate result was to greatly simplify the wire routing. I removed all hardware related to the fwd hinge, and I realized the I needed a second latch for the fwd edge of the L/H side.  The existing design has a latch on the aft end of the canopy, but not one farther forward. I have calculated that there is about 100 lbs of lift on the canopy. To be safe and to keep the canopy from racking I decided to add a second fwd latch.

New fwd latch

 I used the existing latches and modified them for the Left side only. I added a compression spring to both latches so they will normally be fully latched. This eliminates the latch plate I had mounted on the inside of the longeron. I was worried that if I added a second latch plate it would make entry and exit into the cock pit difficult.

Rear latch

Another problem also reared its head and that's the need for a small sliding window to access the latches so the canopy can be locked down. I am adding that window as I write this. I should have it done tomorrow. I am adding the window right above the rear latch.

One of the cool things about being in the small world of aviation, is the small circle of friends you realize you actually have. My Friend Ed was in contact with a Pilot of Erickson Helicopter of Medford Oregon through his blog http://nc35447.blogspot.com/

Erickson was in the Midlothian Texas area setting a huge air conditioning unit on a local Walgreen's Warehouse.  Ed is actually from the Medford region and he had a number of mutual friends with Fran, but when the guys showed up here in Midlothian, the circle finally closed. Erickson has an operation in San Diego at Gillespie field. A few months ago I was there visiting my friends Mike and Neal Lafrance. This is where the circle closes, Fran is very good friends with Mike and Neal. Mike gave Fran a ride in his Luscombe a few years ago.

Fran Tebbe

I invited Fran to sit in the Robin.

If you guys are aver privileged to meet the guys from Erickson Helicopter, you are in for a treat. These are some of the nicest guys I have ever met!! I have to apologize because I am bad with names but another Erickson guy took a "ride" in the Robin

Mr Warren

There is Ed in the background















After the Erickson guys left, I decided to convert the Robin to a two place side by side

Gretta and Gracie

Eds girls Gretta and Grace took a quick ride in the Robin. Believe it or not, we were once this small.

Canopy Lanyard

So the final count down continues, I need to add the side window, finish the fuel door and route the Pitot static tube. Once that is finished, I will do one final assembly to catalog all of the assembly hardware and then break her down and take it to the airport