Do you have any idea on price range for the finished product? I'm hoping it will be less than the $15k that stoots wants for a tailwheel stc

Fittings look top-shelf. Well done-

Jeredp wrote:Do you have any idea on price range for the finished product? I'm hoping it will be less than the $15k that stoots wants for a tailwheel stc

Thanks for the nice comments guys, I appreciate it. I can honestly say I could have designed and built a brand new small experimental airplane in less time than this gear project has taken.

My conversion kit will be significantly less money to buy than the other currently available option(s). No figures yet, sorry for the mystery. More importantly, it will require far less time and dis-assembly to do than it required before. I have not looked in detail at any of the other options, so I cannot say how much less time compared to the other options. Anyone who has any detailed information on how the Bolen, Stoots, ACT, Bush, or any other conversion is done, please feel free to post it or PM me, and I will post whether my method is easier, faster or not.

I have now verified fully that no fin or tailplane removal will be necessary, in addition to my previous comments on not needing, wing, strut, boot cowl, or engine removal. This alone adds up to 20 or more hours in de-rigging, dis-assembly, re-assembly, and re-rigging.

Right now I'm trying like hell to find a way to have the integral brake fluid passage drilled inside the main gear leg. I may not be able to do it.

I'll have to start this with an apology, progress has been slow. But I reached another milestone last night, having finally test-installed the sixth prototype tailwheel mounting system. I know at least a few people are interested in any significant progress on this conversion. This one is the final configuration, I drilled the holes in the airplane last night

The last photos I posted showed one of the cantilever leaf spring units (same principle as the 170). We abandoned that in favor of something that is easier on the aircraft structure, and does not put large loads on the fasteners, and does not put that 60 year old rear fuselage casting at risk of cracking. This system approximates the Cessna 180 method of a forward attach, a pivot at the rudderpost, and a longer "bow" style spring.

These photos show the wood mock-up of the spring. The actual unit will be 7075-T6 aluminum. To keep the cost reasonable, and to make the fuselage structure less complex, it will not be a round spring like the 180 but a tapered rectangular cross section. Most of it will be underneath a protective and aerodynamic fairing. It will be a hell of a lot prettier than the 170/L-19 springs

I'm going to try and figure out how to post the !)($#*$ photos, but I've never had any luck actually accomplishing that. Stay tuned for "are you smarter than a 5th grader: internet photos" episode...

Hi EZ,
Congratulations on the forward progress. Just wondering, would you see this tail spring as a potential upgrade retrofit to existing 170s as well? Just idle curiosity, but what do you think?
-DP

Don't think it would fit exactly the same.

There are subtle differences between the back end of a 170 and 172. There would probably have to be a very similar (but not exactly the same) custom version. It wouldn't be difficult, but it would have slightly different shaped parts to account for the different rear fuselage "rudder post" casting, and some minor angular differences in the taper of the fuselage structure.

Also since the stabilizer is different (round versus straight), the distances between the forward stabilizer mount bulkhead and the rudder post MAY not be the same.

But, all that said, essentially, if I had the last three feet of a 170 rear fuselage in my shop, I could make up the custom fitting without too much blood and guts spilled.

Progress!

I am trying to figure out how to get the the !(#*$ pictures off my !(#*$ phone and into the @!($*^ computer. I'll have one of the young geniuses at the phone store help me tomorrow. I know, I know... worthless without pictures!

Today I brought home the first prototype set of custom designed aluminum main gear for installation fit/test. They're gorgeous! We used an early 180 as the model for height measurement, meaning we designed it to sit as high off the ground as a '54 180. This would fit very well with the long-held preference of 170 and 172TW owners to use early 180 gear for back country flying. These are almost 6 inches longer than the stock 170B gear. HOWEVER, these gears will not be as stiff and harsh on the airframe as 180 gears. It will be the best of both worlds. With big tires, this gear will create one awesome looking back country machine.

We made a decision to have the aluminum prototype gears manufactured with the semi-airfoil shape from the start. This is the best balance between reducing drag and reasonable cost,a nd I believe most everyone will want this option. I might offer a cheaper option later, of selling the conversion kit with the un-airfoiled slab gears, but they will not be as light. OR as sexy!

The brake line is also gun-drilled into the main gear legs. This option will be on all of them, because it's a rough field safety issue as much as cosmetic.

Each landing gear weighs 29 pounds. I'll compare this to the 170B leg weight as soon as I can bring a decent scale to the shop. We're guessing that there will be a 23 pound savings in the main gear legs alone using aluminum. Yes, I briefly thought about Titanium, but it is simply the wrong material for this application and way more expensive.

Like I said, I will try to post photos tomorrow, these are bad-ass serious looking gears.

If you get tapatalk its really easy to post pics from your phone straight to the forum.

This is the final tailwheel mounting parts installed... will try to post additional photos in this post over the next few minutes:

Forward stabilizer bulkhead reinforcement, forward tail spring retainer bolt, and safety stop arms (prevents spring from disengaging out of mount):



Final (Final!!!) rear tailwheel pivot mount, 1/4" welded aluminum for durability in hard service:


Wooden tail spring mock-up mounted in fuselage showing forward and rear mounts:


Almost final configuration of tailwheel spring design (we eventually had to shorten the length of the wood spring mock-up because it would flex too far and whack the rudder) :

I have been in his shop and have personally looked at all the main gear fittings. If I had a 172 and wanted to convert it I would go with what Bill is doing. Good job.

When you get this project done, will you be doing it for 175's and 182"s?

Tim

Tim, does Tipsy have her tailwheel endorsement?

Gump

A1Skinner wrote:If you get tapatalk its really easy to post pics from your phone straight to the forum.

Also, review this: https://www.youtube.com/watch?v=o1bq9hmChmk

It can be found in the Base > Help section, which is under development.

I know zip about metallurgy, metal stress, or any such esoteric things, but man, those pieces and parts look brute! Nice!

Cary

I was thinking the same thing Cary; those fittings are beefy. I like it.

Yes, the intention is to have this also available for the 175 and 182. The initial drop tests will be done up to 175 weights. The 182 will likely need one size thicker main gear legs. The beefy looking main gear attach fittings (previous posts in this thread) are designed to serve as a replacement for the Cessna fittings, which are apparently all the same up to the 185. They're 4130 welded fittings.

The tailwheel attach system is welded aluminum, which means it had to be 6061 alloy, which means that it has to be 1/3 thicker than if it were 2024 alloy. The "engineering intent" was to take out all of the bending and twisting and bowing loads before they got to that brittle 60 year old casting at the rear.

This was complicated by the big hole we had to cut in the lower skin, in order to get the tail spring mounts and tools into the fuselage. So the equation had to be solved for stiffness even more than "strength". Those long doublers running forward along the fuselage replace the 170/L-19 "alligator" fitting and the diagonal stiffener angle. They're .080 2024-T3, and the run all the way to the forward stabilizer bulkhead. As a matter of fact, after much head-scratching and cursing, I found a way to cut a smaller hole on the next airplane, reducing the loss of original structure even more.

The girl at the AT&T phone store gave me bad instructions for getting the main gear photos off my phone. Still trying... it'll be worth the wait.

EZFlap wrote:
The girl at the AT&T phone store gave me bad instructions

Yes, I learned that excuse from Gump and it still workes.

Tim

Beefy is good if used in the right way, like these attach points, but remember that the springs used have to be appropriate and optimized to cushion the airframe as much as possible to prevent transferring stress to unintended places. For that reason, I'd say the gear legs should be specific for the weight of the aircraft. I knew a guy once that found out he had 185 legs on his 170, and it was a rough ride, probably not doing old rivets any favors. On the other hand, the original 170 legs were far too soft and caused weird camber issues with the tires when loaded.

You're probably much deeper into the engineering of these problems than I ever will be, but that's my $.03.

The main gear springs themselves are indeed sized for the weight of a 2250 pound 172 and a 2350 pound Cessna 175. Same for the tail spring. If and when we add the early 182 (2550 lbs.) then the springs have to be thicker.

I'm making an assumption that some people use the 180 and 185 springs on 170/172 's mostly to get the extra height, and they just accept the stiffer ride as part of the deal. This is exactly the wrong thing to do, because of the 60 year old rivets and tired structures you mentioned. This is also part of why I went to a straight tail spring instead of a curved, draggy one... it will allow a slightly higher AoA on the ground for better STOL takeoff.

The new main gears in this case will deliver the height of a 180, but not the extra stiffness. The over-kill/over-stiff/nuke-proof stuff in this case is limited to the mounting brackets, so they can take the abuse and not twist or flex... sending that abuse into the airframe. Mostly it's the main gear outboard fitting that has been over-killed, to prevent the repeated impact hammering damage ("brinelling" for the engineer types) that is commonly seen on the upper edge of the gear slot. This is the damage that is shown so clearly in the OEM outboard gear box photos on the PPONK website. The fact that this damage was actually done by the shims (being pushed upward by the gear legs) is amazing. The Cessna style shims above the gear will not be used in my version, specifically to prevent this hammering. This is also why the new outboard gear box fitting has ten times the surface contact area as the OEM style.

I have to admit that the stress paths, flexural properties, semi-monocoque structure theory, stress/strain/yield, Young's modulus, and all the metallurgy that goes with it, is above my head. Please trust that a very very highly qualified aerostructures engineer looks at everything I propose to build, and cheerfully tells me when I have overlooked some shear or tension load that I did not see with my uneducated eyes.

The AT&T tech help phone line cost half an hour of my life, with no resolution. The LG phone device tech help line cost another half-hour, until he simply said that I had to buy a micro SD card to put in the phone, then I could get my photos out of the phone. All this after I damn near died from Monoxide poisoning on the drive to get the gear legs yesterday (really), and then had to do an emergency field repair and build redneck air conditioner on the outside of my minivan to complete the trip. Jeez, the things I get myself into...

Glad you're actually doing some research and development, as opposed to just slapping something together.

As to 180 gear on 170s, you have to bear in mind that there's 180 gear, and there's 180 gear. Different years had different gear legs.

All the 170 gear legs would have been appropriate on a 140, barely. Way too much flex, and not enough beef. The "Lady Legs" were a LITTLE better, but still not there. And, no, the main point of going to 180 gear was never to get more ground clearance, it was to get stiffer gear. The 170 gear just had too much flex, even on airports.

And, the 170 tail spring was worse.

The very early 180 gear legs, as in 1953/54 had just about the perfect (in my opinion) spring rates for a loaded 170B. That's what I had on my airplane, and it was near perfect in my opinion.

Oh, yeah, and it offered a little more ground clearance.

MTV

Re the phone pictures. Don't you have a cable that allows you to plug your phone into a USB slot on the computer? When I do that with my iPhone, a window comes up and treats my phone like it's a storage device, and I can then just transfer the pictures on the phone to the "my pictures" program on the computer.

And that, ladies and gentlemen, is the total extent of my knowledge on that subject. Z, you need to help Bill!

Cary