172 Tail Wheel Conversion

[53B]

Hi Folks,

The time has come to start my conversion. I have collected all of the parts and information that I think I need. Still waiting on some field approvals but I'm going to roll the dice and hope that they are processed by the time I'm done. I have provided a link to pictures and progress reports if anyone is interested.



http://www.fullenfamily.com/N9153B.htm

[six.zero.charley]

Cool man, interested to see how easily those mains are switched. Looks like a nice 172.

[djbaker]

Keep posting those pictures. Looks like a great project. I tried to buy a conversion kit but nobody seems to make them anymore. What are you using for a gearbox?

[53B]

Thanks for the encouragement. There's no turning back now!

The main gear box will be all stock 170 parts. I'm using the P-Ponk outboard gear supports which have to be field approved since they are STC'd for a 170 but not a 172.

The STC for the conversion is documentation only. No kit. No parts. You have to go on a scavenger hunt for 170 gear legs and gearbox parts. You have to fabricate the tailwheel attachment from scratch.

The STC is sold by Ron Fravel in Indiana. I don't have his address handy but search these forums and you should be able to find it.

[Jr.CubBuilder]

Neet, that's going to be a good looking plane if the rest looks as clean as those tail feathers. There was a straight tail 172 at one of the local airports, it looked for all the world like a 180 unless you knew what to look for.

[170C]

Your photos sure look neat. Keep them coming. Wow, that tailwheel bracket is long! Mine (Bolen Conversion) looks long compared to a 170's, but yours appears to be 50% longer. Does yours add a stringer in the aft part of the plane? Are you going to use 170 gear or something else?

[53B]

Your photos sure look neat. Keep them coming. Wow, that tailwheel bracket is long! Mine (Bolen Conversion) looks long compared to a 170's, but yours appears to be 50% longer. Does yours add a stringer in the aft part of the plane? Are you going to use 170 gear or something else?

All of the Bolen / Bush conversions that I have seen also use a long plate to span the last two fuselage bulkheads. I would like to see what yours looks like if you can send me a picture.

There is an existing stringer inside the tail along the top row of rivets for the tail wheel bracket. The rivets are upsized to -5 along the top which includes the stringer.

The STC calls for "Lady Legs". I currently have early 170 gear to use until I can find/afford a set of "Lady Legs".

[johneeb]

Two tail tie downs, must be windy in Columbus.

Great pictures. Thanks for allowing us to follow along on your project.

[mod cessna]

53b. Looks good so far. I am doing the same thing right now with the same STC. I have yet to tackle the tail wheel but i am almost done with the main gear install. Here are a few pics of it so far. I would really like to do something different with the tail wheel install but what is approved is approved. Any help i can give ya just let me know. http://pg.photos.yahoo.com/ph/mattvoit/ ... EB.6eYqUIz

[53B]

53b. Looks good so far. I am doing the same thing right now with the same STC. I have yet to tackle the tail wheel but i am almost done with the main gear install. Here are a few pics of it so far. I would really like to do something different with the tail wheel install but what is approved is approved. Any help i can give ya just let me know. http://pg.photos.yahoo.com/ph/mattvoit/ ... EB.6eYqUIz

Cool! Thanks for the main gear shots. Looks like you took a lot of skin off to do that. The main gear installation seems pretty straight forward. Were there any surprises?

The tailwheel at first seemed an impossible task to make it fit and look good. I bought a 170B tailwheel bracket and considered getting a field approval to use it but it doesn't fit well on the 172 and the engineering data would have been cost prohibitive for me to do(1200.00-1500.00). I also thought about forming it out of 2024-0 material the having it heat treated to 2024-T3. Again, the cost was too high for me (600.00-800.00). I finally made a wooden form that was the same shape as the tail and used a 56 oz. dead blow hammer to form the plates.
You'll notice my bracket is shaped a little differently at the back than the drawing shows. I just took the excess material off of the top and add it to the bottom. If you cut those plates to the dimensions shown on the drawing. They probably won't fit with proper edge distance for all of the fasteners. Also, if you don't make it wider at the back, the lower spring block won't be covered by the plates and the two AN4 bolts won't be holding anything. In the end, the installation per the drawing is certainly the least expensive dollar wise and doesn't look that bad when it's done.

Hope this helps!

[mod cessna]

Yes I did notice the shape of your rear attachment. It looks good. It sounds like you had to go through a lot to make it work.
Here are a few things to consider on the main gear.
1. I replaced the fwd side and bottom skins because of previous damage, but the part number 0513006-23 fwd bulkhead angle can only be installed by removing the fwd bulkhead that it is riveted to or by removing one of the fuselage side skins. I know at least on of the conversion STC's have you cut a 2" hole in the side of the fuselage to slide it through. Removing and re-installing the side skin is only a few hour job at the most so I would do that.

2. The STC does not say to change the top gear box cover skin (#40 fig 21 170b IPC) Big mistake! Fist off it has to be lengthened to pick up PN 0513006-23. The 172 skin stops at the bulkhead, the 170 is riveted to the angle only. Also the 172 skin is very thin, I think it is .032 the 170 skin is much thicker.

3. Fwd floor panels (where your feat go) have issues. Be prepared for some fitting issues. I made new ones.

4. P-ponk gear attachments. Work great, very nice product.

Those were the big issues. I will let you know if anything else big comes up. I cant wait to fly this airplane.

[53B]

Yes I did notice the shape of your rear attachment. It looks good. It sounds like you had to go through a lot to make it work.
Here are a few things to consider on the main gear.
1. I replaced the fwd side and bottom skins because of previous damage, but the part number 0513006-23 fwd bulkhead angle can only be installed by removing the fwd bulkhead that it is riveted to or by removing one of the fuselage side skins. I know at least on of the conversion STC's have you cut a 2" hole in the side of the fuselage to slide it through. Removing and re-installing the side skin is only a few hour job at the most so I would do that.

2. The STC does not say to change the top gear box cover skin (#40 fig 21 170b IPC) Big mistake! Fist off it has to be lengthened to pick up PN 0513006-23. The 172 skin stops at the bulkhead, the 170 is riveted to the angle only. Also the 172 skin is very thin, I think it is .032 the 170 skin is much thicker.

3. Fwd floor panels (where your feat go) have issues. Be prepared for some fitting issues. I made new ones.

4. P-ponk gear attachments. Work great, very nice product.

Those were the big issues. I will let you know if anything else big comes up. I cant wait to fly this airplane.

I can't wait to fly mine either. I was hoping to be done in a month, but the main gear installation may take longer than I thought.

I knew that I would have to take one of the side panels loose to get that angle in. I also wondered how I would get that angle tight up against the floor pans where your feet go since they have such an angle to them where they meet the bulkhead.

Is there an issue getting those steel reinforcements under the engine mount carry through straps where they overlap the bulkhead flange? I would hate to have to pull the engine off just for that.

Finally, (for today) do the bolts fit through the holes as they are or will they need to be reamed to fit?

Thanks for the info!

[gilbo]

the picure are great. i was just wondering what size tires were on that plane mod cessna? it look really good. i just got a 175 and hope to convert it to tail dragger. i need to start collecting land gear parts.

[mod cessna]

I knew that I would have to take one of the side panels loose to get that angle in. I also wondered how I would get that angle tight up against the floor pans where your feet go since they have such an angle to them where they meet the bulkhead.

My bulkhead angle all ready had a few holes in it so it ended up being flush with the top of the bulkhead. As it should be. The floor pans can be made to fit by trimming about an inch off the end so it stop where the bulkhead and angle meat. Then putting a bend where it comes up to the angle. Ooops now the holes on the tunnel and side panel do not match up. So i just made new ones. Custom fit.

Is there an issue getting those steel reinforcements under the engine mount carry through straps where they overlap the bulkhead flange? I would hate to have to pull the engine off just for that.

No they go under ok. The problem with the steel reinforcements is they are drilled. The drilled holes just do not match up well at all. It just takes some careful placement.

Finally, (for today) do the bolts fit through the holes as they are or will they need to be reamed to fit?

No. The holes on the outboard attachment are a size smaller(in the bulkhead). It took lots of reaming drilling filling to get the holes to the proper size. You should have an interference fit with the bolts.

gilbo- They are goodyear 26" tires.

[lcranton]

Hi Mark, Last year I worked with a friend and we converted a 1956 C172 to a TW using the Fravel STC. As you have found out the most difficult part was making the TW attach bracket/doublers. We pulled a fiberglass mold off of the tail cone and then made a cement buck. Hammer formed 2024-0 to shape and had it heat-treated. Also had to redesign the brackets for edge distance and proper shape. If you make the parts per the drawing they will not have the proper fastener edge distance. From your pictures the ones you made look great and are very similar to ours. The aircraft was a total restoration/modification. TW conversion, center stack panel (DELAIR STC) new radios, instruments, wiring, plumbing, engine overhauled, SkyTec starter, oil filter and new engine instruments. I did the test flights on a Sunday. It flew great! Got the owner some time in the aircraft and he left that Friday with 5 other aircraft for Oshkosh. Good trip no problems. Returned with 40 hours on the aircraft. Hope you have as much fun; It’s a lot of work but worth it.

Larry