I've got C172G with a Bolen TW conversion, am I've had a pilot friend that told me he felt like there is a gear aliganment issue.

I had a mechanic look at the main gear alignment and he said it does need some adjustment. On the Bolen conversion there is a large stud that goes thru the main gear leg, along with the 4 mounting bolts like most other Cessna axles. The mechanic told me the hole in the main gear for the stud on the axle is too tight of a tolerance to add the alignment shims. He is suggesting we get approval from the FAA and cut off the stud, or replace the axles with Cessna axles. Does anyone know of a reason this would not be ok? The original Cessna design only had the 4 mounting bolts.

Can you get approval to turn down the center a bit to allow for some angle from shims?

It looks like there is a stack of shims in there already? Why can't you just make some shims or buy some Cessna shims and drill a hole in the center.... Don't know if the four bolts are in the same location.

Same set-up as mine, and it's shimmed.

Mine is in the shop next week for gear work and tire changes. PM if you need pics of the parts or assembly.

Gump


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So Bolen had their own gear made for their STC that are different from Cessna 170 or 180 gear legs?

I thought I read that the hole pattern in these was different, but it sounds like it's a leg with a big hole drilled through it.

Might want to check out this link - Looks like Bob & Barb of AVCON have screwed up again. EDIT: THIS EDIT GOES WITH THE ONE AT THE BOTTOM OF THIS PAGE: I was not aware that Bolen had TWO STCs.
The problem STC with AVCON was/is primarily for C175s. In my rush to "help" the first thing I saw was (172) and jumped to a concussion. Apologies here and below for my error.

http://www.askbob.aero/content/cessna-m ... el-kit-upn


Did your mech. put the front wheels on grease pads to test alignment?
Is your tire pressure a match?

Stand 20-30 feet out front to see of plane appears - or is "level" wing tip to tip.
Any hard landings lately?
Might do the same on the side to see if gear legs "line up" on front edge.

Cessna shims are $$$$$$ for each one. They come in several thickness/tapers.

RG - Found another interesting link over where I used to drool some years ago.

http://www.cessna170.org/forums/viewtop ... f=2&t=4330


How long have you owned the plane?
Does it consistently head for one side of the runway in calm air?
Might want to have Mech. inspect workmanship inside the gear box.
Do you have any supporting paperwork for ongoing airworthiness etc.

RGilland wrote: I've got C172G with a Bolen TW conversion, am I've had a pilot friend that told me he felt like there is a gear aliganment issue. I had a mechanic look at the main gear alignment and he said it does need some adjustment. ...

I believe Cessna specifies a very slight amount of toe-in. Look in the Cessna series 100 service manual, it should give you the procedure for aligning the wheels on a 170. Basically, put the mains on greased plates (so the wheels can move freely), load it up (to gross?), then check. There's other methods, with plumbing down & snapping centerlines, triangulating off the tail, etc, but I believe the Cessna manual spells out the quick and dirty method: you put a straight-edge across the front of both tires, and a square off that to measure against the side of the tires, or the wheel rims.

I've never seen a Cessna gear leg drilled like that, with a stud coming out. Is that for mounting wheel-ski's or what? I don't think I'd like that big hole through the gear leg on my airplane. There has been some incidents of Cessna gear legs breaking in that area, generally through the axle bolt holes, and almost always on airplanes which have been operated on skis. There was an AD proposed to require a special inspection on all Cessna gear legs, but it was never enacted.

The amount of load (stress, strain, shear, flexure, bending, whatever) on the landing gear at that location... and the ultra-high temper (crack sensitivity) of spring steel landing gear legs... makes putting a huge hole in that area a really bad idea IMHO.

If you welded in that big axle shaft on both sides of the gear leg, then shot-peened the shit out of it to relieve all the stresses, then re-annealed it soft, and then re-heat-treated the whole assembly back up to "spring steel", then maybe shot-peen it again... then maybe.

Any of the formally trained "genuine article" engineers on this forum can feel free to disagree if I'm wrong.

EZFlap wrote:The amount of load (stress, strain, shear, flexure, bending, whatever) on the landing gear at that location... and the ultra-high temper (crack sensitivity) of spring steel landing gear legs... makes putting a huge hole in that area a really bad idea IMHO.

Yup...you don't want to mess with the spring steel. But if the center bolt is too tight to allow cants to be installed, perhaps .005" off the diameter of the center bolt could work to allow it to go through skewed.

I've got C172G with a Bolen TW conversion, am I've had a pilot friend that told me he felt like there is a gear aliganment issue.

Are you actually experiencing handling issues or is this a perceived problem?

What some might recognize as an alignment issue from the standpoint of operating could be the lack of effective rudder before the tail is raised. At higher angles of attack (takeoff rollout with the tail wheel planted) the P factor will make you feel like your running out of right rudder until you pick up the tail (at least mine does). This is generally attributed to the swept tail.

I used to wear out tail wheel tires real fast. Then I slacked my wheel steering chains (changed to the compression springs from tension springs). That improved my ground handling manners a lot and stopped wearing out tailwheel tires and steering arm bushings where the chains attach to the rudder arms. Just some food for thought.

I have a 172K with the Bolen conversion. I've never owned cessna before this. I didn't realize that the stud in the middle is specific to Bolen and not Cessna. Anyone know why they did it?

WOW, yall reply fast in this forum! Thanks

Let me preface this by saying that i am an extremely inexperienced tailwheel pilot with aspirations of flying AG one day. I bought the plane just to build TW time and work on an instrument ticket along the way to a commercial license.

I purchased this 172G out of OK last year. On the trip home the pilot that was delivering it to me ground looped it. It damaged an aileron and channel, elevator and sprung the left main gear leg. A long story short, i decided to go ahead and buy the plane once it was repaired by a certified Cessna shop in GA. The shop assures me the repairs are correct, however friend with a few hundred hrs in TW aircraft said it was extremely squirrelly on asphalt when he landed it back home. He suggested I have the alignment checked before we do any work on asphalt. It seems fine on grass but again i dont have enough experience to know the difference.The mechanic on the airfield looked at it the other day and said it needed some adjustment. He actually trained mechanics during WW2 so i trust his ability. He is telling me that factory Cessna axles do not have the large stud running thru the main gear leg like what is on mine. This aircraft is the first C172 TW conversion by Ralph Bolen and i dont know if he continued to have the stud run thru the gear leg or got rid of it later on. I dont really want to cut off this stud even if the FAA approves it as from what i hear it next to impossible to get parts for these conversions.

Wannabe:
According to the repair shop that did the ground loop repair, the gear boxes are the strongest well build he claimed to had ever seen.

obxbushpilot:
I need to get more info on slacking the chains as well. I had a new Alaskan Bushwheel assembly put on the plane when the repairs were done in GA. The chains are extremely tight and the mounting hole for the chain is actually elongating.

obxbushpilot wrote: I didn't realize that the stud in the middle is specific to Bolen and not Cessna.

Yup. Mine is exactly the same, and that gear is hell bent for stout. And, it's shimmed so you can adjust the angles.

I cracked the fitting on the left side where the gear exits the fuselage, which allowed the gear to rock aft a few degrees. It wanted to go left on landing like there was no tomorrow, which gave me the one and only time in my life when I got a wheel off the runway and a few inches into the gravel before I wrestled her back.

Once diagnosed, and fixed, this airplane is back to being as docile as a kitten, and tracks true.

Gump

GumpAir wrote:... which gave me the one and only time in my life when I got a wheel off the runway and a few inches into the gravel before I wrestled her back. ...

Wish I could blame my off-runway excursions on the airplane...

It works!

Gump

Oh I tried, it's just that no one was buying it.

I've shimmed a 180 before and couldn't get it right, I took out all the shims and started again and it only took one or two

RG - Found another interesting link over where I used to drool some years ago.

http://www.cessna170.org/forums/viewtop ... f=2&t=4330

Gump and I seem to have good luck with ours. I have read some interesting stories though about certain issues with the Bolen conversion. In the post that Wannabe linked, the OP describes having to change the slacked steering chains to tension springs in order to taxi properly. One BCP member found cracks in the tail wheel mount. Another member from here in AK reported his to be one big expensive mistake and sold it.

This is speculation on my part, but there a few things that will make a person converta C172 to a tail wheel:

1) The owner has more time and money than brains and overlooks the fact that he could get a 170 cheaper and perhaps a 180 for the equivalent investment and pays a shop to convert it.

2) An A&P uses his/her spare time and experience to convert the plane for less than paying a shop to do it, making it a more affordable investment.

3) Someone balked a landing and bent the plane, has a hefty insurance payout and uses the money to pay a shop to convert the plane with this STC that he/she has been reading about on flying forums.

Scenario 3 is what prompted mine (before I owned it, back in the 80's).

The extent to how bad it was balled up the first time (if applicable) and the quality of the repairs are probably the two biggest factors in how satisfied someone will be with the aircraft post conversion. It's probably hard for a firm to get that involved in a project of this magnitude without running into some setbacks like cost and schedule overruns. I found out after I bought the plane that the company that performed the conversion of mine had done this to several aircraft. Maybe mine was one of the first because even after being the 3rd owner since conversion, I had to make a lot of little changes and reworks of some of the ugly stuff like brake lines, gear fairing trimming, rudder cable chafing on the hole through the tail, tail wheel chain conversion and a lot of other quality and workmanship details that were not quite what they should have been, but were part of the original conversion.

Now imagine buying one and having someone loop it on the delivery and sending it to a repair facility to have that fixed. Ouch!

RGililand: (sp)?!?

At the bottom of this link is a printable PDF copy of the naughty STC.
Only sending it in case your log books show WHICH STC was used - a Real Bolen or one of these.

http://rgl.faa.gov/Regulatory_and_Guida ... ht=sa296gl

Hope yours is not this STC # SA383GL

EDITED TO CORRECT THE STC #. Bolen had TWO
This second one was essentially for the 175.
I had shuffled the two copies on original posting. MY APOLOGIES.