Scott 3200 attachnment bolt

[Lee]

I am replacing the leaf springs on my 1954 -170B. What is the proper size of the bolt holding the Scott 3200 tail wheel to the main leaf spring? I ordered new springs from Univair and bolts from AirRepair ... one being used to attach the leaf springs to the fuselage, the other being a bolt with a tie-down ring ... L-19. The bolt I removed from the 3200 is much larger than the one I received and the bolt for attaching the springs to the fuselage is shorter than the one currently installed. Thoughts?

Thanks

R/Lee Robinson (N1967C)

[GAHorn]

Do you have the IPC for your B model?

The eyebolt for an L19 is PN 0642105 which is an AN7 bolt…but is a bit longer than the original AN7-10 used for the 170B and should have a washer or two added to take up the extended shank length.

The bolt at the top of the stack is originally an AN6-22A…but passes thru a bushing PN 0510000-36. Are you missing the bushing?

[gfeher]

George, the figure from the IPC that you posted is for the Scott 3-24b tail wheel, not the 3200. I make that mistake all the time. The 3200 set up is shown in Fig. 94 of the B model IPC, which shows at the rear-most end of the main leaf spring (where the fork assembly attaches), an AN7-20A bolt (item 5), inside a bushing (item 3, Cessna p/n 0442011-2) attaching the tail wheel assembly to the leaf spring. Univair sells that bushing for $20. Sorry I’m not at a computer where I can post the figure.

[GAHorn]

Gene, I wasn’t posting that pic for the tailwheel …. but for the forward attach bolt and bushing. The 0642105 eyebolt he plans to use is different entirely for the Scott 3200, and requires an extra flat washer or two. Thx.

[gfeher]

Yeah, George, I should have worded my post differently. The figure you posted shows how the leaf springs attach at the fuselage end. Fig. 94 shows how the 3200 assembly attaches to the main leaf spring at the tailwheel end. Extra washers are needed at that end. I had to use 4 AN960-716 washers on the AN7-20 bolt at the tailwheel end on my plane, one under the head and 3 under the nut. If you use an eyebolt instead, I’m guessing that you will need to use a similar amount. But someone who has used the eyebolt will know better.

[Lee]

I do have the 170B IPC and noted the bushing at the attach point in the fuselage ... hope to dig into that one tomorrow. I will check with Univair about the bushing for the bolt that attaches the tail wheel to the main spring. I hope the bushing and the eye bolt will work. Otherwise, I'll just go back and use the larger diameter bolt like I removed, which will require enlarging the hole in the main spring. (I bought a new set of springs from Univair) An interesting project.

[Lee]

Re: the bushing at the fuselage end of the spring stack ... I think I do based on the size of the bolt I pulled out and then temporarily re-inserted so that I could work on the Scott 3200. I'll know once I get the stack out.

Question though re: the bushing (P/N 0442011-2) on the bolt that attaches the tailwheel assembly to the main leaf spring is something I don't have. (My tailwheel assembly was attached to the main spring with a bolt that I think is slightly larger than the OEM bolt) Univair wants $20.00 for it. Curious as to what the bushing is made of and wonder if it can be sourced elsewhere. Fun!

[c170b53]

Humm….the diameter of the hole in your present spring adapter ? An older tailwheel assy I guess, $20 you’re getting away light.

[Lee]

I measured the hole in the tailwheel case at 1/2" ... ditto the diameter of the bolt that was installed attaching the assembly to the leaf spring. The eye bolt I received from AirRepair measured at 7/16". The hole in the new spring is slightly smaller and will have to be reamed or drilled.

Slightly off-topic: I have seen mention made of eye bolts attached to the tailwheel steering arms? My arms are bent up ... never had any issues ... curious though about the eye bolts and their purpose ... improved steering, such as it is?

Thanks ...

[c170b53]

I’m still left wondering why you need to drill the spring, you shouldn’t have to nor is drilling it out a good idea. Could it be a previous owner did away with the bushing and did drill the spring for a larger bolt and as with my previous post, what about the spring adapter. That’s item 4 in the IPC which keeps the tailwheel from rotating about the spring. cessna calls it a spacer but most call it an adapter.
In this graphic from Alaska bushwheels for their product the adapter is depicted as item 4 as well but the detail is better edit a bit better

[c170b53]

Just flogging a dead horse, I guess but in this pic you can see the spring adapter.

Its two edges can be seen to centre the spring in the tailwheel housing preventing rotation about the bolt.

[GAHorn]

I measured the hole in the tailwheel case at 1/2" ... ditto the diameter of the bolt that was installed attaching the assembly to the leaf spring. The eye bolt I received from AirRepair measured at 7/16". The hole in the new spring is slightly smaller and will have to be reamed or drilled.

Slightly off-topic: I have seen mention made of eye bolts attached to the tailwheel steering arms? My arms are bent up ... never had any issues ... curious though about the eye bolts and their purpose ... improved steering, such as it is?

Thanks ...

Jim’s comments (C17b53) are ALL exactly correct. I recommend you follow those exactly. Also, there is a LOT of talk about how to improve tailwheel steering authority on these airplanes….and almost All of them worthless information. Don’t expect adding eyebolts to the steering chains or the up-turned steering-arms are going to make any difference whatsoever.

The primary authority for steering these airplanes on the ground is Brakes.

The main reason tailwheel steering is weak is usually:

1-Incorrect tailwheel mounting-angle. (This has been addressed numerous times. The tailwheel should have positive caster… meaning the top of the king-pin should be AFT of the bottom of the kingpin. I.E., the turntable leading edge is higher than the trailing edge, as depicted in the Scott Assy Dwgs)

2- Loose tailwheel steering chains and cables. They should be “Taut” …not “slack”…..and the TENSION springs should be only slightly stressed in tension….not stretched and not relaxed.

[Lee]

Questions/comments ...
I was able to easily separate the tail wheel hub using a little compressed air and my vise as another post suggested ... the gasket is in good shape.

I contacted Airframes Alaska and ordered a spacer/bushing ($12.50 plus shipping) for the bolt that attaches the tail wheel assembly to the main leaf spring. I found I had an 1/2" bolt (AN8 I think) installed ... will be installing an L-19 eye bolt which appears to be an AN7 ... the spacer/bushing I bought reduces the size of the bolt from an AN8 to an AN7. I will have to slightly enlarge the hole in the main leaf ... the leaf springs, all new, came from Univair.

The tailwheel assembly fit the leaf spring snug as I had a spacer between the leaf and the assembly which did not allow any movement.

However: Question ... I tried to take the nut off the kingpin and the whole pin rotates evidenced by the zerk fitting moving when I apply pressure to the AN320-8 nut (I did remove the cotter pin). I noted the bracket assembly in the IPC (Fig. 94, p154) but, it looks like the kingpin is attached to the assembly. Is the kingpin staked or permanently attached to the tailwheel assembly?

Any thoughts on this?

I also agree about not using eye bolts on the steering arm ... good comments. My steering arms are bent upward and I have never had a problem on the ground ... staying ahead of the airplane and using brakes (conservatively) are key.

Thanks ... R/Lee

[Lee]

Please disregard my last post re: removing the nut on the kingpin. I had a thought and went out and looked at the tail wheel assembly under a strong light ... noted the nut beneath the zerk fitting ... 3/8 open end wrench ... problem solved! Sorry about that ... a good nights rest and a strong light did wonders!

R/Lee

[GAHorn]

Please disregard my last post re: removing the nut on the kingpin. I had a thought and went out and looked at the tail wheel assembly under a strong light ... noted the nut beneath the zerk fitting ... 3/8 open end wrench ... problem solved! Sorry about that ... a good nights rest and a strong light did wonders!

R/Lee

The expanded diagram/sketch (see Jim’s post above) as well as Alaska Bushwheel’s and Scott’s Parts drawings should provide most answers to assy-questions. The kingpin itself is part of the main bracket assy and not a separate item.