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Just joined the Fat Avid Club

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Posted

Variety is the Spice of Life!

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Posted

Yes indeed. Thanks again for the hospitality ant Osh Doug! Now how many years will it take to get the Magnum back up and running?

Hopefully not as long as it took to get the Fat Avid going! I really want to get back to a tail wheel!

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Posted (edited)

So when I made the last post I had parked the Fat Avid, unpacked it and was getting caught up from being gone for 3 weeks. When I finally got back to the hangar, I saw a small puddle of coolant on the floor. I took things far enough apart to find out why it was leaking. I discovered that when I installed the larger oil cooler I had not allowed for enough clearance from the exhaust. When the engine shook on start and stop, one of the exhaust pipes was hitting the cooler, which is darted to the radiator. This impact over time fatigued the radiator mounts (duh...) and both broke one of the radiator mounts and sprung a very small leak which thankfully did not show up till I was back from the Oshkosh flight. 

I have looked closely and I never liked the darted oil cooler in the first place, so I am moving it out of there to another location. I have it planned but not done yet. Will post pics when done. I think this will be a solid solution that will not have the same failure mode. And from the way everything else held up in the Fat Avid, I think this is really the last issue to correct before having a SUPER reliable ride! THEN on to the Magnum!

 

Edited by Chris Bolkan

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Posted

Maybe before and after pictures would be good,  then we could see what not to do.  JImChuk

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Posted

Completed the oil cooler move from being darted behind the radiator to mounted at the bottom of the firewall. What an improvement! This setup will be much more reliable. I am getting great temps with the smaller radiator and everything is so much cleaner. Only bummer it the cooler hangs down below the cowl on the passenger side instead of all being contained and hidden within the cowl. But I am willing to live with that for the overall improvement and no more worries about the radiator or oil cooler wearing, rubbing and shaking. I will take and post a few pics.

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Posted

Her are a few pics of the oil cooler install. I moved the oil cooler from being piggybacked behind the radiator to this new location. So much better. No rubbing, no wear and tear, and so much more effective cooling from both the oil cooler and radiator. I plan to put a mechanical flap like I had previously installed on the oil cooler in this new location so I do not have to tape the radiator to keep temps up when it is cooler out.

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Posted

Nice. Did you have to cut the cowl to fit around the support brackets or rods?

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Posted

No change to cowl at all. The cooler is about centered in the open space at the bottom of the cowl. I used construction framing braces from Home Depot to bend up the brackets and bought some 1/8 inch rod to make the support braces.

Since moving the cooler I have to tape over both radiator and cooler to get temps into Rotax acceptable operating range and it is in the 60's. Prolly gonna have to block all of it off in the winter.

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Posted (edited)

Hi guys
I completed the fuselage work on my Fat Avid to allow me to convert from Tricycle to TW configuration. The original builder cut out some of the tailwheel configuration rigging to set up electric flaps. That is all fixed and back to original now.
I'm doing this conversion on a budget so going with stock bungee setup for starters. I have a set of stock Magnum gear legs that are much heavier duty and a couple inches taller than the gear legs for the smaller Avids. They fit perfectly on the Fat Avid's wider fuselage so I am excited to try the combination out.
I am also starting out with a stock configuration tailwheel spring setup as opposed to a fancy shock absorbing setup. That would be nice, but out of my budget for this conversion. I have a decent pneumatic tailwheel assembly for an inch and a half spring.
The Fat Avid tailwheel spring perch is an inch and a half wide and has two 5/16 mounting holes that measure 2 3/16 apart.
I am trying to figure out what tail wheel spring to use and where to get one
Any ideas or suggestions?
Thanks!
Edited by ChrisBolkan

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Posted

I’m using the long leaf of a Super Cub spring on my MKIV not sure what the measurements are but I can check it out if you are interested.  The original one was not true spring steel and I had to arch it several time before I replaced it.  Let me know if I can help.

 

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Posted

I’m using the long leaf of a Super Cub spring on my MKIV not sure what the measurements are but I can check it out if you are interested.  The original one was not true spring steel and I had to arch it several time before I replaced it.  Let me know if I can help.

 

Hi! Yes I would like any help I can get. If you can give me an A/C Spruce our Univair number that would be a great start. There is a possibility I can get a Magnum leaf set from a fellow on the Facebook forum. It has the right bolt pattern, but when I had my Magnum I noticed the same characteristics about that spring set as you noticed (that it kept going flat) and eventually replaced it with a straight stinger spring. However, My Fat Avid is not near the GW of the Magnum so it would probably hold up.

So you are using only one leaf of the set? Your MKIV GW is 1150 right? My fat Avid is 1250. I'd be concerned that one leaf might not hold up, but it sounds like a good way to go if yours is holding up well! 

Thanks!

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Posted

So my spring is about 1 5/8 wide with a single hole at each end and yes it is the long leaf of a three leaf spring. Not to sure if this is going to be any help.  Mine came from Backcountry Super Cubs. If I remember right he had the spring made here locally.  I looked for the rest of the spring (other two leaves) but did not find it.  As far as the single leaf not being enough for your plane I would think that would depend on what the weight on your tail wheel is.  If I remember right the MKIV mine is about 65 lbs.  I will check with Bruce BCSC and see if I can find out more about his springs but you may be able to get a local spring builder to make exactly what you want. 

IMG_0265.jpeg

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Posted

I’m using the long leaf of a Super Cub spring on my MKIV not sure what the measurements are but I can check it out if you are interested.  The original one was not true spring steel and I had to arch it several time before I replaced it.  Let me know if I can help.

 

Hi! Yes I would like any help I can get. If you can give me an A/C Spruce our Univair number that would be a great start. There is a possibility I can get a Magnum leaf set from a fellow on the Facebook forum. It has the right bolt pattern, but when I had my Magnum I noticed the same characteristics about that spring set as you noticed (that it kept going flat) and eventually replaced it with a straight stinger spring. However, My Fat Avid is not near the GW of the Magnum so it would probably hold up.

So you are using only one leaf of the set? Your MKIV GW is 1150 right? My fat Avid is 1250. I'd be concerned that one leaf might not hold up, but it sounds like a good way to go if yours is holding up well! 

Thanks!

Have you seen this site? You might give them a call and see what they have that might work for you.

https://www.univair.com/piper/piper-pa-25/view-all/u64079-005-univair-tailwheel-leaf-spring-fits-piper/

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Posted

Hey Chris I had been buying springs from any number of local leaf spring vendors and they just didn't last either too hard and would break or soft and needing constant re arching till they finally broke or I gave up on them. Went back to the single leaf aircraft spruce home builders spring modified/ shortened to suite my avid how I wanted and it is holding up way better then any of the previous springs I was working with. It was way more money but it is proving to be superior in durability. 

https://www.aircraftspruce.ca/catalog/lgpages/leafsprings.php

You could cut and modify 2 leaves into a dual spring setup possibly. I typically have 57 pounds on the tail with the plane in the weight/ balance orientation with the single leaf. These springs have really gone up...

acs part number 06-14500

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Posted

Hey thanks guys!

I was looking at the homebuilders spring and considering it. A fellow on the International Avid site has a Magnum leaf set he said he would sell me. The Magnum spring set will fit exactly. Hole sizes and everything. But I remember that the same dual spring on my Magnum went flat and had to be re-arched multiple times until it eventually broke. I ended up going to a stinger type spring. Anyway, I am going to try the Magnum spring setup on the Fat Avid which is a much smaller plane. Hopefully it wont sag under the lighter load, assuming everything works out and I actually get it. 

If I don't end up getting it, or it fails and loses arch, I will try the homebuilder spring.

I have been talking to Univair. Very nice people, but all that has happened so far is I give them a spring part number and the spring is either wider or narrower than 1 1/2 inches. We've gone back and forth several times, but they have to go measure when they have time and get back to me. That could lead to a solution eventually, but for now I will hopefully try the Magnum spring set followed by the homebuilder spring followed by Univair. At least I have a path(s) forward now. Thanks!

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Posted (edited)

I looked a lot at the Univair site and kept coming back to the Cessna 170 main leaf spring being 1 1/2 wide and looking like it has the best bend geometry for my plane. I found a main leaf used on BAS aircraft salvage for a very reasonable price. They actually had another Cessna spring that matched the main leaf bend but was shorter and 3/16 instead of 1/4 thick like the main leaf. I ended up buying both as they said I could return what I did not use.

I plan on trying the main leaf only and if it doesn't look like it will hold up, I can stack the two. The Cessna has 4 leaves stacked. I will have to drill the spring(s) to match the Avid bolt pattern on the spring perch, but that won't be a problem. 

I attached pics from the Univair site of the entire leaf pack and what I bought used from BAS.

 

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u170AB__98357.jpg

Edited by ChrisBolkan

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Posted

Spring steel can be drilled of course, but some things make it easier.  Don't make a pilot hole first as that hardens the steel .  Drill with a drill press with a new bit at slower speed and plenty of pressure.  At least, that is what I read before I tried drilling tail springs, and it worked for me.  JImChuk

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Posted

Thanks Jim! 

What I have done in the past is use carbide concrete bits. They cut through spring steel like butter. You don't get the most precise hole but it sure does work well! I can't remember where I learned that but it is one of the coolest random tips I have ever gotten. Might have been off YouTube.

Chris

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Posted

Wow the springs got here today and it looks like they will work perfectly. I'll post pics when I get it put together. Might be a week or so till I actually get it done.

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Posted

Coming along on the Fat Avid trike to TW conversion. Magnum main gear legs are fitted and look like they are meant to be there. Inch and a half axles Cessna wheels, double puck brakes. It's a little heavier than I thought it would be, but not too bad I suppose. It should hold up to moderate abuse. The tail wheel is a 2.8-X4. Not super wide but should roll over stuff pretty well. I have a bigger tire and fork for the tailwheel, but I had shimmy issues with it on my Magnum. The tail wheel spring is the bottom 2 leaves from a Cessna 170. The geometry looks good, but I won't really know until both main wheels are mounted and weight is distributed where it will end up. Here's a couple pics.

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Posted

Chris been following your rebuild for sometime.  I was going to suggest a Bearhawk style tailwheel,  but it looks like you definitely have one that's extremely similar. 

Scott in wv.

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Posted

Hi Scott, indeed it is! Iron designs TW built by Scott Weinberg used on the Bearhawk!

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Posted

Since there are complaints about low posting................................ I'm going to start out with the same main tires I was running in the tricycle configuration before running the 29s. I don't want to wear the really expensive tires until I have everything up and running the way I want and have some time driving it. So far there haven't been any real gotchas or anything like that, but it is taking longer than I hoped to get everything set up the way I want it. I also had to convert to manual flaps so made up a flap handle and friction stop to replace the electric mechanism that had to be removed because of the conversion. Not in the pics is that I have the double puck calipers also mounted up now. Progress.

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Posted

Looks good!  stay at it and it will be flying soon.  JImChuk

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