Looking for correct drawings for AWB 2500 Skis

[howitzer_flyer14]

Hey guys,

Wow, you fellas are quick with the replies; it's great! I gotta another quick one for you guys. What props are some of you guys using? I have a McAuley 7654 cruise on mine and I'm wondering if it won't be enough "get-up-and-go" for skis. I don't think I'd every gross the bird out on skis, two people max. Just curious on what other folks use since I'm in the market for a trade or purchase for a finer prop.

[mdpesky]

John

What size tires are you using when you have the wheel skis installed? Your photos look like they are larger then 600's? Is there any limitations in that regard, I see no mention of tire size in the drawings? Currently I have 600's on my 170 as we had wheel pants installed on it, will this give us adequate ski to ground clearance when wheels are down(ski's up)?

Does anyone know how large you can go in tire size when running AWB 2500's on the C170B or what size tires you should be running?

The other factor of course is weight, trying to keep it light as possible leads me to wanting to use the 600's, but if the ground clearance is inadequate then maybe larger tires are required?

Any advice appreciated.

Mark

[JohnNielsen]

I have 8.00 tires. Do not know what the requirements are. I chuckle at weight concerns in winter...the skis will add aver 100 lbs, the pump 15, winter clothing and safety gear will add 40, winter fat will be 25...but the DA is so low, that she will still pull just about anything into the air that you can stuff in and on the beast.
John

[ddr36d]

Mark,
I was thinking a couple of days ago that I should check to be sure you got the drawings. I installed my pump on the tunnel & far enough back so the handle doesn't go under the panel. I leave the pump in all the time & just remove the handle when the skis are not on. My handle is 13" long & doesn't seem to take too much force to pump the skis down when on the ground. I have the Fluidyne 3000 Fly-lite skis so maybe there is some difference in pressure. Here are a pictures of my pump & reservoir installation.
Don

[mdpesky]

Hi Don, yes I got the drawings thanks. We're well into the installation now and the drawings are really helping. I'll be making copies in the next two weeks and get them sent back to you. Your pump installation looks good and was the original position we considered. Based on advice from others on the forum I became concerned the lever pressure would be too high for a short 12" lever, looking at your photos I'll have to re-consider if we mount it as you have or go with the pump mounted to the side of the tunnel on the co-pilots side. Your location is for sure much more convenient and preferred!

The job of running the hydraulics and getting the rigging right is a big one, without the drawings its impossible!

Thanks for the photos.....Mark

[mdpesky]

John

With the 8:00 tires how much clearance between the heal of the ski and the ground do you have with ski's in the up position?

Mark

[JohnNielsen]

I put the one ski on just for the pics and will not have them back on for another week waiting for my hydro lines to be made. So I can not provide the measurements you need.

Indeed, after MANY times of placing the pump in various positions to check for interference, then complete dis-assembly of the pump/valve/tank...I reassembled it with one of the lines mis-connected!!! Everything had to come apart and two new 1/4 lines bent and fitted to make it right. Once fit for the first time, it is an easy 30 minute changeover.
John

[hilltop170]

I fitted my pump/reservoir assembly in the same position on the tunnel as Don, it works very well there. It disconnects very quickly, two bolts and two hyd lines. I pump/drain out all the 5606 thru the lines to the skis outside of the airplane before loosening the pump connections, so no messes inside the plane.

I had 25-10x6 baby Airstreaks field approved on my AWB-2500s. Unfortunately, all the paperwork went away with the skis when I sold them. They were great for ground clearance and during breakup with soft ground, never drug a tail except going thru pot holes. Ground clearance of the tails on pavement was about 4".

[mdpesky]

Its decided, we are going with the pump installed on the top of the tunnel in front of the trim wheel, this gives the neatest install with the least cabin infringement. Thanks guys for all the photos and input. As far as the tires, we will start with the 6:00's we have and see what the clearance is, hopefully enough. That said there is no doubt larger tires have big advantages on the rough strips and spring thaw conditions when one might be landing on melting ice and/or snow/mud runways?

I'm wondering now if your rigging changes when you change your tire size being you adjust the cables with both wheels up and down?

Mark

[hilltop170]

Mark-
The rigging actually does not do anything in the operation of the AWB2500 skis and tire size makes no difference except in ground clearance. The positioner determines the angle of incidence of the skis, not the rigging. AWB2500s can actually be safely flown without safety cables as long as everything is working. The rigging is only there as a safety backup to keep the skis from rotating up into the wing strut or pictching down too far in case the positioner fails.

Tire size on the AWB2500 makes absolutely no difference to the operation of the skis as long as the tires do not touch anything. I have seen Cubs with 30" Airstreaks on AWB2500s that worked just fine, in fact, the tires were still below the bottom of the ski when the skis were down and just added to the ski floatation.

When the skis are retracted, the pivot arm rotates around the pivot point until the ski is up against the up-stop on the top of the ski tunnel which mechanically positions them in the up position. When they are in motion, they simply rotate down around the pivot point and the tire does not have anything to do with anything. The positioner keeps the ski in the proper orientation during actuation. Rotation stops when the pivot arm contacts the down stop with the tire being suspended in space, and able to freely rotate. The positioner still positions the skis in the proper place. You will not forget the free tire after the first time you jump up on the tire to add gas and it sticks just long enough for you to put your full weight on the tire before it breaks loose and spins your a## off onto the ground. Hopefully the snow is soft and nothing gets hurt.

One of the worst things you can do to the AWB2500s is to tension the front safety cable such that it interferes with the function of the positioner. From what I understand, there should be no springs or bungees on the safety cables, they are there only to check abnormal ski motion if there is a failure of the positioner.

If anyone wants to install AWB2500s and you don't have the positioner arm that bolts to the axle bolt pattern, or you want to mount AWB2500s on another type of airplane, it is very easy to make. PM me and I'll walk you thru the process.

If you still have questions or don't understand something, PM me and I'll talk you thru it. They are great skis and you will love them.

[mdpesky]

Thanks for the advice Richard, I appreciate it. Your explanation clears a lot of things up!

We are prepping the rigging and the topic came on on best cable size. The old original cables are an odd size of 5/32", a special order size by most suppliers. Does anyone know if its OK to up-size to the more common and stronger 3/16" cable size for the rigging?

Any advice on this will be greatly appreciated, we are wanting to start rigging ASAP so the sooner this decision is made the quicker we can finalize the install.

Mark

[mdpesky]

Everyone/Anyone

Well we hit a snag in sourcing the axle bolts which attach the inner ski axles to the gear legs with the stock Cessna axles. We've tried all the regular suppliers, Avial, Aircraft Spruce etc., none stock these style bolts as specified in the drawings.

The bolts I'm looking for as specified in the drawings are "Inside Wrenching Bolts", allen head style as follows:

4 x NAS 146-60(MS20006-49)
4 x NAS 145-58(MS20005-49)

It does not appear that standard head bolts will work clearance wise on the inside of the rim but we haven't taken the wheel off yet to confirm, this is assumed because thats the bolt the drawings call for????

Can anyone offer advice on supply of these "Inside Wrenching Bolts" Allen style or advice on if a standard head bolt can be used instead?

As usual, this forum has been fantastic for keeping our project going, much appreciated guys!

Mark

[JohnNielsen]

Not much out there for suppliers. This is one I found on Google.

http://www.bandbaircraftsupplies.com/in ... &Itemid=73

Make sure to get the proper tapered washer that is needed go with this style of bolt...and don't install it upside down. Proper torque id also important to reduce chance of failure down the road.

John

[hilltop170]

".............The old original cables are an odd size of 5/32", a special order size by most suppliers. Does anyone know if its OK to up-size to the more common and stronger 3/16" cable size for the rigging?

Any advice on this will be greatly appreciated..............
Mark

Mark-
I think my cables are 1/8" but to be sure, call Atlee Dodge Aircraft in Anchorage and talk to Steve Kracke. He will give you the correct info. They also rebuild and set up AWB2500s regularly. Steve knows as much about them as anybody. At the speed 170s fly, 3/16 " cable sounds like overkill. Don't believe anything Kracke says about me.

[mdpesky]

Hi Richard

I called Steve as you advised and he said its OK to go with the larger 3/16" cable in either galvanized or Stainless(if operating near salt water).

Based on that we decided to go with the 3/16" in stainless, even though we're not in salt water area, the stainless will look better longer and yields a much higher strength then the 5/32" galvanized does.

Now my latest problem, these ski’s have what appears to be the stock Federal rigging that went to the bottom engine mount with a 9/16” size bungee which measures along its inside diameter 16 1/4” long. I’m not sure on the correct math to calculate what the actual diameter would work out too, but my rough measurements across the circle are 5 1/4” (it takes a very slight stretch to fit it over a round 5 1/2” pipe).

The closest bungee I could find was from Aircraft Spruce measuring 4 1/2” diameter but this is too tight, they don’t fit??

Being also they are for ski application, I believe I need a cold weather(CW) version(not sure?)?

Now I'm having trouble sourcing the 9/16" x 5 1/4" bungee, again I've tried the usual suppliers, but this size doesn't match anyones charts????

I reach out again to the group for advice and direction!

Mark