Improving the standard RAF.

[birdy]

Giday, some here know I own an RAF, and have done a few mods to it, and with all the negative $#@! that gos on on this forum bout RAFs, with nothing about improving them except adding stabs, I thought I'd offer help to anyone who wishs to still fly one.
I know the standard RAF is a pig to fly, and has a dangerously high TL for someone who don't understand the phisics of a PPO. But improving an RAF takes more than just add'n a stab.
It all depends on wot you want to do in your RAF, if you just want to fly S/L then bout all you gota do is add a stab.
But if you want to make it more than just a cruiser, then it don't take much to make it easer to throw around either.
I don't build gyros, just fly um, but if you compared my RAF now to a standard one, it'd like chalk n cheese.

[Now, if some w@nker posts on ere that I'm back'n RAFs, I'll take the first flight to where ever and retype this post on ya forehead.] Or anything else that don't suit the thread title.

 

[KenSandyEggo]

O.K., I'll start it off. Foremost after a stab or AAI conversion is to replace all the rod-end bearings in the control system. There are a total of 10. The ones supplied with the kit are of a poor quality and one breaking in flight will most likely ruin your day. The supplied ones have cracked by mearly tightening the lock-nut. Second is to replace the 2 bolts holding the alternator ears with one long one (grade 8) and don't crank the nut too tight. The rod-ends will then stop cracking at the shaft. Better yet, also replace the 2 rod-ends with Heims as in the control system.

Check your alternator. If it's a "World-Wide," you may as well chuck it before it lets you down....literally. You can get a Bosch at NAPA for a little over 100 bucks and it will last indefinitely.

If your prerotator belt keeps flying off the pulley, you probably have an old pulley without flanges. Contact the factory to get a pulley with flanges.

If you have a carbed engine, at the minimum I would purchase an additional Electroair ignition system and run both simultaneously. There were a bad batch of electronic ignition modules and over 30 failures were documented on Norm's Forum with several tipovers while trying to dead-stick in.

It's 3:05 a.m. and I'm going to bed. I'll post other things you can do to make an RAF safer later, but the above are the ones you should take care of first.

 

[route66]

Ken, Thanks for the advice. I ordered 10 new rod end bearings today from Aircraft Spruce and look forward to any other major flaws you have noticed. I purchased a 1999 Raf kit from another party who had planned many structural and mechanical changes which has left me with a lot of options in my build. I have purchased and installed the AAI mod kit which I am sure was a wise choice. My first question is the kit came with two prerotator systems, the stock cable and a Gresen G-500 hydraulic setup. Does anyone have any experience with using this hydraulic prerotator? I noticed on another post that someone had used a dominator prerotator on an RAF with poor success and low RPM. Which way would you go, the stock shaft drive or hydraulic? Thanks for your opinions.

 

[KenSandyEggo]

Don't know about the hydraulic one, but your photo of the pulley clearly shows the type everyone should have...with the flanges. I have a semi-hydraulic system as far as activation. I still haven't installed what I think is a more effective slave unit, but I still get 200 with the old one. I'll try to get it changed out soon and post the results.

 

[twistair]

Brandon,

Two quick notes on hydraulic prerotator:

1) If memory serves, RAF prerotator teeth gear has a reduction ratio
12:1 (bendix shaft rpm to rotor rpm). This means that motor should
have, say, 1800 rpm for 150 rpm on rotor. According to Gresen charts
(see attached pic)) these motor rpm at it's maximum working pressure
of 2000 psi equal to 4 hp only -
not enough to get 30' rotor to these 150 rpm. In other words this
motor need to have another reduction ratio (bigger teeth gear ring) to
spin this rotor with this motor. It would be nice if anybody wise would comment these calcs.
When I saw this RAF on take-off it was clear that it's prerotation is significantly slower from the very beginning and it takes him more time than we get with flex shaft to gain even 100 rrpm.

2) When I saw this hydraulic installation on this local green RAF I noticed
that the motor isn't attached directly to the rotorhead. It has an
additional bent part which I guess has a short length of flexible
drive inside it. Since there
was no builder at site to the moment I couldn't ask him about a reason
but I'm almost sure that he was aware that motor will hit the mast at
aft rotorhead positions. Did you check this?

 

[paulp]

To Birdy & Ken,

Guys, thank you very much for your posts. I am currently building an RAF 2000 with the new fuel injection and I will take all of the advice that I can get. I do not have the stabilator but I am going to add a stab. Myself and another guy are playing with the idea of a T-tail mod using flying wires similar to the Taylorcraft, Aeronca and Cubs to support the horz stab about mid vertical fin but we are not sure that the vertical fin's structure will support the horz stab. May have to make a whole new empennage. Anyway, any other advice would be very welcome on my part.

Thanks again

Best Regards

 

[KenSandyEggo]

Paul P., I looked into mounting the stab on the vertical fin when I was making and selling stabs. The glass guys figured it was too flimsy to support anything. It's a hollow construction. But that doesn't mean someone might not figure out a way to do it.

 

[cgmg]

Paul P.,

Not to hijack the thread, but my best friend flies a '39 Taylorcraft, what year is yours? Also, he flew down to the factory open house last year, and is going again this year, weather permitting. Have you made that parade yet?

 

[StanFoster]

Paul: Best of luck with your RAF2000. Please keep us updated on your building and flying progress with it.

Stan

 

[paulp]

Howdy All,

Ken, thanks for the info. One of the guys that is looking at it builds aerobatic
aircraft.(The Edge) His engineer is looking at it and thinks that it can be done but will require some reinforcement within the vertical fin as well as the strut wires.

Mark, the Tcraft is a 1945 BC12-D Mod 19. Complete restoration with the Harer conversion. Just now finishing the interior. It's a great machine. And, the answer is yes, I plan to be at the factory flyin this year.

Stan, will do. I have mounted the cabin, engine and gimble head, have fitted the windscreen, green house cap and the doors and the seat tank. Today, I removed the windscreen, greenhouse, tank, doors and the cabin and am preping the fiberglass for paint. I mocked everything up so that I could drill all of the holes and do the finish painting and reinstall everything with MINIMUM damage to the finished paint job. I have ordered the dash faceplate from the factory and hope to have that within a couple of weeks. I'm going to follow Ken's advice and replace the alternator bolts with a single bolt and also replace the rod ends. Just for info, my kit was complete and nothing was missing and everything went together with very few problems. I wasn't too thrilled with the manual and the videos were lacking but overall its' been a good experience so far. In addition, I hope to have some molds for a stab within 2-3 weeks and it looks like I'll mfg my own stab. I still, however, plan to seriously pursue the T-tail concept. I would really like to see the HS in the prop wash. The other folks that are helping are crunching some numbers and think that it may be possible to reduce the size of the stab if it is located in the prop wash but I won't know about that for a week or so. Will keep everyone advised.

Thanks all

Best Regards

 

[route66]

Alex, Thanks for the information on the prerotator. You had the advice I needed. I looked at the picture you posted earlier and could not figure why they had the bent piece to mount the rotator. I checked the system I have and it will hit the mast in certain configurations. Not even close to acceptable, thanks for pointing this out. You saved me a lot of frustration and I will go back to the original stock prerotator. Maybe someone else will have a use for the hydraulic system and will be of use to them. Your earlier posts have been enlightening and have helped me with adding electric trim and better placement of the rotor brake handle. Thanks again for your assistance.

 

[twistair]

I'm glad to be of use, Brandon

Fly fun!

 

[KenSandyEggo]

Well, we finally found a man that's good for something.

 

[Harry_S.]

Hallelujah...or whatever?!


.

 

[paulp]

Ken,

I seem to recall something about a problem with some bearings in the psru unit(from the old forum). I'm old now so I don't remember what the deal was.
And, I wanted to ask Harry or Stan if they had encountered any problems with their psru units in so far as abnormal wear around the pulleys or if they had changed anything from the factory set up.

Thanks for any input.

Best Regards

 

[Harry_S.]

Hi Paul:

I have had no REAL problems other than bearing noise. Every pre-flight...which I overdo; it's essentially an annual insp....I check for expended grease around all visible bearings.

I bought an additional drive sprocket and will have it modified, as Ken has referenced Jim Butler's mod. I bought this sprocket like 3 yrs. ago and still haven't had it done. What I have is still doin' it's job.

You know...if it ain't broke, don't....

 

[StanFoster]

Paul: I have heard of the crankshaft support bearing spinning. These problems were mainly with the older style. Mine came with the newer style and has been running uneventful.

I did have one of the angled support brackets develop a crack. I called RAF and they sent down a blue anodized one immediately. I have put on 150 on the new bracket and no cracks.

Stan

 

[Aussie_Paul]

Stan, you said....

Stan, you said....

....What I have is still doin' it's job.

Stan the first thing that will happen, to let you know it is not doing its job, is the crankshaft will break.

A 1 thou" play means that the crank has to flew 4 thou" every revolution of the crank, and the ej seies do not like to have crank flexing. The earlier ea-81 crank was made out of different material and handles belt prsu's without steady bearings.

The most common engine eailure with a Raf would have to be broken cranks.

There were only 2 Raf styles of sprocket. The earlier ones had 1 bearing and the later 1996 onward had 2 identical bearings. It is the later one that we have all had trouble with as the hours build up. If they had put 1 bearing 2" long instead of 2 bearings 1/2" long it would have done the job. I asked Peter why, and he said that it was the cost of a 1" long bearing. I checked prices and yes he was quite right, but engineering wise it would have been so much better!!!

The cracked bracket is a fairly common problem and tells me that your crank could be about to go.

This is not bashing info it is helpful info!!!!!

Aussie Paul.

 

[KenSandyEggo]

I mentioned on the crankshaft thread that the Butler upgrade is the solution. I can only find the instructions and 1 of the 2 drawings. Anyone have them to post? I sent them to dozens of people.