PSRU Belt tracking - Sparrow Hawk conversion

dunc

RAF/Sparrowhawk/SC 2.5 FI
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My PSRU belt is trying to slide off the pulley towards the outside. Only the end support bracket keeping on. How is this tracking adjustred?
 

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eddie

RAF, turbo subaru 230hp
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DSCF2061.JPG Rob take a close look at the picture I sent you and you will see the plate on the upper pulleybetween the belt and the prop hub.
 

dunc

RAF/Sparrowhawk/SC 2.5 FI
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Not sure I see what you are describing. Does this "plate" create a circular outer lip on the upper prop pulley? Is it black?
 

eddie

RAF, turbo subaru 230hp
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Yes it barely shows its just slightly higher than the belt and has a slight taper to the upper inside edge,which you cant see. it
looks like a end cover for the upper pulley
 

dunc

RAF/Sparrowhawk/SC 2.5 FI
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Sadly the Sparrowhawk pulley does not have this feature. :mad: I'd still be disturbed that it was trying to crawl off the pulley.
 

eddie

RAF, turbo subaru 230hp
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You will . need to have one made take a good look at your prop setup it may be there.
am pretty sure that's its a RAF piece not a warp drive one.
 

dunc

RAF/Sparrowhawk/SC 2.5 FI
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Now I feel dumb. I had not installed the propeller while I did some initial engine fuel and system tests while sitting in the hangar. Hanging on my wall is the used Warp drive prop and PSRU spacer which has the beveled lip. I will now need to reset the belt pulley location and re-tension, then install the prop with the lipped adapter. Good! I will begin my taxi tests later today. Need to install the new ceiling hoist before assembling/mounting main rotor and do a hang test.
 

N447MR

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eddie;n1135829 said:
Yes it barely shows its just slightly higher than the belt and has a slight taper to the upper inside edge,which you cant see. it
looks like a end cover for the upper pulley
Hi Eddie-
I have my air command with the 2.2 on it as you may know or remember. It has a Don Parham PSRU on it which, as I understand it, is what RAF used for their design and looks real close to what you have although no lip on the top. If I remember right, I need to loosen the castle nut on the front of the top and (with the prop removed) there is a nut inside the top pulley that will tighten the belt. Then, I thought that the allen screw at the top and just behind the castle nut was used for tracking the belt. Is this right? I thought I was told that the belt naturally walks the pully back and forth at different power settings, but messing with it yesterday I didn't see any movement at all a different throttles.

My belt has decided to start wanting to move rearward. It moved a lot yesterday with no other apparent changes to anything and made it look like the picture. Belt tension seems okay, but moving that allen screw didn't do squat. How do you properly adjust this thing? I was going to fly to mentone and figured I'd find someone who knows, but with this new movement, I'm grounded. :(

Also, where do you guys get new belts. I can't find any like what I have on mine. Also, Also, the PSRU has about 275hrs on it.
 

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N447MR

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So I talked with Don Parham, and apparently there are a couple differences in what RAF took from him and his original design. He has a tracking adjustment done with the allen screw pictured in my post to angle the sprocket up and down. RAF uses those push tubes to tweek the sprocket assembly. I don't know why it did what it did to me yesterday, but I'm gonna go through the adjustments and see if something just got loose. Still need to find a belt though.
 

eddie

RAF, turbo subaru 230hp
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Actually the belt stays on track by virtue of the 2 end pieces on the upper and lower pully,the bottom

one is on the inside and the upper on the outside,the belt can't move in either direction,also there is

no rubbing of the belt as the end pieces are moving with the belt and pully.And as for using the

upper motor mount tubes for adjusting the track on the RAF I have never heard of that before,and

I don't think that would even work the plate that the upper pully is mounted to would have to flex and that's

not possible to do with the upper engine mount tubes as the whole engine is mounted on rubber.And if

you could get it to flex it probably would crack from the stress. I buy my belt from Amazon.

There is one other thing about the RAF drive unit that should be mentioned,the cross bolt that holds the

drive unit in place should only be hand tight just snug it down don't put a lot of pressure on it as the plate

could crack,the three bolts on the collar will hold the drive from slipping its belt adjustment.
 
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N447MR

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eddie;n1135911 said:
Actually the belt stays on track by virtue of the 2 end pieces on the upper and lower pully,the bottom

one is on the inside and the upper on the outside,the belt can't move in either direction,also there is

no rubbing of the belt as the end pieces are moving with the belt and pully.And as for using the

upper motor mount tubes for adjusting the track on the RAF I have never heard of that before,and

I don't think that would even work the plate that the upper pully is mounted to would have to flex and that's

not possible to do with the upper engine mount tubes as the whole engine is mounted on rubber.And if

you could get it to flex it probably would crack from the stress. I buy my belt from Amazon.

There is one other thing about the RAF drive unit that should be mentioned,the cross bolt that holds the

drive unit in place should only be hand tight just snug it down don't put a lot of pressure on it as the plate

could crack,the three bolts on the collar will hold the drive from slipping its belt adjustment.
I assume you're correct of course, but how can the belt not rub on the end flanges if it it up against them? Because they are turning also?
So no tracking adjustment on that PSRU at all then?
Have you ever had to change your bearings?
Last one:
I looked on amazon and found some that were $20 or so, but they weren't name brand. Now I'm not a name brand guy, but a bad belt would be a potentially bad day so I ordered from grainger for $80 a piece. What are your thought on that or what brands have you used on amazon. He likes the two belt 880850m two belt set up on mine to get a total of 100mm in width.

Thanks for the help.
Geoff
 

eddie

RAF, turbo subaru 230hp
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That's right the belt and the end plates are turning at the same speed,I have never thought about track adjustment,I use goodyear belts however the name has been

changed to contitech hawk as continental tires bought the goodyear line of rubber products buts its still the same quality,My belt is 3 3/8" wide(85 mm),

and I paid $120 for the belt,I have never changed my bearings and have about 800hrs on them,I changed the belt at 400 hrs.My Subaru engine is producing

230 HP and I swing a 5 bladed 68" prop pitched to 14 degrees and so far the PSRU has been good.
 

dunc

RAF/Sparrowhawk/SC 2.5 FI
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1967 Turbo/RSTOL/VG Cessna 185 Skywagon, 1946 Grumman TBM Avenger
Total Flight Time
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I bought my RAF/SH with 660 hours TT. All the PSRU and PR bearings were corroded and the propeller shaft was so worn I had to have a new one machined. No preventive maintenance entries found in the airframe logbook. Installed new belts and bearings all around.

We need to get a spring scale for Eddie to measure and post his thrust from his fire-breathing green machine.
 

N447MR

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eddie;n1135958 said:
That's right the belt and the end plates are turning at the same speed,I have never thought about track adjustment,I use goodyear belts however the name has been

changed to contitech hawk as continental tires bought the goodyear line of rubber products buts its still the same quality,My belt is 3 3/8" wide(85 mm),

and I paid $120 for the belt,I have never changed my bearings and have about 800hrs on them,I changed the belt at 400 hrs.My Subaru engine is producing

230 HP and I swing a 5 bladed 68" prop pitched to 14 degrees and so far the PSRU has been good.
yeah man, I'd absolutely love a ride in your machine. I can't imagine the time you've put into the seemingly very practical and necessary mods so many gyros could benefit from. Continental is who made the new belts I bought. Still have to get them on. I had heard that the bearings on the RAF models had some issues, but that was probably the first ones out and I'm sure things have changed. I'd love to find the time to figure out that turbo project, but time is scarce. Will probably have to settle for the Cam grind if I can get the time for that.
 

eddie

RAF, turbo subaru 230hp
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N447MR thank you,the mods have happened over a period of several years and I really enjoy working on the Gyro,where you live a turbo is probably not

needed I have never flown mine at a low elevation I imagine it would be awesome and way overpowered.
 

Kolibri

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I have never changed my bearings and have about 800hrs on them
You may be taking an increasing chance (with your crank pulley in particular), from what I've gleaned on the forum.
Those bearings are subject to considerable heat and belt tension. 800 hours is a lot.

Thrust data would be interesting; probably 700+ lbs.

Regards,
Kolibri
 
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