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Robart retracts for H9 P51-d

Old 01-28-2003, 05:11 AM
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DeadSticker
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Default Robart retracts for H9 P51-d

I just accuired this beautiful plane and I really don't trust the look of the stock gear. Plus I really like the scale look and the functionality of the robart robostruts. Any help I can get on this subject will be very mutch appreciated! Thanks.....

~DeadSticker~
Old 01-28-2003, 05:52 AM
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Default Robart retracts for H9 P51-d

I got a Nosen P-51 kit with Century Jet retracts in a trade. I bought the Robart tailwheel retract but it didnt work the way I wanted it to. I also bought a Century Jet tail wheel retract and it didnt work the way I wanted it to either. I used Robart parts to build my own tailwheel retract. Between the two brands, the Century seemed to be a bit heavier duty and also heavier but both are quality products. I dont have any experiance with Robart mains but judging from the quality if the tail gear I bought from them, they should be ok. James

p.s. Thats a 6" Tru-turn spinner, the only brand I will ever use on a large plane. J.
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Old 01-28-2003, 12:33 PM
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Default Robart retracts for H9 P51-d

take a look at spring air retracts www.retracts.com they are good retracts, pretty strong, and the 700 series will take robostruts directly into the retract without having to grind those doggone flats for the set screws robart uses. i hate grinding those set screws . they use one standard servo to operate these air retracts.

i put spring air retracts in my hangar 9 mustang because the stock retracts were weak. i also have them in my world gs miss america p51 and my pica fw190d9. they have been very reliable.
they seem to take at least 60psi to retract relialy- i usually put about 100 psi in the tank, which is good for at least 6-7 retracts.

ed
Old 01-29-2003, 04:32 AM
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Default Robart retracts for H9 P51-d

rc34074

Which SpringAir retracts did you use in your H9 P-51. I am building one as we speak. I too, do not like the mechanicals.
Could you send me some pix of your setup.

Thx,
PHilR
pjr@iname.com
Old 01-29-2003, 05:07 AM
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Default Robart retracts for H9 P51-d

i used the spring air 116 retracts in mine- but then i noticed the 700 series. the 700 series looke to be the same as the 116s except they are designed to take the robostruts without using those darn set screws. so doing it over again i would buy the 700 series. but the 116s are fine.

i also changed the angle of the gear in the wing so the axles are even with the wing leading edge when the planes is level. this required modifying the plastic wheel wells but that was not too hard. this makes it easier to taxi and land without having the plane nose over.

sorry no pics - some day i will get a digital camera but not yet.

ed
Old 01-29-2003, 11:27 AM
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Default Robart retracts for H9 P51-d

Ed:
Thx for the info. I will check them out. How did you modify the wheel wells. Seems like it would be difficult to remove them. Also, how did you tilt the retracts forward?
Great idea, by the way.

Thx again,
PhilR
Old 01-29-2003, 05:41 PM
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Steve Collins
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Default Robart retracts for H9 P51-d

I had one flight with the mechanical gear that comes with this plane. That was enough! I installed Robart 605s in mine but I used heavy wire struts. I took the plastic wheel well inserts out. With them removed I was able to use a larger wheel. I lined the opening with thin balsa sheet and fuelproofed with epoxy and then painted with a fuelproof paint.
Old 01-30-2003, 01:08 AM
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pjr99
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Default Robart retracts for H9 P51-d

Steve:

Sounds like another good idea. Can you post some pix or email them to me??
Thanks,
PHilR
Old 01-30-2003, 05:26 AM
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Default Robart retracts for H9 P51-d

Hey guys!!!!!!! Grinding a flat for the set screw and putting the set screw in with some med. CA is the only way to go!
I have seen several trainers with the wire landing gear lose a wheel in flight then get trashed trying to land on 1 wheel and 1 plow. Its a simple matter of grinding the brass coller off with a dremel tool when the coller needs to be removed, and a whole lot cheaper than another kit. I always use hardwood wing spars so my planes can take a rough landing, but the kits that use balsa wing spars just cant take a 30 m.p.h. cartwheel. and if its a arf.........mo money mo money mo money. I fly like a seasoned combat pilot but I land like a fledgling. ( I'm getting better though) So I know how to rebuild a plane. Also, the fences at both ends of the runway are way too close to my plane and seem to jump up and grab them right out of the sky. (I have witnesses) The club I was flying at in Brazoria Co. even put that orange safety net on the fences. (Just for me) That just made it eaiser for my plane to find them. I have never lost a wheel but I have twanged some barbed wire.

hehehe

Its all fun, I like to build just as much as I like to fly.
Old 03-03-2003, 12:17 AM
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Default H9 P-51 landing gear

Hey Guys!

I just got a set of Robart Oleo struts (#653L & R, 3.25" max wheel) and am thinking that I should send them back for a pair of #663L & Rs so I can use up to a 4" wheel. It looks like the wheel well can take a 3.5" wheel. I am planning on pulling the strut wire out of the stock retracts and putting in a 3/16" wire, 3/32" doesn't cut it!

Any body tried this??
Old 03-03-2003, 02:23 AM
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Default Robart retracts for H9 P51-d

Not me, but if the retract mechanism won't be too weakened by enlarging the hole for bigger wire, I'd say go for it. I have drilled out wheels for bigger axels.
You could call Robart and consult with them. Iv'e talked to them several times while trying to find a tail wheel retract for a Nosen P-51 and they are very helpful. I even had a custom air ram built for about the same price as a stock one. Tell them what kit, about what it is supposed to weigh....Their website also has a referal link that matches retracts to kits. www.robart.com I think.
James
Old 05-10-2003, 05:28 AM
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Basil Yousif
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Default Robart retracts for H9 P51-d

If someone wants to stay in perspective of spending money after buying the H9 P51D what retract replacment can they buy for the plane that are well priced say around $40-$70, that will take care of the weak stock retract problem.
The Spring air retracts are allmost the same price as the plane. Is the set that come with it so bad that there weakness is just a time bomb waiting to destroy the plane.
In the Model airplane review the writer said he just used light sullivan 3 1/2" wheels to solve the problem.
I have one of these H9 P51D's on order.
If the Robart Mechanical retracts are the answer what is the model number for the retracts.
Old 05-10-2003, 01:52 PM
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Default Robart retracts for H9 P51-d

To keep thing simple I would drop in a set of MK mechanical Retracts (1.20 size) . Gator R/C sellsthem and they are some of the finest mechanical retracts on the market. That way you won't have to do a lot of retro fitting of an air system.

Hope this helps!
Old 05-11-2003, 12:36 AM
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Default Robart retracts for H9 P51-d

the spring air 116 retracts set is about $120. they use a standard servo to operate the air valve. this gives you a similar setup to the original wire retracts that come with this plane.

you can make both types work- but its easier to get air retracts set up and working.

the 700 series is set up to accept the oleos directly which is much easier than the set screw/grinding hassle.

ed
Old 05-11-2003, 02:40 AM
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KJSmitty
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Default Robart retracts for H9 P51-d

Spring Air all the way!
Installed in my H9 P51 before it even flew. They will all but slip right in with little to no modifications, but removing the plastic wheel wells, angling the base/mount forward, and using 3.5 inch wheels is key. I built my own wells out of balsa etc. Installed the tank, servo, valve/tubing etc. all in/on the wing. The only thing to hook up is the retract servo and aileron servos when readying for flight. $120 shipped, I use my mini bike pump/100psi and it works great. First retracts I have ever used and or installed. Absolutely no complaints. By the time you buy a good low profile retract servo and 3/16 wire let alone new mechanicals your well over the cost of the pneumatics. If you would like I could bring the digital C home from work and email you some photos...

Good luck

Smitty
Old 05-11-2003, 04:13 PM
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Default Retracts in H9 P-51

KJSmitty,
I would like to see some pictures of your setup. I have had this plane over a Year and have had enough of this gear, and the nose overs. Please post some pic's or email to me direct.
Also who sells the Oleos for the spring air 700 ???
Thanks
Joe
Old 05-12-2003, 01:03 AM
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Default Robart retracts for H9 P51-d

robart sells oleos that will fit the spring air 700s- you will need to make sure their oleos are long enough but they probably are. also "likes line" makes a nice set of oleos- more scale than the robarts- they are machined from bar stock aluminum. they will cost a bit more than the robarts but look much better. you will need to make sure they know which plane the oleos are for.

it all depends on how much you will spend to get gear that make the plane easier to land and look closer to scale.

ed
Old 05-12-2003, 05:12 PM
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3drc tim
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Default Keep the existing retracts

There have been a lot of good threads already written on this subject. Check the RCU search engine under H9 P 51.

Here's what I have done on my bird and the existing retracts. My plane has been flying for two seasons (lots of flights) with these changes and has had zero failures.

Tim

(from earlier thread)
For my H9 P-51, from the suggestions given on RCU, I first removed the gear (remember to tie something onto the acutating
wire between the gear and the servo because you will have difficulty getting the wire back in) and drilled them out in the drill press to accept larger wire gear legs (5/32 dia. wire if I remember correctly.) Larger wire helps with the bending of the gear and the "swaying" problem.

Then silver solder on CG wheel shafts to the new wires and grind a flat on the top of the legs to keep the legs aligned. Use a bit of toe-in here.

Use small pieces to metal tape to shim out any additional movement when the gear is down. Mount the tape to the plastic part of the LG that retracts with the legs. The tape will go insice the gear and by shimming reduce any futher swaying.

Addtionally, use slightly smaller and lighter foam wheels to take the stress off the retract servo. I replaced the H9 wheels with 2-3/4 inch foam wheels with diamond treads.

Finally, ramp up the rear of the LG mount by approximately 1/8 thick X 1/4 X 1-1/2 inch piece of plywood. Mount it right under the rear of each mount and you will all but eliminate the nose over problems. This changes the angle of the gear and moves the centerline of the wheels closer to the leading edge of the wing. This really makes a difference.

My H9 Mustand is flown off pavement and rough grass. Since these changes have been made to the bird it does not nose over or experience gear bending. Before these changes, I could set it on the bench and it would sway from side to side on its stock gear. It would nose over and bend the gear unless I was really careful on the landings.

Good Luck, these changes are working well for me. I hope this helps your birds as well.

Tim Adams

Also, you may have to "lower" your retract servo to acheive smooth operation and non acutating wire rub on the ribs between the servo and the gear.
Old 05-15-2003, 06:22 AM
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Default Robart retracts for H9 P51-d

With these modifications the plane doesn't even need the high priced retracts. I just got my H9 P51 and it looks like they might
have made some of these changes on these newer ARF's. The landing gear (gear thickness) looks okey - of course I don't know what the old ones looked like. Also they look like they have the landing gear angled forward to prevent nose over. The wheels look like there the heavy 3 1/2" wheels everyone's complaining
about but it's good to have these nicer looking wheels for show and fly with the (purchased separately) foam 2 1/2" wheels. if someone wants to help me check to see if this plane has had some of the retro done at the factory or are these just the same retracts that would benefit from the upgrades. I have attached some pictures of the retract system.
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Old 05-15-2003, 04:09 PM
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Basil Yousif
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Default Robart retracts for H9 P51-d

Here's another picture of the retracts.
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Old 05-15-2003, 08:19 PM
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Holeshot
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Default Robart retracts for H9 P51-d

Looks to me like the same retracts but they have been moved closer to the leading edge...........Dave
Old 05-15-2003, 10:38 PM
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KJSmitty
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Default Robart retracts for H9 P51-d

It looks like the same gear but without measuring it one can't tell. They may have used different wires etc that are better who knows. My stock wheels were 3 inches. I now run 3.5 inch tires on the spring airs due to our grass field, helps the roll factor... Big thing is many people may not have any issues with the stock gear. I made the change due to the numerous folks that did complain, the need for an expensive mech retract servo, and the fact that another guy in my club has a hanger9 pattern AC that has the same gear and they bend every landing/takeoff. Another guy actually fabricated his gear into a "fixed" position due to all the bending. Anyway its a small issue on a great plane. If I could figure out how to post a picture I would..... The wife actually gave me a new digital camera, early Fathers-day gift. Now I just need to figure out how to get the pictures from my hard-drive to this forum...??
Old 03-28-2004, 05:32 PM
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Default RE: Robart retracts for H9 P51-d

Just acquired a new 60 size P51. Measured the wire gear at 5/32" diameter. Front edge of gear mechanism is .9 to .95 " back from wing leading edge (it's tapered). Hard to tell, but axle seems to be about in line with leading edge. The wheels measure 3.25" OD. That may be a size larger too.

Does this represent an improvement over the original design?
Old 04-02-2004, 01:04 PM
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Default RE: Robart retracts for H9 P51-d

The one that I had purchased back then the landing gear were too wably. I had put in the spring air retract system with robart robostruts. The only thing to note with this setup is that you have to be very good at smooth landings because the more rigid the
retract system is the mpore load there is on wings when you land. It's better to start out with the wably retracts at the beginning so that by the time you become really good at landing the plane you can switch to the air system with the robostruts. This plane is much easier to land than my other P51 which is a world models .46 size. That one comes in pretty hot. The air system is way better than the mechanical system there's no comparison. You go through expensive retract servo's with the mechanical system. The hydrolic air system will last alot longer than mechanics and servo system. Spring air's are one of the best because if the system looses presure the gear automaticaly default to the gear down position instead of staying up in the wing. When you think of all the trouble you'll have with the mechanical system it's not that expensive to go with the air.

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