Jeffpro

My Feedback: (1)

I love wardbirds. But I'm discouraged by the fact that nobody seems to make retracts that are reliable. I recently installed a set of Robarts in my 1.50-size H9 P-51, but even they seem to be nothing but trouble. One of the retracts doesn't lock properly in the down position and is prone to folding up after landing. I've scraped up the bottom of my plane so many times and broken so many props that I'm tempted to start a company to make high-quality retracts and do it right. I've got this funny idea that people would pay a reasonable price for gear that really work.

Anyone have any experience with Likes electrical gear? Are they dependable? If I try them will I never want to fool with pneumatic retracts again? Are Spring Air retracts fundamentally better than Robarts (aside from the superior failsafe mechanism)? Does ANYBODY make retracts that will stand up to the occasional rough landing?

Richard L.

My Feedback: (24)

Robart air retracts are pretty good, especially the all-metal ones. Spring Air retracts are also good. You want to check out a set that are bored out for functional oleo struts, such as Robart #551RS and #631RS. Both of these are 85° retracts that have positive up and down locks and can take 7/16" or 1/2" diameter oleo struts. I believe Spring Air retracts can only take 3/8" diameter oleo struts.

For what it's worth, I've had good luck with Robart 615's rotating retracts, which tend to give people the most problem:

* [link=http://www.whitetyphoon.com/rc/vq_p40/movies/touch_and_go.wmv]Touch and Go[/link]
* [link=http://www.whitetyphoon.com/rc/vq_p40/movies/landing.wmv]Landing #1[/link]
* [link=http://www.whitetyphoon.com/rc/vq_p40/movies/landing_17.wmv]Landing #17[/link]
* [link=http://www.whitetyphoon.com/rc/vq_p40/movies/landing_18.wmv]Landing #18[/link]

josephair

it seem like all retract sux , if you look at all the post on rcu. make your own.

Peter_OZ

My Feedback: (1)

Richard,

my 615s in the P40 have been reasonable. In my Pica Spit I have Spring Air and the only problem has been the axle rotating about the strut at times causing the wheel to toe out at right angles to the correct direction. Acts as a great brake hehe

Robart retracts in the larger sizes appear to be very good.

Prob with electrical retracts such as worm drive etc is electrical noise from motors, RXs hate it. "Danger Will Robinson!!!"

cheers
Peter

WLJ

My Feedback: (108)

It's been my experience that proper installation makes or breaks the reliability of operation,especially with air units of any make. Something as simple as uneven pressure on the screws holding the units in the wing will sometimes cause binding.(Twist the Housing) I hardened the screw holes in the wood with thin CA on my Big H9-P-51. An unnoticed drop got on one of the pivot pins. Not enough to stop it from working, but made it very sluggish. Disassembled, cleaned with Acetone, problem gone. WLJ

furloughed ual

My Feedback: (31)

the robarts for the H-9 1.50 P-51 had an issue.....the "down-lock" slot seemed it was not machined deep enough to provide a solid lock in the down position.....2 guys at our field had this problem.....either increase the slot for the down-lock if you are mechanically inclined and good with tools or call Robart.....I guarantee it's not the first time they will have heard it....If I remember correctly, they repalced the gear for one of the guys who talked to them about it....I think they knew (and maybe even acknowledged...don't remember) they had a problem with this gear...FWIW.....

dragoonpvw

My Feedback: (7)

I have all the types you mentioned, Robart large scale rotating (2 sets) are fine when maintained and hold up pretty well. One spring air trike set , I am not sure I like the fact that the gear is down for transportation but they work ok. Likes which I just accquired in a second byron p-40 are very heavy due to the motors and batteries but work very well, no interference but I do have an isolator. They are very sloppy for their age and need rebuilding, worse than most others that I have seen but i do not know how well they have been taken care of. I have 2 sets of Century jets and they look and work well but neither have been used much, the ones on my 17 pound electric ME 262 were originally made without down locks which made landings a bit strange when pressure was low, they were added later by CJ but I still cant see why they would design without them, I wonder about other models in their range.Finally I have varied mechanical, they work great without exception when they are adjusted properly and have the right servos, I know many people throw them out of kits without looking at them because of what they hear on here and at the field. In fact my 17 pound world models GS mustang still has the original mechanical set on it and it stood up very well to a big bounce the other week and works great, another guy at the field has the same kit and has flown his for a year or so with a 3.2 in it and the stock mechanicals so there you go.
The biggest problem I see with retracts (especially mechanical) is poor installation, many guys just cant adjust them and blame it on the manufacturers. Failure to lock up or down and binding pneumatically or mechanicaly is most often the fault of the installer and structural failure is by far more likely due to bad landings than bad manufacture. This does not mean that some models or ranges do not have problems or are worse than others and there is always a possibility of a faulty set but not to the extent that you will hear.
Good Luck
Paul

Jeffpro

My Feedback: (1)

That's EXACTLY the problem I ran into--that the down-lock slots weren't machined deep enough (or perhaps that the little tip that locks the gear in the down position wore down after 15 or 20 landings). Either way, it's not what I expected when I paid big bucks for brand-name retracts. I'm calling Robart as soon as they open this morning. We'll see if Robart stands behind its products as well as Horizon Hobby stands behind Saito engines.

Jeffpro

My Feedback: (1)

BTW, if you want to see a fun video of my H9 P-51, check it out at http://www.wintellect.com/images/movies/stang.wmv

abufletcher

Retracts are one reason I'll be sticking with WWI A/C, thank you very much! Seriously, I might someday try a Stuka or other fixed gear WWII bird but from what I've read on RCU and seen out on the field retracts are a major source of trouble. No to mention doing all those rivets.....

Jeffpro

My Feedback: (1)

Yep, retracts have been the source of 90% of the problems I've had with my big bird. First it was the flimsy mechanical retracts that came with it, which weren't nearly sturdy enough for a 15-lb plane. (What was H9 thinking?) Then, once I installed pneumatic Robarts and sturdy RoboStruts, it was that the retract mounting blocks weren't sturdy enough. After I ripped open the wing and reinforced the mounting blocks, the gear began collapsing about every other landing (even the BEST landings) because they won't lock in the down position. And I see these same problems repeated over and over by other club members. The other fellow in my club who flies the H9 P-51 currently has it out of commission because--you guessed it--the retract mounting blocks cracked.

I've been in this hobby for less than two years, but I love it and will be doing it for a long time. I am simply amazed at the fatal design flaws in the larger ARFs (another example is the hinges on the wing struts of Great Planes' 81" J-3 Cub, which are virtually guaranteed to fail in flight) and at the general unreliability of retracts and other mechanical hardware. The manufacturers do 95% of it right, but the 5% that they do poorly overshadows everything else. No one seems to hold them accountable, either. I read all the flying magazines, and you rarely read anything but glowing reviews.

What I would love to know is do the manufacturers KNOW they're selling defective products and don't care as long as they get your money, or are they simply clueless about how their products fare once they're in the real world?

paladin

My Feedback: (9)

I’ve been flying War Birds for 20+ years and come up with a retract installation that will hold together to the point of the mechanism will fail before the retract rails in the plane will. So I have planes I’ve build that are 18, 15, 13 years old and never ripped out or failed to actuate. Then I bought ARF’s, thought it would be a good way to pick up a windy day flyer that still looked good. My first ARC was a Model Tech P-51 and the retract mounts never maid it off my work bench but it was uncovered so I could do that work without having to buy three roles of covering. With in the first ten flights I needed to replace the engine mounts and I still have that plane and it lead me to purchase others.

The next was a VQ Macchi 205, Both landing gear mounts ripped out by flight 25 and the plane had quickly self destructed to a point were I would not fly it any longer by flight 45.

Then came a Kyosho Me109 which actually has over seventy flights on it and still has the original LG mounts, but a new covering.

Then a buddy Got the H9 60 size P-51D we modified the LG mounts and it is still holding up fine somewhere around 50 flights, but He quickly replaced the factory LG with Rhom-Air.

Lastly I bought a GP stuka and found its LG (not retractable) to be very brittle. On a dead stick which did not make it back to the field on a flared landing into an alfalfa field (I’ve set dozens of planes down in without incident) the LG were pulled out of the wing and actually broke the main spar in the gulls in the process. I was amazed that non of the “structural� members of the wings were damaged. So I glassed the gulls and thought for a moment about glassing the center section but decided against it because of the tight fit between Fuse and wing would need to be reshaped and I just did not want to spend that much time on an ARF. 27 flights later the wing folded at the unglassed center section.

I’ve purchased one last ARF the KMP Hurri, It will most likely be my last one! Mainly because I’m tired of spending all that time fixing things.

As for retracts I’ve used them all! I prefer Rhom-Air (air up and down), Spring air (air up only), [email protected] (Lenny Sarbin), and Platt retracts. The Rhom’s and Platts are so prevalent that they can usually be picked up cheap at swap meets sometimes with some repair required but for a good pair of retracts its worth it. If you have either of these and they are not reliable write me and we’ll get them working.

Good Luck

Joe

JDHammer

My Feedback: (1)

I've finally found a good solution for the retract problem on our grass field- Land Gear UP. Get a Bearcat, P-47, Wildcat-something tough that can land on its fuselage and your troubles are over! My P-47 has over a dozen gear up landings now without damage-seriously, it works.

Warbirdz01

My Feedback: (1)

When you look @ most of the "Giant Scale" warbirds and what their original "Designed Weights " are and then look @ how heavy many are being flown.......I can see why there are some retract problems........many of the models flown are loaded up with scale goodies and their weights go up.......My TF giant P-51 weighs 30 lbs.....that airplane/Robart gear comb was not designed for that weight.......although the gear was pretty good as long as I made decent landings.......It didn't hold up well for side loads or hard landings........I was replacing parts.....I mostly fly "Ziroli", "Don Smith" planes and I've had very good success with the gear in all my planes.......provided I avoided hard/bad landings...using all Robart gear........Warbird "Heavy Metal" has flying characteristics no other planes have......and sometimes landing them in crosswinds and short runways.....take their toll........but overall.....any of the gear problems I've had ....mostly have been my own errors during approach/landing...........Bill.......

Jeffpro

My Feedback: (1)

I've had my share of non-perfect landings as well. But it seems as if ARFs with retracts are designed with the assumption that every landing will be perfect. Back in my engineering days (I'm a former mechanical design engineer who hasn't practiced engineering in years), I would have been fired for designing like that!

I talked to Robart just now and they were very helpful. They asked me to send the retracts back to them so they could take a look at the one that doesn't lock in the down position. Nice working with companies that take an interest in your problem and want to help out.

paladin

My Feedback: (9)

Jeffpro, I am a practicing (for the moment) design engineer and have been for 24 years and I am taken back by the lack of attention given this problem. First off the fact that the mounts do not hold up and second that they are all installed at the wrong angles. A little trig. while laying it down on paper (which I would be happy to do for FREE) in the beginning then chooseing the correct materials for the job and they could double their sales just because its an ARF that's built correctly. If I had done the job they are doing not only would I have been fired but the company would be out of buisness!

I have two pair of retracts I simply will not use in their pressent form because they use the pressure in the cyclinder and an inclined plane to hold the wheels down (deployed) on a giant scale. I've conversed with the company involved without any satisfactory solution. So I'll have new cams made here at a model shop that will provide locking in both the retracted and deployed position. What we need is a standard! Ask AMA to compile all the constructive complants and creat a standerd that can be verified then those ARF's that demonstrate they can pass the standard can be sold as meeting that standard. The buyer whould have some idea what he is getting! the manufacturers (who have never flown a model in their lives) would have something from the buyers that was not filtered by wholesalers or retailers.

I like dreamin' (great song dont you think)
Got to go

Joe

Jeffpro

My Feedback: (1)

Great thoughts!

I remember the most profound lesson I ever received as a young engineer right out of college. I was given the job of designing a steel shelf that went on an equipment cart. I used all the stress analysis stuff I learned in college to design a shelf that would hold at least twice the 20 pounds of equipment that was to be placed on it. My boss reviewed my design and said "this needs to be able to hold 200 pounds with stength to spare." I said "Why? It'll only have 20 pounds on it." My boss replied "Yes, but it's two and a half feet off the ground. Somebody will sit on it, and it needs to hold up to that or someone will get hurt." I guess ARF engineers never had the boss I did!

In the absence of standards, it would help if the magazines would do critical reviews. I used to do product reviews for PC Magazine, and the rule there was that you called out a product's weaknesses as well as its strengths and that you tested, tested, and tested some more. Our industry simply doesn't have a magazine that'll REALLY tell you whether an ARF is worth your money. It seems to me all the reviews follow a formula that ends with the author's giddy remarks about the first flight. I submit that it's not the first flight that counts, it's the hundredth one. By that time, you know what's right with the plane and what's not and can offer an objective review of its quality.

Warbirdz01

My Feedback: (1)

Gentlemen............One of the areas thats not mentioned is the "shock strut"....large aircraft .....100,000lbs +....use a combination of mount design , material strength of gear and the "shock" absorbing strut......I've seen my share of "horrible" landings .....and no damage other than flatspotted tires.......I've found that on "almost" all Robart gear installed in my warbirds.....the strut absorption rate was set too "weak"....anotherwords the strut would collapse too easily............allowing the strut to "bottom-out"......therefor transfering downforce energy to the wing mounts.........the idea of the strut is to absorb all landing energy.....and taking landing loads off the wing/ airframe itself.......Check all of your gear struts for energy aborption capability.....and if adjustments are needed you can use dowel material or bushings to shim -up between the spring and top of the strut.....which should help unload the mounts some.............and keep your gear intact.........even on those "not-so-good landings........Bill........

Peter_OZ

My Feedback: (1)

hey Richard, nice landings mate

by the way you have to put $20 accross the bar - taxing with flaps down!!
hehehe


JeffPro, can relate to your design story. When I was in college doing my electronics degree we were always told that if you calculate that a certain device such as a resistor will disapate say 5 watts of energy then you need to use at least a 10watt resitor in the actual circuit. Now I work in Project Managment within Airline/airport IT systems but still do the odd bit of design work - yup still over engineer things!!

cheers
Peter

paladin

My Feedback: (9)

Warbirdzo1, While putting a spacer between the spring and the top of the strut will tighten it up and make it harder to push in. One has to be carefull not to space past the compressed minimum length for the spring, that is the point where it's coils are all resting on the ajasent coil. If that happens the total travel on the strut is reduced and the spring which usually does not fit perfectly in the upper strut will begin to deform and the initial gain in strut strength will soon be lost.

Jeffpro, submitted reviews to all the major mag's with onest assesments of the product and the only one that even gave it a second glance was R/C Report. But in the end they to sacomed to don't upset the sponcers.

Joe

rc34074

My Feedback: (5)

spring air makes the best 40-60 size retracts. for 60 size planes use the 100 series designed for 3/16 wires, as 5/32 wires are the weak point. for offset wires i use the wires top flite makes for their 60 size mustang. these are hardened music wire and come already bent with the offset in them. makes it easy to install and use them . i am one of those less than perfect pilots and have found that spring air gear hold up to my occasional imperfect landing.

the 600 series plastic frame robart retracts are worthless, in my not so humble opinion. so are the hangar 9 mustang retracts, although they are better than the 600 series robarts. the 3/8 robart oleos are only rated up to 8 lb planes and they are marginal even there- the offset is made with tubing not wire, so the offset bends easily.

robart does have a good looking 500 series retract that is all metal and will take a 7/16 oleo strut. they are much heavier (weight wise) than the spring air gear so i haven't used them yet.

i have avoided corsairs so far as i don't see anyone out there with reliable rotating retracts.

for larger retracts the 400 series spring air retracts are also very good. i have them in my world models 80 inch mustang and they have done very well there.

the 600 series robarts seem to have a weakness in the cam that operates the gear, and they break with moderate side forces in cross wind landings. sierra has a good beef up aluminum copy of this plastic cam to replace the original cam/beef up the 622 series used in the the top flite 85 inch mustang. i plan to get these upgrades before i fly my top flite 85 inch mustang.

i have not used larger retracts than these as i am limiting my warbirds to a maximum of a 90 inch wingspan, so they are easier to transport.

ed

Richard L.

My Feedback: (24)

Thanks Peter. That is how it's done on a rough grass field with rotating retracts. The plane looks so cool with flaps down while taxing.

Landings #17 and #18 were done on the same grass field without flaps since there was a fairly strong head wind on that day.

As for spring rate, the springs inside RoboStruts can be removed and replaced with stiffer springs if needed.

rslstft

My Feedback: (10)

I have to agree with WLJ as far as careful installation. That NOT to say there are not problems with manufacturing or those who build them. I have an old Great Plane Ultra Sport .40 with GP mechanical retracts and after sorting out the linkages, I have only had 1(!) gear up landing in over 250 flights. The wire struts have had to be replaced lately since they have actually gotten soft from so many landings. My H-9 Mustang never used the mechanical retracts that came with it, but were replaced with Robarts with Robostruts and have never failed to work properly after 75 flights and trust me, a lot a not-so-perfect landings. While many feel that buying an ARF with retracts should be able to be just put together and work fine, it just simply isn't the case from any manufacturer. Parts always have to be adjusted and strengthened and sometimes substituted with better parts. I know this when I purchase an ARF and accept the fact, but that is just me and I'm sure many with disagree with me, but I can't leave anything just "stock" anyway.

Russ

Meschmidt

My Feedback: (15)

As far as reliability, air retracts with good struts are the way to go. Struts cushion the not so perfect landings. Avoid spinouts and nose overs if possible as the side loads tend to bend and weaken components. Use quality tubing and nylon ties on all hose connections to minimize leaks. Good strong mounting beams are mandatory and reinforcing is required on all arfs. Use small wood screws to hold in the retracts in case of very bad landings that will pull out to minimize damage to retracts or mounts. Use separate battery on mechanical retracts in case of binding that will cause drain on the reciever battery. Retracts ARE a pain but if you want to fly WW2 warbirds, they just don't look good in the air without them. I fel the same as you did but be gentler with them and they will be alright! The best retracts available in USA are from Sierra Precision Components. Very pricey but excellent quality! As far as stock mechanical retracts that come with these WW2 arfs, they are ok as long as you don't fly the plane! Paul

Warbirdz01

My Feedback: (1)

Joe....I failed to mention to ck for coil spring bottoming after adding shimming material to tighten up the spring........but ...if needed just cut the spring if required to allow for complete compression of the strut.........My Ziroli B-25 had the weakest springs and I had to make quite a few changes to get them where they would work properly....When I put on the first 8-10 flights....I had an engine that didn't want to behave and made several approaches/landings with one engine @ idle and the landings were just plain lousy/hard and the struts bottomed out putting several skin cracks between the fuse and nacelles......easy fix but could have been avoided.......unfortunately these struts don't act exactly like the bigger aircraft that have fluid dampening which allows strut to remain compressed....ours have a tendency to "recoil" ...sometimes allowing the aircraft to" hop" on occasion....but I'll take the "hop" over damage to the gear mounts or wing .......Bill......