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topflite spitfire retracts

Old 10-12-2009, 05:03 AM
  #1  
GaryBarry
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Default topflite spitfire retracts

HI all

I have just purchased the topflite spitfire mk 9. I see that it requires modification of the retract hinge so that the cylinder is coming from the other side. Is this possible to do with mechanicals? I would prefer mechanicals due to the lower cost.

Thanks
Gareth
Old 10-12-2009, 09:54 AM
  #2  
JeffH
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Default RE: topflite spitfire retracts

mechanicals will be tough since the gear is mounted at an angle from each other. In other words, the push-pull rod will not be in line with each other so that the 180 degree servo will work properly. Also the since the center section of the wing is mostly scale, the wing has two dihedral breaks. The retract pushrods would have to bend upwards. Of course I guess you could use two retract servos, but this is now getting to the same price point as the pneumatics.
Old 10-12-2009, 11:23 AM
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SCALECRAFT
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Default RE: topflite spitfire retracts

Hi

Good question.

Yes it will work.

I have a 48" span 109 with mechanical retracts. Same problem and idea as the spit.

What worked for me is an old single S-8 Futaba servo, 180 degree sweep, (like todays strong retract servos) really slow movement and a combination of piano wire and goldenrod.

For gear up, the wire and cable are pulled, so not much of a concern about the cable. Support the cable as needed.

For down, once the "lock up" is released, the gear just drop from there own weight.

The dihedral problem, if any occur, can be corrected by your mounting blocks, and bending wire strut, plastic covered, if not a scale robo strut type.

I could post pics of my wing for reference if you want to try it.

Steve

Old 10-12-2009, 11:33 AM
  #4  
da Rock
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Default RE: topflite spitfire retracts

Keep in mind that the dihedral of the airplane and the fact the struts retract outward not inward, the amount of movement needs to be more than 90degrees.

Is that important?
Well, most gear sold for P51s, P47s and such (where the struts retract inward) often are advertised to move 80degrees. Check most retract mfg's and you'll see the good ones offer those 80degree ones. It was worthwhile to do for the P51s and such. It would be just as good to have the same for the Spit, it would seem.

Why is it important? other than looks, if they're not perpendicular on touchdown, the hinging will have to absorb a side impact it doesn't see when correctly angled. It'll see it every landing, and have to deal with it all the time the sucker is taxiing or just sitting. Most aren't designed to see side torques like that at all.
Old 10-12-2009, 06:54 PM
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bigtim
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Default RE: topflite spitfire retracts

here's the problem as I see it there is alot of stuff crammed in the wing near the landing gear, and center section, the flap bell cranks, and the flap servo is also in the center section, a rertact servo would fit in the forward area but it would be tight. the center section is strait and the wings angle off of it as well so its a bit tricky.

the gear have a slightly off center angle to them and rearward angle as well so working out the geometry for smooth action might be a bit of a challenge, it could be done of course but your not really saving that much money for the extra work and hassle since the wing is designed for air gear to be used.

the retracts from robart can be had for about 120$ U.S. for the TF spit, my wing at the retracts and my flight mech.
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Old 10-12-2009, 09:21 PM
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Default RE: topflite spitfire retracts

In the pic in post #5:

Note that the wing shown in post #5 has the retract in the outer panel having nothing to do with the inner panel dihedral. The three piece wing would be a concern only if the retract mount was in the center section.

Also note that the landing gear in the pic with the model on its gear are angled out a bit and not perpendicular to the ground . Leading one to think that a 90 degree sweep on the gear will work. As displayed by pic.

Steve
Old 10-13-2009, 12:19 AM
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Default RE: topflite spitfire retracts

Hi there-Big tim I saw some of your comments on Tubig's very helpful thread-good to see your finished plane! Mechanical retracts seem much cheaper and hassle free? I know they have their drawbacks but the lower cost is very appealling. As I understand it the spit's landing gear is 90 degrees, with forward rack when down and backwards rake when up. Surely as long as the retract servo is parallel to the line of action of the retract, it should work? My only issue is arranging modifyin the retract such that it is being operated from other side (due to outwards retracting)
Scalecraft I can see that you understand my dilema but I dont understand your solution! Surely the gear must lock on both up and down? I am wondering if it's possible to modify standard mechanical retract 'hinges' (sorry dunno what they are actually called) such that the servo is operating from the other side?
Thanks guys!!
Old 10-13-2009, 07:57 AM
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Default RE: topflite spitfire retracts

ORIGINAL: SCALECRAFT

In the pic in post #5:
Also note that the landing gear in the pic with the model on its gear are angled out a bit and not perpendicular to the ground . Leading one to think that a 90 degree sweep on the gear will work. As displayed by pic.

Steve
Got no idea if the gear on the model in the pic is 90 or 80 (gear designed for a P51), but it's certainly not perpendicular to the ground is it. Putting any gear in that doesn't take the dihedral into consideration is going to give one of two problems, one of which is shown by that pic.

Here's a pic of a fullscale Spit with it's gear down. It's obvious the sweep is greater than 90degrees. If the gear in the model is placed in the straight section of the wing, the part without dihedral, it really will need to sweep more than 90. Otherwise the wheels will be hanging out when they're up if they only sweep 90degrees. If the gear in the model is placed in the dihedraled part of the wing, and they're 90 degree gear, then when they're down, they'll be angled out a fair amount. Either way the gear is installed, the sweep has to take the dihedral into consideration.

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Old 10-13-2009, 08:53 AM
  #9  
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Default RE: topflite spitfire retracts

The instructions call for 90 degree retracts, mounted at such an angle that they move forward of the spar when down and aft when up. As far as I can see the dihedral takes care of the angle (the topflite undercarriage is much wider than scale). Will electric retracts from Lado not solve this whole problem? They seem really good value at $175?
Old 10-14-2009, 09:18 AM
  #10  
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Default RE: topflite spitfire retracts


ORIGINAL: da Rock

ORIGINAL: SCALECRAFT

In the pic in post #5:
Also note that the landing gear in the pic with the model on its gear are angled out a bit and not perpendicular to the ground . Leading one to think that a 90 degree sweep on the gear will work. As displayed by pic.

Steve
Got no idea if the gear on the model in the pic is 90 or 80 (gear designed for a P51), but it's certainly not perpendicular to the ground is it. Putting any gear in that doesn't take the dihedral into consideration is going to give one of two problems, one of which is shown by that pic.

Here's a pic of a fullscale Spit with it's gear down. It's obvious the sweep is greater than 90degrees. If the gear in the model is placed in the straight section of the wing, the part without dihedral, it really will need to sweep more than 90. Otherwise the wheels will be hanging out when they're up if they only sweep 90degrees. If the gear in the model is placed in the dihedraled part of the wing, and they're 90 degree gear, then when they're down, they'll be angled out a fair amount. Either way the gear is installed, the sweep has to take the dihedral into consideration.

Full scale yes. But not in the model. In this case, In the pic they are in the outer panel. The mechanical retracts such as the supra-ez can allow for some sweep adjustment with the allen bolt.


Steve
Old 10-14-2009, 11:31 AM
  #11  
da Rock
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Default RE: topflite spitfire retracts

ORIGINAL: GaryBarry

The instructions call for 90 degree retracts, mounted at such an angle that they move forward of the spar when down and aft when up. As far as I can see the dihedral takes care of the angle (the topflite undercarriage is much wider than scale). Will electric retracts from Lado not solve this whole problem? They seem really good value at $175?

One would certainly hope the instructions would be correct.

H9 Spits have the gear inline with the spar when up. LADOs most certainly do not bring the gear down far enough and they're mounted in the dihedralled section on the H9s.

Anybody got a picture of a TopFlite spit with the gear completely retracted and one from the front with the gear down? The TF mounting is with an aft sweep and it's angled in the wing. No matter what the angles, if the gear moves only 90degrees, it's going to be less than perpendicular to the ground or not into the wheelwells (or a little of both) by whatever the angle of dihedral is. And the LADOs don't go 90 like the TF Spit is designed for.

The youtube videos I've seen only give fleeting glances from front or back and darned it the struts look perpendicular. They only show retracted gear in flight, and even TF has only this:
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Old 10-14-2009, 11:57 AM
  #12  
da Rock
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Default RE: topflite spitfire retracts

Bottom line is, all 90degree retracts are going to place the struts the same depending on the model design. All will put the tires in the wheelwells or not, just the same. LADOs won't make your Spit look any different than any other 80degree gear will. But they aren't 90degree retracts. They stop 10degrees short of what TopFlite recommends.
Old 10-14-2009, 04:41 PM
  #13  
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Default RE: topflite spitfire retracts

da Rock

TF instructions call for 90degree due to the reason that the gear are in the outer panel.


I always look to adapt my existing retracts to any kit, plan, or arf that i have. Degrees do not enter the picture, just the finished function and look.

I use air at times like these when I just want the right extended leg position. Up doesn't matter, its air holding it. No binding servos.

Instructions are just a suggestion.


Steve
Old 10-14-2009, 05:52 PM
  #14  
da Rock
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Default RE: topflite spitfire retracts

ORIGINAL: SCALECRAFT

TF instructions call for 90degree due to the reason that the gear are in the outer panel.

EDIT: Save yourself some time and skip my dissertation here. Look at the picture in post #16 of this thread. It shows the gear as installed by the instructions.



Think about it.

The outer panel is not parallel to the ground. It is at an angle from the ground, whatever the dihedral angle is.

When the gear is up, the strut will be parallel to the wing (and in line with the dihedral) and neither the strut or wing is parallel to the ground.

When the gear is extended, it sweeps down 90 degrees. It'll stop perpendicular to the wing. I stops short by however much the dihedral angle is from being parallel to the ground. It won't be "straight up/down" at all.

If a wing has 5degrees of dihedral, a 90degree gear in that wing will stop 5degrees short of being perpendicular to the ground. An 80degree gear will stop 15degrees short.

The LADOs appear to not be 90 or 80degree gear. They appear to be designed for whatever either the TF or H9 P51s have for dihedral. Here's something that shows how far short they stop, short of a right angle, and why they aren't going to be adjusted to get the extra movement easily. That's steel and brass there. Excellent construction.
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Old 10-14-2009, 08:51 PM
  #15  
bigtim
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Default RE: topflite spitfire retracts

first there is a few differences betwen the TF and H-9 spit gear positioning

the TF has a angle and drop to the rails, which was a pain to get them perfect,I ended up using epoxy and micro balloons to "bed" the retracts so they would operate smoothly, the smallest twist in the plastic robarts caused binding problems after only a couple of cycles, as the pressure dropped, they now operate perfectly.

also when installing the struts, TF has you bend the strut at a slight angle for the forward rake needed to retract into the wing, this requires a eliptical opening for the wheel to fit into a resonably small hole in the wing unless you want a overlarge gash in the bottom of the wing.

LADO is coming out with a 90o retract that will work in the TF spit http://www.lado-tech.net/proddetail.php?prod=60-5 its not available yet, but putting a 85o gear in the spit won't work with there design, or your going to have a splayed out gear that is going to look super goofy, as it is there very lightly splayed out.

if you look at the photo the dihedral in the TF is no where near that of a H-9 warbird ARF, its actually a pretty flat wing.
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Old 10-14-2009, 10:09 PM
  #16  
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Default RE: topflite spitfire retracts

Ask and you shall receive! These pics are without the sheeting so you can reference the spar. This extra angle in the mounts will help to fight nose over when the gear is extended and it appears the H9 is designed close to the same way. Getting the axle in front of the spar and closer to the leading edge is an important part of minimizing the nose over tendancy along with other factors. The wider gear stance also helps on landings. Neither are anywhere close to scale anyway and that is obvious when looking at it from the front with the gear down. It is the compromise made with the design of these kits. My other limitation was making sure the air cylinders cleared the spar and wing joiners in the center section. It is a bit tight still in a 60 sized Spit, especially when squeezing the air tank/valve in the center section.

ORIGINAL: da Rock

Anybody got a picture of a TopFlite spit with the gear completely retracted and one from the front with the gear down?
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Old 10-15-2009, 05:42 AM
  #17  
da Rock
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Default RE: topflite spitfire retracts

Thanks rustypep.

In your picture it's obvious the struts splay a bit and are short of being perpendicular to the wing. A picture is worth a thousand words.

Here is a pic of my H9 after I the MODIFIED lado's. They weren't capable of being altered internally to get any more extension that I got, but they're a whole lot better than stock. The airplane has pretty decent ground handling while the landing impacts go straighter into the mechanical parts.

(FYI, the gear doors in the pic have been temporarily taped directly to the struts. That's definitely temporary as the gear won't close with them that close to the struts.)

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Old 10-15-2009, 06:05 AM
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Default RE: topflite spitfire retracts

BTW, from your pictures it appears that the TF setup also drops the wheels further aft than the H9 setup does. The TF certainly is significantly more scale for sure, but I'd bet the H9 wins at ground handling.

I don't have a picture directly from the side, but this very early pic does show the wheels to be decently forward. That's certainly not scale, but is a great benefit to ground handling for most models.

Jeez, don't you just love digital cameras.
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Old 10-15-2009, 08:16 PM
  #19  
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Default RE: topflite spitfire retracts


ORIGINAL: GaryBarry

HI all

I have just purchased the topflite spitfire mk 9. I see that it requires modification of the retract hinge so that the cylinder is coming from the other side. Is this possible to do with mechanicals? I would prefer mechanicals due to the lower cost.

Thanks
Gareth
Mechanicals can be operated from the other side without modification by turning the control horn of the retract pushrod to the side or top (depending on what's convenient) and then bending the pushrod from the retract servo to reach around to the retract's control horn. On the Spitfire, the servo pushrods of such a reversed, mechanical setup look to intersect forward of the wing spar at the center of the wing. That is possibly where the retract servo could be mounted if you make some small holes in the spar webbing for the push rods to pass through. If that won't work because of the wing dihedral angle, two retract servos can be used instead (I use a single HS-75 retract servo http://www3.towerhobbies.com/cgi-bin...ervo&search=Go in my H-9 Corsair and Corsairs have more wing bend issues than a Spitfire, so I'm guessing that a single servo will work on a Spit too). Looking at the pictures in rustypep's post, it appears that if two servos are used they could be mounted aft of the spar or maybe even side by side in front of the spar at the center of the wing where a single retract servo would be mounted. If you use two servos for the retracts, you'll only need servos with half the torque of the HS-75 (92oz/in). I've had good luck using standard servos (42oz/in) on my World Models Zero60. Also, the HS-75 costs about $30, while two standard servos cost roughly half of that. I did find a standard servo that has 47oz/in of torque but I've never tried these servos myself. http://www3.towerhobbies.com/cgi-bin...?&I=LXTJJ7&P=7 Hope this helps.
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Old 10-16-2009, 12:41 AM
  #20  
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Default RE: topflite spitfire retracts

da Rock...the splay looks much better after your mods to the H9. Nice job on that. That is the one part that I don't like about the TF. It looks like the H9 stance is also wider than scale (TF Spit is the same way) and that will help with the ground handling even with the splay reduced. A scale undercarriage is one thing that makes the Spit a bad first time warbird. That is something the P-47 doesn't have an issue with as a model. It still looks right!
Old 10-16-2009, 06:47 AM
  #21  
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Default RE: topflite spitfire retracts


ORIGINAL: rustypep

da Rock...the splay looks much better after your mods to the H9. Nice job on that. That is the one part that I don't like about the TF. It looks like the H9 stance is also wider than scale (TF Spit is the same way) and that will help with the ground handling even with the splay reduced. A scale undercarriage is one thing that makes the Spit a bad first time warbird. That is something the P-47 doesn't have an issue with as a model. It still looks right!

Yeah, the H9 is wider than scale, and nowhere close to having scale layout. They retract parallel to the span. Nothing like the fullscale.

The TF layout is really good scale-wise, but that's really can't be good for a model's ground handling. I was planning to do a TF until I saw all the pictures. Competition scale isn't what I enjoy flying..... or taxiing.
Old 10-19-2009, 07:57 AM
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Default RE: topflite spitfire retracts

The topflite spitfire retract outwards and are wider than scale. Does anyone know when the Lado 90 degree retracts will be in stock?

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