Is it possible to modify E-flite electric retracts

[Ben B]

I'm building a plane based upon a Cambrian funfighter Hurricaine. I'm intending to fit retracts to it but the problem is that the Hurricaine legs go inwards so I really need a 95 degree retract and E-flite only make 85 or 90 degrees. Is it possible to modify the range of movements for these retracts? I'm assuming they have a simple mechanical end-stop which could be "adjusted". I've tried looking on the internet for some close ups of the mechanism but can't find any which give enough detail.

thanks for any information!

Edited By Ben B on 31/08/2011 11:20:45

[Danny Fenton]

Hi Ben, not wishing to put a damper on your exercise, but the fun fighter is quite small and quite quick, I am not sure it would take the extra weight too kindly.

 

Unless you are of course modifying the model to be much lighter?

 

It will be interesting to see if the units are indeed adjustable as regards the end stops

 

Good luck with the project

 

Cheers

Danny

[Ben B]

Yes, the speed and size is a worry especially as Hurricanes didn't take part in D-day so there are no invasion stripe patterns even- a small, fast camoflaged model. Yikes

I'm planning on looking at the model to see if lightening it is possible. I'm putting an ASP32 in it so power shouldn't be an issue but the higher landing speed might be an issue particularly with retracts!

 

I've bought a Spit and a Hurricaine so I might just fly the Hurricaine without an U/C and then fit retracts to the Spitty.

 

[Brian Lambert]

Do you need 95 degree? surely if the wing has 5 degrees of dihedral and the wheels retract towards the centre of the wing and are vertical when lowered then 85 degrees is what you need.

[Brian Lambert]

There is a prototype for everything

[Frank Skilbeck]

Yep, E Filtes own Hurricane uses the 90 deg retracts, very good they are too but they aren't adjustable for retract angle.

 

As they are fitted to E Filtes Habu jet I don't think your Funfighter would be too heavy or fast.

[Martin Harris - Moderator]

Posted by Brian Lambert on 31/08/2011 21:39:51:
There is a prototype for everything

Seems there were 3 Hurricanes at least but I believe only one had the wing stripes - the others only had the fuselage ones. They belonged to No1697 Flight Air Despatch Letter Service (ADLS)

 

I wouldn't mind being a postie if I could have one of these instead of a bike!

[Danny Fenton]

I have to disagree Frank. The Funfighter I built many years ago was not designed to end up like a lightweight modern design. Liteply fus with blocks of wood requiring carving. Foam cored, obeechi veneered wings. Mine had an OS20 in it and it went like stink

 

 

It is seen here in the early 80's, no wheels just propped up on something for the photograph lol

 

The Hurricane retracts if I remember correctly, need to travel through slightly more than 90 degrees, but 90 will work (just about). The oleos/legs when lowered, are perpendicular to the centre section, not the outer panels which have the dihedral. If the wheels retracted paralell to the leading edge 90 degrees would work fine. But the wheels do not, they sweep back during retraction. Therefore you need a few degrees more to ensure the legs dissapear completely beneath the wing skin. I have a number of 93 degrees in my head. But am not certain.

Yep I am with you Martin let me have one of those and I would join the postal service

 

Cheers

Danny

[Ben B]

I think the reason they are supposed to be 95 degree retracts is because the hurricaine legs folded towards the fuselage not (as is more traditional) away. Yes, I spotted the ADLS one, I think it might be the colour scheme to go for!!! It also has a nice band of yellow all along the leading edge which will be useful.....

What nice dilemas to have. Better get the building board out and cleaned in preparation!

[Danny Fenton]

Ben I think your funfighter version may have wings made up of just two wing panels, not sure but I expect so. The full size has wings made up of three sections, the centre section is flat and has the undercarriage. The dihedral is in the join with the outer panels. In all my information I was referring to the full size angles.

 

 

So if your model has dihedral and that dihedral is generated at the centre wing join of just two panels, then yes you will need 90 degrees minus the dihedral. Or use 90 degree units and let the wheels move closer to the inner top wing skin.

 

Hope this helps

 

Cheers

Danny

[Ben B]

Oh yes! you would have thought the number of times I've read BoB books I would have noticed the three section wing! I did wonder about the 90s and having them at an angle, I'll have to see how deep the wing section is to see if I can have them as you describe.

[Frank Skilbeck]

Posted by Danny Fenton on 31/08/2011 23:09:14:

I have to disagree Frank. The Funfighter I built many years ago was not designed to end up like a lightweight modern design. Liteply fus with blocks of wood requiring carving. Foam cored, obeechi veneered wings. Mine had an OS20 in it and it went like stink

 

Danny I wasn't referring to the foamy Habu but the one with a glass fus and 6s power pack, these really zip along. Also E Flite do the retracts in different sizes for different weights of plane. BTW my mates funfighter spit had an OS 25 FSR in it and it went quite well.................................................................

[Danny Fenton]

Hi Ben, sorry I am a bit OTT when it comes to the Hurricane, bit of a favorite of mine. I am sorry I have drug your post off track too. The question was can you alter the travel of the units.

 

I dropped Chris Bott a message as he bought a set of the 120 sized ones at the Nats, and he says the up and down lock is mechanical and doesn't look as though it can be altered. He did send me a link to a guy that is letting them stall when retracted, not sure I approve of this method of reducing the travel. He cannot see a way of increasing travel. But what do I know

Frank, sorry mate, I wasn't implying for a minute that the retracts wouldn't be up to the job, I am just thinking that unless the surface was tarmac I wouldn't like to land a high wing loading, tail dragging warbird with tiny wheels. Add to that Ben is talking about fitting a 32 engine.

Cheers

Danny

[Ben B]

No a problem Danny Always good to talk warbirds. It was an obsession with Spits and Hurricanes that got me into r/c planes in the first place. It's just taken me a while to get round to building one... The e-flite ones stop moving when stalled and I do wonder whether this is how they detect the end-stops. I might get some anyway (I can always put them on the Spit when I build it) and have a play. Monitoring the ampage on a 'scope when stopped by a stall and when reaching the end-stops will quickly tell me whether they're doing what I think they are! If they are then reducing the throw is nice and easy, perhaps not so increasing it.

 

Good point re the small wheels. Our patch is mown quite infrequently so they might be a problem. I'm rapidly coming round to the "put them on the spit" option! I'm a slow builder as it is, over-complicating things might mean the thing never got finished! I'm tempted to put a rudder on the plane though....

 

As an aside (whilst talking retracts) wouldn't the pintle angle give toe-in? Is it better to have toe-in, toe-out or neither with retracts. I have vague memories of the BF109 being tricky to land due to toe-out and a narrow undercarriage so I'm thinking maybe toe-in is good?

[Danny Fenton]

Hi Ben, yep I could talk warbirds all day too

You will have to mount the wheels inline with the direction of travel when lowered, but because of the pintle angle they will not lie flat in the wing and the door also will not be inline. I have spent weeks trying to sort this very problem out on a YT Hurricane, including hinged doors etc. The best way to do it is by using that Pintle diagram I showed further up the thread. Basically it means mounting the retracts at a very specific angle, in all three planes, x,y and z as per the diagram.

When the pintle angle is right then the doors wheels etc are all correct.

 

There was an article somewhere i will try and find it about the lowdown on toe-in and toe out etc and the pros and cons for modelling. I remember seeing it but not having time to read it. You have jogged my memory, so many forums to keep up to date on I struggle sometimes.

Chris was saying that there was a sort of W section that formed the up and down lock. maybe we can get him to take a pic? They stop after 4 secs of being stalled thats for sure.

I will see if I can find that article on tracking.....

The 109 is just plain awful on the ground, very narrow track.......

Cheers

Danny

 

Just found the article written by PDR over on (whisper) RCMF U/C toe-in toe out debate

Edited By Danny Fenton on 01/09/2011 16:20:26

Edited By Danny Fenton on 01/09/2011 16:20:39

[Danny Fenton]

Excellent article and very eloquently explained, thanks Ben for urging me to find it again and this time read it

Cheers

Danny

[Danny Fenton]

Back to your original question:

 

Chris has sent me these....

 

 

Does that help?

Cheers

Danny

[onetenor]

chas a gearn the full size by the linkage geometry, /Strut

If I recall correctly the rake angles on the full size are controlled by the gearing and the linkage struts. Some tears ago there were retracts which had a twisting action on retraction which allowed the wheels to sit in the wells correctly. I am not sure how much rotation could be achieved. They may have been de Bolt retracts but not sure They would be rather heavy I think for this size model though.

[Martin McIntosh]

Danny, sorry to re open this old wound but this pic. taken over the Spitfire `bible` drawing shows the retract angle as 96 degrees, not 85. This is what I always understood to be correct. A bit critical at the moment on my rebuild which if I may I shall continue on your original thread.

[Danny Fenton]

Hi Martin, not sure if I understand your question?

[Martin McIntosh]

It seemed to me that you said 85 degrees for a Spit. which cannot be correct since even 90 degrees is not enough to compensate for the dihedral, but please correct me if I am wrong.

[Danny Fenton]

The retract unit angles back, and is not paralell to the skin. If you are unsure, make a mockup, its fairly easy to prove
If you dont wotk out the rake and pintle angles the wheel will not sit flush in the wing. The drawing at the top of the page was sent me by mr Goodger of Unitracts, and the numbers were for Micks and Brians designs. They should know. To be honest I cannot recall the angle, but have a set of spit retracts i could measure?

[Martin McIntosh]

The 90 degree ones on my original model sit outwards despite being fitted as per plan and just look wrong because of the central single dihedral. On the new one they will essentially be in the same place and at the same angle to the ribs in order to get them in height wise ( 2mm to spare only). They have an angle of 96 degrees built in since they were sold for Spits. Problems, problems.