Yorkman Posted November 9, 2020 Share Posted November 9, 2020 I will need, if possible, a pair of 100 degree electric retracts, for a 6' span four engined transport which is in the design stage. 90 degree rotation not required! Not a clue as to what the projected weight is, but the lumpier the units the better. Are there any out there that could do this job? Cheers all. Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted November 9, 2020 Share Posted November 9, 2020 Hi E flite makes a 100-degree unit part no EFLG320 for 25-46 size engines, they also do 105 degrees and 95 degrees. I cannot see a 60 size in their range (Horizon Hobbies) Hope this is of some help, any clue as to the model your designing?? Regards Robert Quote Link to comment Share on other sites More sharing options...
Jon H Posted November 9, 2020 Share Posted November 9, 2020 check out electron retracts in spain. a customer told me he was very impressed with them Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 9, 2020 Author Share Posted November 9, 2020 Posted by Robert Parker on 09/11/2020 18:30:25: Hi E flite makes a 100-degree unit part no EFLG320 for 25-46 size engines, they also do 105 degrees and 95 degrees. I cannot see a 60 size in their range (Horizon Hobbies) Hope this is of some help, any clue as to the model your designing?? Regards Robert what does '25-46 size engines' mean? It is no help whatsoever! For a start it's a multi-engine model, and it will be electric! Why do they not say the maximum weight of the model (as some others do) Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 9, 2020 Author Share Posted November 9, 2020 As to which aircraft, it's a secret, as I can't see any others out there and hope it may be a first! Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted November 9, 2020 Share Posted November 9, 2020 For ref: Models in the engine range of 25 - 46 will weigh around 3 to 5 lb. . Retracts in this weight range tend to be a bit feeble. Electric retracts have a track record of being less robust than other types so it is better to go for heftier units if possible. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 9, 2020 Share Posted November 9, 2020 Do they retract backwards? Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 9, 2020 Author Share Posted November 9, 2020 Posted by Martin Harris on 09/11/2020 21:16:46: Do they retract backwards? yep Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 9, 2020 Share Posted November 9, 2020 Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted November 10, 2020 Share Posted November 10, 2020 As they don't need to twist and turn, there are a couple of options available. 1). Just take a normal retract and mount it (rotate it) 90 degrees so it retracts backwards. 2). If 100 degrees is required, it is possible to cheat by mounting a "normal" 90 degrees retract unit at an angle to rake it forward. Mount it high in the wing if it is necessary to hide the wheel. Or.... make an engine nacelle a bit deeper to accommodate the wheel. 3). It is possible to change the retract angle by elongating the slot in the sides of the retracts so the support pin can travel a bit further. Elongate it in the down position, not the up position, or it will crash into the retract unit and not lock. . . . It might be best to experiment with this on a basic, cheap-and-cheerful unit before attacking an expensive unit. Edited By Brian Cooper on 10/11/2020 02:27:39 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 10, 2020 Share Posted November 10, 2020 Give Justin at Rapid RC a call .He stocks electric retracts of all sizes and might have 100 deg sets . Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted November 10, 2020 Share Posted November 10, 2020 Hi, I'm not too sure why they used engine size for their sizing but I have used E flite retracts on both of my 4 engine electric models the being my Short Stirling and FW Condor and Tony Nijhuis own retracts for his Lancaster all 72" span (1.8m). All of the units have been OK but I have had trouble with bending the central pin 4mm wire. My MK I design Short Stirling MKII the spring helps absorb the loads, What I like the E Flite retracts is the all metal construction. Regards Robert Quote Link to comment Share on other sites More sharing options...
Nik Harrison Posted November 11, 2020 Share Posted November 11, 2020 I had a similar problem getting retracts for my build of the Brian Taylor Bf-110. It required 110 deg rotation to park the large wheels in the nacelle. I ended up making my own from Robart air cylinders with a little help from a friend who made the metal actuation block. Used Coral Draw to get the dimension correct and only used metal were it was essential. Worked a treat as air up/air down retracts. The only reason I can show these pictures is because I stalled the 110 last week on landing and destroyed the model. My own fault but it was 15 years old. Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 11, 2020 Author Share Posted November 11, 2020 That's a shame! The York has now been flying for 16 years (off and on!) and I hope many more years to come. I have decided that I will try and engineer some 'proper' undercarriages for this new project, with functioning drag braces, as per the York, but with a much simpler actuating and adjusting system. I really don't like just relying on the strength of the retract unit to hold the wheels against the landing forces. It works ok on my Mossie, but that's a proper lightweight. https://www.youtube.com/watch?v=dVdAE2CE2K8&ab_channel=MartinAbbott Quote Link to comment Share on other sites More sharing options...
Nik Harrison Posted November 11, 2020 Share Posted November 11, 2020 Not sure what you mean about "retract unit strength" as any retract setup must be able to survive such landing forces. The unit above "locked" in both up and down positions. If there was any weakness it was in the wire strut. The 110 was 11lbs and the wire legs were amenable to being straightened when required. Enjoyed your video though. Cheers. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted November 11, 2020 Share Posted November 11, 2020 Nik, the issue with using commercial retracts this way is that they are designed to take fore and aft landing forces at 90 degrees to the unit, when the forces are applied along the mechanism shock loads are applied to the actuating fork. This fork is usually the point of failure, I've heard of several Eflite units breaking off one arm of the fork just from the side loads of a cross wind landing. The same applies to the twist'n'turn retact units. As you say, the use of a coil in a wire leg is usually enough to take up the shock load. I bet an oleo leg wouldn't be as resilient. ps - I like your dummy oleo units! Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 12, 2020 Author Share Posted November 12, 2020 What Bob said Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted November 12, 2020 Share Posted November 12, 2020 Indeed. The problem with mounting the retract unit deep in the nacelle to accommodate the wheel is that it makes the leg longer, which makes it more prone to bend, and puts more stress on the retract unit. Quote Link to comment Share on other sites More sharing options...
Yorkman Posted November 12, 2020 Author Share Posted November 12, 2020 Posted by Trevor Crook on 12/11/2020 19:07:32: Indeed. The problem with mounting the retract unit deep in the nacelle to accommodate the wheel is that it makes the leg longer, which makes it more prone to bend, and puts more stress on the retract unit. exactly. it's a double whammy of stresses acting in line with the direction of movement and the added leverage due to needing to bury the diameter of the wheel rather than the thickness of it. Quote Link to comment Share on other sites More sharing options...
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