Wether you are planning to install just mains or trike retracts on scale model until now you didn't have much choice. Some models usually in the 60 size or below would have mechanical retracts these being operated by rods connected to a single servo. Pretty reliable if set up properly but in the event of a jam the servo would drag down your receiver battery and most likely cause a "brown out" or worse. Unless you didn't have a weight problem and added a battery just for the retracts.
Then we look at Air Retracts, some are air up/spring down (good as a fail safe) or air up/air down. Robart springs to mind immediately with the latter but what an eye wateringly price. Forget buying the parts separately, with 60 -120 size struts at around £58 each, then axles, air tank, air lines, operating valve. Flightline do some decent air retracts but hard to come by, no-one ever seems to have any in stock.
Now at last as promised E-Flite, a well known brand in electric models and power systems has come up with a good alternative - yes, electric retracts. Kits for the small jet 15 size to 120 size models.
You can choose between a pair of mains or a complete tricycle set. This review will concentrate on the EFLG430 60 -120 size trike set although most of the ancillary parts are standard over the range. The triike set comes with chrome spring wire, 5mm for mains and 4mm for nose leg. The mains legs are locked by two each 3mm grub screws. The nose leg is pre-assembled with the steering arm integrated which is lightly sprung loaded to return to centre.
The retract units are well made using aluminum for the housing and the retract hub. A powerful motor spins a worm gear to operate the mechanism. A brass pin sliding in a guide securely locks the retract in the up or down position. Now here comes the best bit, an integrated pcb board monitors the retract and if comes up against resistance, instead of pulling the battery power down due to overload, it simply returns back to it's original position.
The units are very light considering and the kits come with chromed axles, collets and the allen keys for the grub screws. Plus you get a y-lead or triple servo lead depending on your kit. The pre-drilled 4mm holes in the 60 -120 kit are near on the same dimensions as other retracts including Robart. In my case to allow for precise alignment I drilled these locating holes out to 5mm. Theoretically, if you have had air retracts previously then it should not be much trouble converting to these electric versions. Goodbye air-leaks and air pumps!
In a scale model no more slam up - slam down gear! These units take about 2.5 secs to operate over their cycle varying slightly depending on voltage - 4.8volts - 6 volts. The difference is only about 0.2 secs!
The mains are easy to modify to take Robo struts or similar. Just take out the 5mm wire and drill out to your strut size, max I would recommend to be 3/8ths (9.5mm) I drilled out mine to 5/16ths inch to 5/8ths in depth which allows both grub screws to locked into the strut. The steering/nose leg is a different kettle of fish though - I didn't modify this one as I could suffer with wire nose leg on my model. However, removing the 4mm leg would entail stripping the leg and steering arm right down, then drilling out for your strut and modifiying the steering system also. Not too difficult a task but a little time and patience consuming!
Pictured below are images of eflite retracts fitted into one of my B25 nacelles, the units being drilled out to take sprung struts
Overall, I think E-Flite has a winner here with the quality and price. A trike set 60 -120 size as I have used retails for around £150 (Robart = £399.00!) This set is good for models weighing in at 8 -15 lbs (3.63 - 6.80 kg)
I am so impressed so far that I am going to convert my 60 size ME109 and Spitfire to these very shortly - I had enough of chasing air leaks!