I read Bruce's review of these servos with a little dissapointment I must say, nothing wrong with his review - just that I import a fair bit of Corona gear direct from the factory...
Looking at the pictures of the gear failure, I think that it is not so much an issue of poor quality control as such, more I think a generally poor design. A press fit of a gear shape into a round hole, will always fail in my books, the pressure on the gear teeth is too high and they eventually give, especially with a soft material. I am in discussions with the guys at the factory at the moment and have made some suggestions as to how to improve the gear design (I am a mechanical design engineer by trade). These reviews are always good value in my book, regardless of the outcome. A bad review means there is room for an improvement, however in the case of a servo like this, it also means that I would limit it to use on a foamie model that doesn't matter too much. Interestingly I have also sold one of these to a guy who was using it as the steering servo on a off road 1/8th scale model - haven't heard back from him that it has failed at all, so perhaps Bruce did get a bad batch. I will give the guy a call and check up with him to see.
I am using some of the smaller DS929MG servos in a high performance glider of mine at the moment, I am crossing my fingers that these also do not have the same issue, although I have sold quite a few and not had any complaints yet. These servos are the same phsical size as the famed HXT900 servo, and thankfully do not suffer from the same gear teeth breakage issues. The HXT's are electronically great, but their plastic casings are weak and the gears even more so. Great for a light use application, but for the sacrifice of a few grams and the knowledge that I am not going to be replacing a gear set or servo on a frequent basis, I would go for a metal gear equivalent. Corona also have some new servos on the way, in between the 929 and the 538 size, a "midi" size if you like, similar in size to Hitec's HS85 and the Bluebird BMS380, also Metal gear and digital. I will be trialling a pair of these in a slope glider of mine when they arrive. Keep an eye out for the DS339MG servos soon...
What are other peoples' experiences with these servos?
Roger