JR have there new 591 servo out which is rated at I think 5kg and priced at about £12.00 ( about $17.00) I spoke to the guy at the UK importers the other day and he told me they have had very few returned as faulty,infact according to him they have a scimilar number of these returned as the digitals per amount sold.
I know most people encluding myself normaly use premium quality sevos that cost a small fortune in our jets but is there any reason why I should not use these servos on the ailerons and rudder on my turbine maverick? Doing this will save me over £200.00 ($300.00) on these three servos alone.

jason

When you are spending thousands on a jet it is very poor economy in my opinion to try and save a few bucks on servos. Always use the very best servos and batteries available. Wouldn't it be embarassing to build a five thousand dollar jet and lose it because you wanted to save 300 dollars on servos? Remember, reliability and durability are the single most important factor in this hobby. An RC jet is of absolutely no use to you and certainly no fun if it is grounded or crashes due to equipment failure or malfunction. In addition to my HotSpot (equipped with JR 8411's and Volz servos) I also fly a 200+ mph Jett FIRE 50 powered Diamond Dust. It is worth less than 500 dollars but I use 75 dollar JR 8101's on the elevons. I had cheaper FMA coreless servos on it but the bearings quickly failed due to the extreme loads, and it only has a 34" wingspan! When it comes to servos for extreme performance RC aircraft cheaper is definitely not better!

Dustflyer,

I have already stated in my thread that the importers have no more of these returned per amount sold than the more expensive ones so RELIABILITY IS NOT THE ISSUE although I do agree with what you say about the bearings but im sure if this one is not ballraced there is a ballraced version available for a few dollars more.
I do think that sometimes us jet modelers think that we must use the most expensive of everything regardless, maybe it come from the time when we had to because everything less than expensive was not up to standard. Like servos for instance, only a few years ago to get 5kg torque you needed to spend a fair bit of money but now you can get one with good relability for only a few dollars.

jason

I agree with the reliability statement you have made.

One thing you need to think about is deadband. If you are going to fly faster than most planes, then flutter becomes a concern. A surface using servos with lower deadband (all other things being equal) will have less likelihood to flutter.

The ball bearing support will also prevent the build up of slop that can lead to flutter as well.

Some of the better servos have better gear trains as well.

Overall I think your statement is good though, we should not spend money for moneys sake

Matt

If you mention its for a turbine add a few ££££$$$$$$$$$.
The servo prices jump up considerable amounts....

Jason, you wonna see the size of the inboard servos on the Mirage. They are the Futaba 3302 servos they are massive but have got metal gears and are 8kg. They were about £40.
The outter servos on the Mirage are the Voltz 5.5kg. Not cheap.


The Kentish Southern bunch

Jason,

No matter what advice you get its still what you think is best for your pocketbook. Back in `95 I built a sport F-15 with a turbine in it. I used all standard Airtronics servos and placed 80 flights on this jet before moving on to something else. If you keep the speed down to a reasonable level the standard servos would work fine, for a few bucks more get the BB type. I now typically spend lots on the JR 8411`s but have used Hitec MG servos in the past with good performance. I was thinking of not using the 8411 digi`s on the next project and going back to the JR 2721 servos.

Vin...

Years ago, Eddie gave me the original Isobar to fly (he had pretty much worn it out and was moving on). I refurbed it and put my RAM 750F in it. I was horrified to see that he had been flying it for years with dopey old Futaba 148s (non ball bearing crappo servos) on ailerons. As Eddie epoxies all of his servos in, I decided I would take a chance and try flying it as is. I flew it that way for many many flights and then I got one of the first RAM 1000s. This was before they made the changes to improve bearing life and detune the engine. It had, by far, the most power of any engine I have flown. It was balls to the wall in every way. That first flight, on the first full throttle pass, the canopy blew off cause the foam and fiberglass failed where the hatch latch was. That's how much power it had. I continued to fly that for a long time with those dopey 148s on ailerons. I am not saying that we should ignore thet lates greatest digital servos (all of my Multiplex digitals are performing perfect), but there is a definite tendency in the jet community to use the most expensive regardless of whether it is warranted or not. Its just a "mine's better than yours" playground sort of thing.

I think using 148s in a jet is pressing economy a little far, but I agree that just because we fly jets is no reason to mortgage the house to buy servos. I tend to use Futaba 9202s for most of the control surfaces on my jets. They are not cheap, but still much less expensive that the digital jobs. And they work just fine.

I have spoke to the importers of the 591 servo and found out they have 5kg torque a small dead band and are ballraced.
All for only £14.00 ($17.00) at my local shop.
So im fitting them in my Maverick and saving myself a small fortune.

jason

How much is that in inch-pounds of torque?

Woketman,

don't you know the conversion from kilograms to inch-pounds???

Well actually, I do not know by heart, but even if I did, it would be non-existent. At least in the R/C Universe that I live in (four dimensional, you see). Kilograms are normally a measure of force or mass, inch-pounds is a measure of torque (distance x force). So we are talking apples & Klingons here. I suspect the guy meant kilo-cm or something like that, but you absolutely CAN NOT express servo torque in kilograms, at least not and expect it to have meaning (in our universe, R/C or nor). ;-)

Over here in the UK they quote KG to CM but over there they quote OZ to Inch .
Im not 100%sure how it converts but the futaba 9450 I know as having 8 KG and you will know it as having 111OZ, so, as a rough guide the JR 951 5kg servo has 65/70oz. The futaba 9202 which most jet modelers have maybe owned at sometime gives 69.5oz so Im well impresed with these JR ones and im sticking three in the maverick to try them out.

jason

^5 to 70 oz-in for a Maverick sounds great to me. They'll do fine!

According to this 5kg - cm equals 69.45 oz - in

http://www.wihatools.com/conversions_torque.htm

I recall when servoes were all dicrete components, really crappy wipers in the pot that required cleaning often.
We got spoiled somewhere along the way, a mentality of "in for a penny - in for a pound" became rationalization.

"The greatest bar to furthering knowledge, to limiting oneself and ensuring permanent ignorance is contempt prior to investigation". Herbert Spencer.