I'm new to RC Helis, having played with one of those goofy Airhogs for several weeks and then playing briefly with a CX heli.

I just got the new Blade 400 and after going through the "pre-flight" check of control movement, I spooled it up on the carpet. After about 3/4 stick (with zero movement on the right stick), the heli rolled right over onto it's side instead of going up.

The rotors struck the carpet and pivoted in the blade grips, and it looks like one of the servos got the gears stripped off a few teeth. I zeroed the collective immediately and thought it didn't do any damage, but I can see why so many people have to replace servos now...

I've done lots of reading, and see this is going to happen a lot in the beginning... but I'll have to figure out why it rolled instead of went up like it should. But first I need to replace the servo or the gears. I'm no stranger to gears (mechanical and electrical engineering background), so I took the servo apart. It's only one gear with a few missing teeth, but it's obviously causing the servo to malfunction.

I'm going to head to my LHS today, but I called and they're pretty swamped and couldn't come to the phone. I was hoping to gather up a little information before I went. The book calls out a DS75H servo. The guy at the LHS wasn't familiar with it, but said he had a DS75 (no H) servo. He also said they have other servos (Hitech, Futuba) that would probably work. Since they're about an hour away (closest good RC store), I want to make sure I've got some part numbers and/or understand what I need to replace the servo.

Can I assume in most cases that the servo itself doesn't get burned up, so much as the gears get ripped apart? It would be super easy to just replace all the gears if they have those for sale... But if they don't, and all they sell are servos, what's the difference between the DS75 and the DS75H servos? And is anyone aware of a replacement of the DS75H that uses the exact same measurements. As it was, the DS75H was a tight fit in its mounting position. If it's not exactly the same, a replacement wouldn't fit.

And lastly, how does one go about re-setting the position of the linkage to the heli? I'm hoping it's a simple matter of plugging it in, screwing the linkage bar back on, and the resolver/encoder built into the servo will read the current position and set itself accordingly to the transmitter's stick position?

EDIT: I realize after thinking about it, that my assumption is wrong. Since the linkage arm coming off the servo isn't keyed (that I know of), how do I know what position to screw the arm back onto the new servo?

Torquestar--

Be careful on the carpet...A common occurance would be that the carpet will cause a tip-over from the carpet catching the skids. I would get a set of training gear, just for the first few start-ups to make sure everything is good to go on the heli. It will provide a safety net for initial start-ups/landings. I did the same for my Trex on my very first start-up. The 2nd attempt they were off, as everything was running smoothly. Congrats on your 'new toy'...Lol..I'am sure it will provide you with hours of excitement. remember, crashing is a part of learning...

I'am not familiar with the servo's that came with the 400. I do have the S75's in my CPP, and they've never had a problem in the 8 months that I've flown and crashed it. But I also hear there not the best bag of chips, so to speak...The nylon gears will strip out easily yes. But there are a lot of good servo's out there that will perform better and some even having metal gears for better strength. You can get replacement gears, like you stated that you might do, and taking the servo apart and installing one is an easy process. You just might want to do that for now, to get the heli back in the air, and let your research then in time decide to upgrade to better in which I would do.

Resetting the position of the linkage, just make sure your trim on your TX is centered, and because your servo arm is off, all you do is just 'arm your heli', and the servo will then center. put your arm back on, so it's at a 90 deg angle (For equal throw) like your others. I arm the heli to center my servo, then I disarm the heli so as not to accidently hit the throttle on the TX...Lol..

Hope this helps a little. I'am terrible at explaining things, but I figure I'd bump this up to the top for ya. Lots of vets here that will hopefully give ya a suggestion for upgrading your servo's.

Good Luck !


-- Jeff

Thanks, Jeff.

I actually went to and arts & crafts store and bought some wooden dowels and styro balls to make up some training skids. I don't think the CX training gear will work because it's smaller, but when I hit my LHS later today I may have a look.

Also, do, or anyone else know if the gear set in the DS75 is the same as the S75? My LHS has plenty of the S75 gear sets in stock, but since they're different part numbers, I'm guessing it's probably different. The RC Heli tech on the phone says he's not expecting any B400 parts in until the new year, and says sometimes they use different part numbers to track what the items are being purchased for (even though they may be the same parts as another heli).

I know the S75 and the DS75 use the same clear case. I'm hoping the gears are the same, but likely won't be... I'll have to drive the 45 minutes to the LHS to find out, though.

- brian

Brian--

Interesting on what ya find out about the differences in the two. However, I'am betting that the gears are the same between the two. It seems the one ya got is a digital servo, and the S75's are not. I bet that's the only diff. (Guessing) To keep manufacturing costs down for horizon, it looks like they might have left the gears the same, but differences in the electronics part. Let us know what ya find out...

Also here is a little better explanation of your servo placement:


Now this is a CRITICAL step.

1. Turn on transmitter.

2. Plug in the battery on the helicopter.

3. Wait for the gyro to initialize, and the servos to center.

4. Unplug the battery on the helicopter.

5. Turn off the transmitter.

The main reason for doing this is so that the servos are centered before making adjustments on the helicopter in the next section.

If at anytime you move a servo arm. REDO the above centering procedures. If you move onto the next section without doing this, the helicopter will not be set up correctly.


Good luck with your new adventures,


-- Jeff

Torquestar,

J-MICHAEL is leading you down the right road with some good informations. I've got a couple things for you to keep in mind. When you go to the hobby shop, if you haven't done so already. Take the servo with you, I'm betting like J-MICHAEL that the gear sets are the same.

Here's the specs on a S75 servo, I couldn't find any on the DS75H anywhere.
E-fliteEFLRS75
Type: Sub-Micro
Torque: 17.2 oz/in @ 4.8V
Speed: .12 sec/60 deg @ 4.8V
Connector Type: Universal "S" Type
Dimensions: .90 x .45 x .94 in
Weight: .26 oz

Reason I posted this is to let you know that you don't want to mix and match servos, unless they have the same specifications. The biggest concern is torque and speed. If servos are out of balance spec. wise, it can cause some major heli control problems. IE.. one servo moving faster than the other. Ya, don't want that. So don't let them sell ya a Futaba, Jr or any other servo that isn't exactly the same specifications.

On another note, if the heli tipped over to the left, and you mentioned that you didn't have any right stick input. The carpeting may have had some input to that. But I'm betting on the difference from the CX coaxial, to the B 400. The standard collective pitch helis will want to go to the left on lift off. You need to have some right stick input (to the right) to counter act this tendency. Once off the ground it will be okay. Also, once you're hovering the heli may seem to be tilted to the left a couple of degrees, this is also normal.

Hope this helps and let me and Jeff know how you're doing or need any more help,

Dave / Choppersrule

Thank-you Dave ! I swear I've learned more from you than anything, or anybody since I've been adventuring down the heli road...I know there is a lot of folks that think the same, along with the 'silent' ones too...Your the icing on the cake. please don't go anywhere soon, I have sooooooo much still to learn....

Take care of yourself,

-- Jeff

Jeff,

Thanks for the kind words, love to help folks out when I can. Google.com is my main source of information, much quicker than checking all the forums or waiting for response from a new post. Another, learning curve, data research.

Go have some fun, then hit the books.

Dave / Choppersrule
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Unfortunately the gears were different. not by much, but any variance is going to screw things up.

Doesn't look like he's expecting parts to come in until the end of january.

I don't know how much of gear with the missing teeth is engaged during movement so I might try turning it so the broken side is opposite the meshing gear.

i'll also start checking online for suppliers with parts in stock.

Brian--

Sorry to hear about that...However, don't give up hope. Try and look on-line at some of the more popular sites, and see if anyone is carrying them in stock. Not sure how many 'spare' parts there are if any floating around for the new 400, but I would hope there might be some somewhere. Worst case scenario, and if patience kills ya like it does me, then maybe upgrading ALL of your cyclic servo's might be sooner than you thought...

Keep us posted. I'am hoping you will get some input for a set of some good ones for your 400.

Have a good one,


-- Jeff

Torquestar,

YES, you can do that. Turn the gear with broken teeth 180 degrees from where its at.
Also, with any new heli on the market, parts are gonna be hard to find for awhile. Try to google the part number.

Best of luck,

Dave / Choppersrule
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Horizon Hobby has many parts listed already, if they still have a part as "backordered" then I doubt anyone has it.

I also know that HotHeli.com has a large selection of parts, not sure if their on the website yet.

Ray--

I'am afraid your right...Just got done looking on about 6 of the more popular vendors, and NOTHING.... So FYI: When ya do get yours in a few days, hover carefully !

Take care,

-- Jeff

Jeff,

Any recommendations on digital servo replacements? I don't mind replacing the current ones. Especially if I can find units with metal gears!

It seems the servo gear got damaged too easily for such a minor crash.

Where's the next weakest link once you have metal servo gears? Linkage rods?

- brian

I don't know if theres any truth to it, but a nearby HS had told me on friday that he got the blade 400 and "a bunch of spare parts".

He's closed this weekend but i'll be calling him tomorrow.

Torquestar,

Futaba and Jr make great servos, just make sure that the dimensions of the servo case are the same. If you replace all of them, you don't HAVE to get the DS(Digital Servo), although they do respond much quicker than the analog servos. Just a little research will fit the bill. Next weakest link, hmmmmm, that would be an educated guess. Seriously, it all depends on how you crash.

Blades, spindle/feathering shaft(getting bent), and small rotor head parts are the most likely. I don't have a B400 or Belt-Cp YET.
I plan on getting one of each next summer just to check 'em out.

Dave / Choppersrule
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I just checked Horizon and both the gear set and the servo itself are still on backorder, or in laymans terms, unavailable.

But contrary to what was stated above, the DS75 and DS75H both use the same gear set.
Horizon has it listed as "Gear Set DS75/DS75H"

The DS75 and DS75H both use the same gear sets, but aren't the same as the S75 (analog) servo gears, which are available now, unfortunately.

Since it looks like it's going to be impossible to get ahold of the digital DS75 servos right now, I've got another noob question. Can I buy 3-4 of the analog S75 servos and temporarily replace the DS75's?

Would something like that even be compatible?

Torquestar,

Yes, you could replace the DS75's with the S75's. You could leave the tail servo (DS75) installed. And just replace the three servos for the swashplate. Here's an alternative servo that is exactly the same size as the S75. ESKY EK2-0500 mini servo $5.95 each.
They are the standard servo on the Honey Bee King 2 and work very well.

Here's a web site: http://www.tedani.com/esky-ek20500-m...rvo-p-514.html

Dave / Choppersrule
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Thanks, Dave!

For educational purposes, what's the difference between the analog and digital servos? And how can analog servos work in place of digitals?
And lastly, it looks like the Esky servo has a little more torque over the E-flite version. I would imagine that's a good thing?

Torquestar,

Here's a link that will give you the difference between the analog and digital servos. The digital servos have a microprossor in them, and they are alway on. Analog servos only draw current when you move the sticks. And more torque is a good things.

About half way down the page, http://www.misbehavin-rc.com/pit-lan...ifferences.asp

Dave / Choppersrule
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Thanks, Dave.

Hopefully this will work out, because Horizon Hobby lists the DS75 servos unavailable until March 2008 now! And the Gear sets for the DS75 won't be available until late Jan 2008.

Ugh...

Went to the LHS and got a few S75 servos. Replaced the one bad servo and eyeballed the swashplate to a neutral position before screwing down the servo arm. Spooled it up, and the whole heli drifted straight left like the rotors were tilted in that direction. Unhooked the battery, powered it down, disconnected the ball link, unscrewed the end a turn, and re-hooked it up. Looks more neutral and no drift when it spools up.

I made some home made "training gear" with some wooden dowels, a small block of wood ( to connect them all in the center), some wood glue and some styrofoam balls. I used some masking tape to hold the thing to the skids and tried it out. So far, looks like it's going to work great. Can't wait to try it out tomorrow.

Is there anything technically "bad" in running one analog servo with the rest being digital? I know it'll act differently, but in all honesty, it seemed to act no different than the other servos. I'd rather not replace the other servos if I don't really HAVE to...

Torquestar--

Your starting to scare me.......!!! I've heard bad things in flight doing that combo..FYI...I would replace all of the cyclic's with the same.

-- Jeff

Torquestar,

If it's in the budget, change them all to S75, for now, better safe than sorry. Then save some change and get the DS servos when available. It's not recommended to mix servos. Just an FYI.

Hope ya had a good Christmas,
Dave / Choppersrule
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