Servo Saver Setup

[BlackBeard]

Hello,

I'm having issues with this servo saver which I don't fully understand...after my previous "oh, my dampers haven't got oil in them" episode of embarrassing noob-ness, though, I'm willing to bet I'm doing something wrong (again)...

It's a basic two-part servo-saver, with a collet the bolt goes through, which also acts as a space to allow the arm-part to turn relative to the splined base.  You can see in the picture, though, it doesn't spring back properly and that amount of play gives very sloppy steering ☹️

There seems to be two issues, here; one is that there's a lot of play between the spring and the upper/lower parts.  The other issue is that the collet seems to cause too much friction, stopping the upper part moving relative to the lower part.  I've greased it up, which has improved it, but shimming it makes the upper part too loose...

Can I fix this, or is it just rubbish?

Thanks for your help 👍

[BlackBeard]

...the image size limit got me again.  Here's all the bits of the servo-saver, with the spring(s) on the base.  There's not an awful lot to adjust!

[BuggyDad]

42 minutes ago, BlackBeard said:

 

Is that centred? It looks like the spring isn't tight enough to hold it firm at centre and therefore there would be play? I wonder if the springs could be removed and then somehow bent in tighter? 

I had looked at similar savers myself on eBay or similar but recall seeing feedback that they are sloppy, which is a shame because it's a part that I think suits having metal parts. 

The other classic issue with saver setup is to tighten the servo screw a bit too much. The saver needs free movement so that it'll spring straight back easily when it does get activated. The advice to achieve that is to use a little Threadlock on the screw, then to back it off a little from tight, or only do it up sort of finger tight.

If slop is inherent to this saver though, I would replace with either a Tamiya high torque one or a 3racing equivalent (essentially the same, just cheaper):

https://www.rcjaz.co.uk/3racing-sakura-d4-servo-saver-ver2-3racshamuv2-p-90070798.html

They're plastic, and as I said I'd be interested to see them in aluminium, but they work well and are in very common use. I see the new 3racing V2 one offers a single joint horn as well, which is nice. I've only used V1s. 

[BlackBeard]

Thanks for your thoughts - much appreciated!  Unfortunately, the bend of the spring (the radius) is set by the aluminium parts, so bending it doesn't have any effect; it needs to be longer than it is by about 1mm...

Thanks for the links to the better savers - good old RCJaz 👍. It's a pity I can't buy just a better spring...has anybody ever tried making one?

[Heavy Duty TLT]

Check something out for me, tighten the top hat without the C springs installed.  The horn should move freely.  if not, then you'd need a little bit of a spacer between the top hat and the bottom splined half.  As for the C spring, maybe make out of some tubing?

[BlackBeard]

Thanks for your help with this.  Without the c-spring, there is, just, enough clearance for the upper and lower parts to move relative to each other.  I've had to grease the collet to stop it jamming both parts together, so the main problem now is the c-spring being too small.

I wondered about cutting a piece of tubing to make a new spring, but I'm not convinced it wouldn't just bend rather than spring back.

I've got a Tamiya 51000 on order, so I'll either just use that or see if the springs from it fit the servo saver I've already got.

[Heavy Duty TLT]

I have the similar problem with off brand Chinese "high torque" servo saver, but my issue was the top hat and bottom half were binding against the servo horn when the screw is torqued down on the servo splined shaft.  I had to place a plastic spacer to free it up.  But still, the C-Spring wasn't strong enough for my Juggernaut's big tires, and makes the truck really clumsy...    I'm either going with just a solid aluminum servo horn that came with the servos, or save up for a good quality one.  My servos are the 9imod 60KG HV with brushless motor.

[BlackBeard]

It's the c-spring seems to be the issue for me, too.  What servo saver are you planning on buying?

[markbt73]

The trouble with this servo-saver design, and it applies to Tamiya's kit-supplied units as well, is that if there is any gap at all between the ends of the C-shaped spring amd the two nubs on the top and bottom halves, there will be play in it, and there isn't a thing you can do about it. It's just a lousy design.

My advice is to get rid of it, and spend far less on a Kimbrough (name brand only!) servo saver. They're made of nylon and essentially unbreakable (I have some going on 30 years old), and are completely slop-free. They use an internal coil spring instead of that external c-shape, so the spring always holds the two halves together tightly to take up the gap.

[BuggyDad]

22 minutes ago, markbt73 said:

The trouble with this servo-saver design, and it applies to Tamiya's kit-supplied units as well, is that if there is any gap at all between the ends of the C-shaped spring amd the two nubs on the top and bottom halves, there will be play in it, and there isn't a thing you can do about it. It's just a lousy design.

My advice is to get rid of it, and spend far less on a Kimbrough (name brand only!) servo saver. They're made of nylon and essentially unbreakable (I have some going on 30 years old), and are completely slop-free. They use an internal coil spring instead of that external c-shape, so the spring always holds the two halves together tightly to take up the gap.

You triggered me to go and look up what's in a Kimbrough Saver. They're made by Mr K in a shed with an old manual machine! 

I'm getting me some of them in my life.*

I too am a bit fed up by the C spring design, whoever's they are.

*I've got one actually, and it's been great, over more running than any other car/saver I have, I just hadn't appreciated what was in it. It's gone unnoticed for 2 years in my DT-03, which, now I think about it, is impressive for a servo Saver.

Coincidentally, the other day I also ordered some of the Optima Mid steering parts, purely because I like how they've implemented the saving of servos, with an eye on modifying some Tamiya buggy or other to take it. 

[JimBear]

@BuggyDad @markbt73 I've had issues with (various) servo savers on the Rising Fighter - I need to get me a few of the Kimbroughs to try them out. Would the medium size be the right fit?

[BlackBeard]

Thanks for this - the Kimbrough design looks like the way to go!  Now, if I could just figure out how to reduce the bump-steer on this chassis, too...🤔

[BuggyDad]

9 hours ago, JimBear said:

@BuggyDad @markbt73 I've had issues with (various) servo savers on the Rising Fighter - I need to get me a few of the Kimbroughs to try them out. Would the medium size be the right fit?

The one I have is a medium and it seems to work as a suitable replacement for a stock Tamiya 1/10 Saver, size wise. Although I've no experience of any other size, on a quick Google the large ones look much bigger to me. 

 

[gogsyfinnie]

After mucking about with standard kit savers I bulk bought a few small and medium kimborough ones, I too think they are a huge improvement!

[BlackBeard]

What a pain in the bum this is turning into!  I'm still waiting for my large Kimbrough to arrive, but I found a medium in my boxes of bits - the holes are too small for the tie rod bolts I'm using and the holes are too close to the edge to safely drill out.  My Tamiya hi-torque turned up, but the holes are too close together for the tie rod ends to fit next to each other!  Apart from that, it seems quite good.  Hopefully the large Kimbrough will be big enough, otherwise, I'll have to get new tie rods...where will it end?! 

[JimBear]

T-rex patent trolling aside ... I am not sure if what the postman left by the door are the "real deal", these says Schumacher (part number U3940). But they do look nice and sturdy.