mjwills

I picked up the Basher Sabertooth before Christmas. I am having great fun with it.

An issue I had a few days back is that the steering locked to one side. This occurred racing around on a soccer field (no jumps etc). It occurred around the same time as the car flipped on its side and cartwheeled (I am not sure if that caused the problem, or was a result of the problem). I removed the horn / arm (not sure its name - the black thing you screw onto the servo), and centered it and it worked briefly but then locked to one side again. The screw in the horn was already loose after just a minute or two.

I tried some thread locker around the screw. I left it to cure overnight. The next day it stayed centered for about 5 minutes, then the old problem was back (fiddling with steering trim made it better, but not fully centered) . The screw doesn't seem loose though, so perhaps a different issue than previously?

I centered it again, and tried thread locker again. Once again, (48 hours later when I drove it) it shifted off center within a few minutes..

I have images - but it won't let me upload them here until I have 10 posts. The gears inside the servo look OK, but the metal gear outside the servo doesn't look great (it is hard to see in the picture, but the picture with me holding the servo shows the metal gear quite 'smooth' on one side, which I am guessing can't be a good thing).

Does anyone have any advice? Do I need to buy a new horn / arm (and if so, which one)? And / or a new servo? I presume I could buy a TS-910 or the like and replace it - but if I do that, how do I reduce the odds of the same thing happening again?

RustyUs

If the servo saver is good working order (possibly too good), then I would think you may have stripped/damaged some teeth on a gear inside the servo. Anyway, I'd remove the servo horn and start there; making sure it's not just the horn that is stripped. While the steering linkage is not connected to the servo, make sure you have no binding anywhere while moving the linkage by hand.

Edit: I re-read your post and seen you had looked at the gears inside, and they were fine.

RustyUs

For a "middle of the road" servo, I'd be putting something like a Power HD WP-23KG servo in a 1/8 scale truggy. Reason being, that Power HD servo has titanium and steel gears whereas most lower cost metal gear servos have softer metal gears i.e., aluminum, copper, or brass. As a bonus, that servo has replacement gear set available for it. Also, I'd recommend a clamping style servo horn. I find the clamping style horns are easier to work with and they have better servo spline gripping power. Sometimes the molded plastic horns have to be manhandled on. Because of plastics and their molding not being perfect, I know I had to double/triple check tooth count, because some horns felt too tight. When shopping for servos, and horns/arms just make sure of the number of teeth on the servo's output spline.

mjwills

Thanks - that was super helpful info from you - thanks!

It looks like I can get the servo you recommended from ebay to ship to Australia for about $45 AUD ( http://www.ebay.com.au/itm/Power-HD-...t/323410241336 which is very cheap) excluding the aluminum horn. The combo you found would be about $72 AUD ish - the joys of shipping to Australia!). Thanks for the recommendation. I'll have a look around banggood and ebay etc and see if I can find an appropriate aluminium horn (would http://www.ebay.com.au/itm/25T-Alloy...X/123076934684 be OK?)/

BTW, these are the images I tried to link to earlier - photos.app.goo.gl/2SP2f45uGKj69jWB8 (put https at the start).

What is it likely that I did wrong? How would I avoid it happening again? Or do you think the new servo, coupled with an aluminium horn, will solve the issue all by itself?

RustyUs

I don't know that you did anything wrong other than maybe getting some thread lock on a plastic servo arm. Certain thread lockers attack plastics differently, and may make the plastic brittle. To keep thread lock liquid from getting all over the place, I would put a dab of thread lock on the tip of a toothpick, and then coating the servo output spline threads (where you insert servo horn screw). If thread lock is used along with a metal servo horn, the removal of the screw(s) is much easier when heating up/melting the thread lock with a "jet flame mini torch" lighter found at local convenience/department stores...


Those images helped a lot. The pic, where you holding the servo horn, the camera is focused on your finger, but it does (from what I can tell) look like the teeth inside are worn down. I'd put a clamping servo horn on the stock Sabertooth's servo and have a go at it. When you do get a new horn/arm, just make sure to power up the servo, and have your transmitter's steering trim centered before putting on the new horn. You want to know the servo's neutral position as you are hooking up the steering linkage.

I don't think you'll need a new servo, but it's always nice to have a backup/spare servo around.

How many teeth does the stock servo have? That I don't know. The horn, that you linked above, looks great. Steering linkages vary from RC to RC. The way the ball studs/linkage mounts on servo arm will determine best servo horn design. Sometimes you will need an arm that allows more mounting room underneath the horn.

mjwills

Again, awesome info - thanks. I'll give the new horn a go and keep in mind your thread locker info.

Thanks for the centering tip - I was doing that already, but good to be reminded.

Much appreciated! Thanks for your help.

seedygreenute

Probably nothing you did .
If you havn't checked it out ... Aussie RC Playground on youtube has some Sabretooth videos .
Seller rcboyz on ebay has good shipping rates to Oz from USA for general parts like wheels or tires .
Seller Plaig Bearings on ebay for bearings , not sure he will have a kit for your model but will have all the right sizes , you just have to messure yours , or check the manual .
In the past Ive got some good prices on batterys from Mild to Wild RC in Brisbane .
Most of your parts will come from Hobbyking unless you can work out what is interchangeable from another model .

mjwills

Yep - thanks. That would encouraged me to get back into RC.

Awesome suggestions, thanks. Yeah so far I've been getting stuff from hobbyking (spare tires, batteries etc), but I've just bought the new servo from ebay and a few horns from aliexpress to try. I'll see how I go!

mjwills

I have installed the Power HD - thanks for the suggestion. It fits in perfectly as a replacement of the old servo.

I tried putting a 25T horn on the old servo, and failed since it wouldn't fit. I am not sure if that is because it wasn't a 25T servo, or because it was stripped. Either way, I removed it and swapped in the Power HD and an aluminium horn.

Now, I have a fresh problem, as shown at photos.app.goo.gl/QEmf3Nh219JgJwYBA

Basically, if I add the aluminium horn then the bit that the horn connects to (not sure its name - let's call it an arm for now) has no nice place to connect. In one of the images you can see it is in roughly the same position, so I can't work out how to connect the two. I could make it work by angling the arm, but it didn't look very stable so I was reluctant to try and drive that around.

The other image is using the stock horn that came with the Power HD (plastic one I presume). That one looks like it will work fine (since it is small enough for the arm to fit underneath it).

So my question is - what should I do here? Should I buy a 'thinner' aluminium arm (and if you could point me to options from banggood or aliexpress etc that would be even more awesome)? Is there a way to connect the arm or the horn some other way? Or should I just use the plastic horn that came with the servo? Or something else?

RustyUs

Trust me, I feel your pain. Finding the right servo horn/arm is not always an easy task. RC platforms have various ways of connecting the steering linkage to the servo. Some steering linkages will mount above, some will mount below the servo arm. I've sometimes spent hours searching for (what I think will work) the correct arm to use. Different servos have their mounting ears located at different heights sometimes as well, and is why kits will come with spacers to raise/lower servo for best position.

Looking at photos of stock Sabertooth, looks like the steering linkage is mounting under the servo arm. Would need to find servo arm that sits high off of servo body, and that doesn't have that extra material under the arm.

RustyUs

I've used these generic non-clamping arms with good success...https://www.ebay.com/itm/Titanium-25...XWA:rk:36:pf:0

When I feel like splurging...https://www.teamassociated.com/parts...orn_25t_20_mm/
https://www.teamassociated.com/parts...n_25t_15_5_mm/

Those linked servo horns above may, or may not, be the best for your situation. I'm just trying to show some examples with the arms offset in the right direction. There have been times when me and Dr. Emel (Dremel tool) go to town...making things happen.

mjwills

Awesome suggestions, thanks. I'll order in some 'thinner' horns and see if they help.