Servos and four-wheel steer...

[pritch]

Hi folks

Please see my build thread at New X-Crawler build for more background and pics of my build.

Although crawling for some time I think I'm still quite green when it comes to crawler theory 101 so looking for tips from the pros.

Off the ground my new build is steering fine, but on the ground, when I steer both ends, whichever end is at the front going forwards isn't turning much. If anything it's more noticably affecting the airtronics servo (the stronger of the two) when that is going forwards, which it usually is of course being my front servo.

I had thought it was the servo savers I had on activating, so I replaced those last night with some alloy steering arms from ebay, I think it has helped a bit but still doing it, and the faster the crawler is moving, the worse it is.

When these electrics were on the old pimp cane chassis, the same thing happened, but I had put it down to loose motor brackets and general slop, something I figured the new chassis would cure.

Can anyone help with any suggestions? Thanks!

[benoj]

my best guess would be a bec since you are running 2 servos. try unhooking the rear servo and see if the front servo still struggles to steer.

[Charlie-III]

Originally Posted by benoj

My best guess would be a BEC since you are running 2 servos. Try unhooking the rear servo and see if the front servo still struggles to steer.

+1, a BEC will likely fix your issue.

Questions though:
1-With the servos disconnected from the steering linkage, does the steering work well or is it stiff?
2-Does the ESC or RX die when the steering slows down?
3-Does the issue happen at any time, or after the rig is run for a bit (wondering if the servo is getting hot)
4-What batteries, are they "new" or tired?

[pritch]

Hi Charlie,

steering works well by hand and off the ground, nice and new like it should be.

I am getting some ESC/rx glitching indoors in particular (haven't done much outdoor testing yet but that's all going to change this week as I'm on holiday and have brought it with me

It is happening at pretty much any time so far - servos have never got hot. The batteries are decent 2s lipos from my e-revo collection that I can vouch for. That's a switch from the 3 cells nimh over each axle on the cane - something I wanted to do.

As these symptoms were a bit present on my old chassis too, I too am starting to think the novak rooster bec is maybe not cutting it.

UK crawler guys recommended a 10 amp bec minimum - would you go along with this or do you think I could get away with a 5 amp sbec?

Thanks

[Charlie-III]

pritch, thanks for the replies. It really sounds like you could use a BEC. Most of us use the CC 10A BEC (CC = Castle Creations), it's not big and can supply pretty much all the power you need.
I recommend you wire it direct to the front (larger) servo, only the white/yellow signal wire goes to the RX.

[pritch]

Took it out properly for the first time today. Generally speaking I was quite impressed for a first run, but there's still a ways to go!

I had some of the usual glitching from the Rooster when I steered, and a lot more glitching in reverse, in fact it didn't really like going in reverse at all without glitching, even when I wasn't steering - this still sound bec-related to you?

I think I'm gonna get me a Turnigy 5amp (peak) ubec to start with. Reason being they are only £5 on ebay and as it will be my first install I'll see if I can wire one in no probs. If that doesn't cut it I will find a seller who has the cc bec in stock.

I know I'm sort of ignoring good advice - thing is cc bec is £20 and I just won't be able to not get the castle link if I get the cc bec = another £20. I know for sure now that this x-crawler is going to need different shocks... the pockets are only so deep!!! ;)