Budget Buster

[Mad Ax]

Thought I'd best post an update here.  No pics I'm afraid, and the video I took came out terrible, but I have at last run the truck.

Last weekend I fitted the all-new Traxxas LiPo-safe ESC and got it set up for LiPo compatibility, fwd-rev operation and full power.  It was too late to go for a run but I took it to a local bash site on Monday lunchtime for a blast in the sun.

The truck actually runs really well now that I'm using solid servo horns.  Switching between 4ws and 2ws from the handset is awesome, giving control at speed and tighter turning radius when I'm navigating tighter areas.  Even with the diffs locked, it'll turn fairly tight.  I still have a bit of trimming to do on one servo horn as it fouls the wheel on full lock.

Handling isn't at all bad either.  The shocks are a bit too stiff but have just enough give to provide some compliance on jumps.  They just need to be a bit smoother, there's a chance I'll upgrade to GMade shocks fairly soon.  The shocks I have seem to be an odd diameter and I don't have any softer springs that will fit.

The downside is that the whole thing seems really, really slow.  I might have to check the speedo setup again to make sure it's on full-power mode and not training mode.  I was thinking it needed bigger pinions to increase the top speed, but it doesn't seem to accelerate that hard either.

When I was running a similar wheelbase on a much heavier TXT/Clod hybrid using dodgy 14.4v NIMH batteries, HPI GT speedo and HPI 550 motors, it would easily wheelstand off the throttle and generally behave like a whirlwind.  Now, using a pair of 3250mah LiPos and Traxxas Titan motors, if feels flat and dull.  It's a rare case of a custom truck's handling completely outpacing it's speed  

I'll double-check the speedo settings and give it another run when I have time, but it could just be that those Traxxas motors aren't as hot as the old HPIs.  I might have to consider other 550 motor options - feel free to recommend some!

[Mad Ax]

OK, so I was a bit disappointed after the inaugural run and the truck has languished under a bench in the garage ever since.  I did a bit of digging on clodtalk.com and read up that the Traxxas Titans are often considered a bit lacklustre unless geared right up to make the most of their torque.  I don't have space to install an adjustable gear carrier, so the Titans have been pulled out in favour of the wickedly-fast GT550s that I was using on these axles many years ago.

I hoped it was going to be a 10 minute job to swap them over, but it seems one motor has a broken connector tab and the other a failed bearing.  Neither really had much use from new but both had a fairly hard life under my TXT/Clod hybrid, bouncing through puddles, sucking up 14.4v power and getting minimal maintenance.  The beauty with these old brushed 550s is that they're dirt cheap, so a new set has been ordered and should be with me soon.  Also got me a pair of Robinson Racing pinions on the way, since I've been running the standard Tamiya cheese ones since I first built the axles so long ago.  With new gears installed and a whole new truck almost ready to race, it seems a shame to be using old, soft pinions...

I was surprised by how stable the truck was on its first proper run, even if the speed wasn't right up there.  The shocks seemed too stiff with a bit too much stiction due to the slight angle in the non-pivoting tops, but it soaked up the bumps well, didn't waggle its wheels in the air like it would have done with softer shocks, and naturally those big tyres help a lot in protecting the axles from impacts.  Still, I fancy a new set of proper shocks for it, so I'll try to order some nicer GMades or other good-quality shockers today if I can find someone with a set in stock  

[Mad Ax]

Update - got the GT550s fitted a couple of days ago but still having issues with acceleration and speed not being what I thought it should be, however the batteries hadn't been topped off since the last run and the speedo was showing a flashing red light, so I had to assume it had gone into failsafe mode.  I recharged both packs, checked the speedo was configured in the proper mode, and took it for a spin this lunch.

Now got an immediate improvement on acceleration and speed, but couldn't get it to last long before that odd red flashing light came on again.  Might have to check the Traxxas documentation but it seems once the red light has started to flash, I can't turn the speedo off - but I can carry on driving around.  Very bizarre.

It's entirely possible my old Core RC 3250 packs don't have the punch for the 550 cans and the speedo is going into failsafe mode after a heavy launch.  I'm not really sure how it works.  I'll charge up some newer packs with a higher C rating and give them a try.

In other news, the modified servo mounts don't seem to be tough enough to survive an impact without a servo saver.  They're bending!  I'll have to track down a servo saver that will work in a hi-torque situation (the regular Kimbros I tried just flopped around everywhere) but able to absorb an impact with a catch fence.  Once I'm happy the servo saver is doing its job I'll modify or re-make the servo brackets with some triangulation to stop them bending.

This really is one of those "should have bought an E-maxx" situations

[Saito2]

19 hours ago, Mad Ax said:

This really is one of those "should have bought an E-maxx" situations

Yeah, but an E-maxx isn't a true solid axle monster truck.