What spur gears compatible with ECX 2WD cars?

i_r_beej

i_r_beej

Well-Known Member
Messages
993
Hey all!

I just installed a 17.5t brushless motor (for stock racing) and I need to change the spur gear on my ECX Boost to something smaller (69-72 teeth). Does anyone know what other brands would work as a direct replacement (or with a minimum of drilling) for the stock ECX 87t spur?

Thanks for any info.
 
I know the Team Associated T4/B4 spurs work but you have to drill out the hole to 5mm (.199 if you insist on medieval units) and don't forget to buy the slipper pad as well. TA has everything from a 66 up to in the 90s.
 
Thanks. Yeah, metric is better. Part of the reason why I detest AE stuff. :D That said, none of my drill bits are metric sized!
 
I installed a 69t (48p) Associated spur last night with a 33t pinion. Even after lengthening the adjustable motor mount slot the mesh is just a tiny bit loose. Also, the pinion is so large that it rubs the washers on the motor mount screws! So I have to slide it outboard a little.

I think I'm going to get a 72t Associated spur and that should give me correct mesh.

72/33= 2.18:1
69/33= 2.09:1

Not sure if this will kill me in Stock Buggy class.

I'm going to finish the installation tonight and post a build thread in Drivetrain...
 
Yeah, HR produces steel spurs for ECX 2WD in 81, 83, 85, and 87 teeth. But I don't want to do steel since this is a racing car. Every gram counts! And the ECX Boost totally doesn't need any more weight in the rear.

I've found the Associated spurs for the B4/T4 seem to work really well. My modification (drilling out) of the AE spur was really easy and produced a perfect result.
 
Yes. A 69 spur x 33 pinion with a 17.5t brushless motor (Reedy Sonic M2) makes for a speedy little buggy! However, after a day of racing the spur had suffered a little since the mesh wasn't as close as it should have been. I bought some sanding drums for my Dremel tool and I'm going to grind away some plastic on the transmission housing to see if I can get the motor to slide up closer to the spur.

I mounted a 72t Associated spur and was able to get perfect mesh. 2.18 vs. 2.09 final gear ratio. Not sure if that will hold me back or what. But I'm still working on my driving skills so it's not a big deal yet.
 
Cool I wish I had a racing scene nearby :( there's little incentive to improve your car if you don't have a track. I might dig my own track in the yard some day but it's a lot of work and I'd still be on my own (apart from my son, who's not really a competitive kind of guy).
 
xlDooM said:
Cool I wish I had a racing scene nearby :( there's little incentive to improve your car if you don't have a track. I might dig my own track in the yard some day but it's a lot of work and I'd still be on my own (apart from my son, who's not really a competitive kind of guy).
Click to expand...

I think I'm reading about a guy who has lost his inspiration to go faster and bash harder. I've been driving alone for years, mostly, up until my son got into it recently. But he's still young so he's no competition. Maybe you need a new RC to get your flames roaring again? A new power type (nitro, gas, etc.)? But even if none of that gets you excited, just post on here about the fun you're having and I guarantee we will join in. ;) :)
 
You may be right. The arrma kraton looks pretty nice :D Ever since I pushed down on the exposed chassis in the hobby shop, the smooth feeling of the big bore dampers has stayed with me. There's just something really nice about that thing.

The circuit 4wd bl had me similarly excited. Something about the packaging of the components in those things.

I could of course buy another black/green amp, put a cheap (turnigy or leopard?) brushless system in it and keep it in my car trunk, pretend to the wife there's only one...
 
xlDooM said:
You may be right. The arrma kraton looks pretty nice :D Ever since I pushed down on the exposed chassis in the hobby shop, the smooth feeling of the big bore dampers has stayed with me. There's just something really nice about that thing.

The circuit 4wd bl had me similarly excited. Something about the packaging of the components in those things.

I could of course buy another black/green amp, put a cheap (turnigy or leopard?) brushless system in it and keep it in my car trunk, pretend to the wife there's only one...
Click to expand...

I just picked up a BL circuit. I'll let you know how it does, I'm rather excited about it.

Since you mention Arrma, have you seen the new Nero? It looks like a fun rig.

http://www.arrma-rc.com/nero/
 
I hadn't, but it looks real good. It's a bit out of my budget though, I'm hoping it will push the Kraton price down further :D
 
Okay, here's a few photos of my installation:

Parts! The Associated parts that are compatible with 2WD ECX cars come from the B4 (buggy) and T4 (truck). Associated makes a 69t, 72t, and 75t spur that will fit ECX 2WD. I'm starting with 69t as a 69/33 spur/pinion combination seemed to be the most common combination at my local track. (The Associated B5 and TLR 22 cars seemed to have an almost identical transmission ratio to the ECX Boost (and all ECX 2WD). (2.6:1 if you're curious)

Anyway...That's a 13/64" drill bit. Fortunately tool manufacturers are being swayed by logic and have started to include metric dimensions. So this drill bit is 5.2mm. The input shaft is 5mm so this is perfect. I've noticed that most of the softer plastics used in (RTR/less expensive) RC cars is somewhat "elastic" in that after working it shrinks. So I was confident that the extra .2mm would not be a problem. Drilling the input shaft hole out was a big non-issue and resulted in a PERFEFCT fit!

ecx-ae-spur-1-parts.jpg

Once the Associated spur was drilled out, installation of the slipper pads was a bit fiddly, but uncomplicated. The spur was nicely concentric so there were no crazy mesh problems looming.

ecx-ae-spur-2-installed.jpg

I knew that I'd need to drill out the adjustable motor mount screw to allow the motor to swing in closer to the spur. Carefully working the drill in the slot, I lengthened it to get the motor as close as I could. In the photo below you can see that the mesh is not good. The motor housing is contacting the transmission housing on the other side. I'm going to have to use a small sanding drum and see if I can remove material to allow the motor to move even closer. After a day of racing the 69t spur had evidently been slipping/jumping against the pinion as all the teeth were rough. Fortunately none are broken so I think I can salvage it (providing I can get the motor to move closer to the spur). For the time being I am running a 72t Associated spur and am able to achieve perfect mesh.

ecx-ae-spur-3-mesh.jpg

As an aside, I realize that I could probably just go up a tooth on the pinion (from 33 to 34) but I would likely cause the motor to work too hard (it already gets up above 130F/54C degrees) after 15 minutes of racing. I would also face more clearance issues with the motor mount screws.

If you look closely you can see how the teeth of the pinion overlap the star lock washer and stock washer underneath it. This setup forced me to move the pinion out about 1mm so that it wasn't full engaged with the spur.

ecx-ae-spur-4-pinionoffset.jpg

I solved this problem by purchasing some tiny split-ring lock washers that fit perfectly under the diameter of the head of the motor mount screws. I used a smaller diameter washer from my Dynamite SS fastener kit and was able to move the pinion back inboard so that it just cleared the mounting screws and was still able to engage fully with the spur. I just think a 34t pinion would just cause more problems.

The new, higher gearing combined with the torquey 17.5t brushed motor (Reedy Sonic Mach2) makes for a speedy stock buggy. Look out you Associated B5 turkeys, my ECX Boost is gunning for you! :)
 
skip the drill bit, use a body reamer instead. little by little till it fits kinda snug. drill bit could take out too much material too fast. You only need to remove a tiny bit of material and using a drill bit could off set the hole causing problems. Plus all you bashers out there - use the 32P AE gears instead of the 48P. You'll never strip a spur again. Remember most time a spur strip in a ECX 2WD is from chassis flex ( you can move the motor away from the spur just from a hard hit or rough landing) Have witnessed the rear of my Torment twisting after jumping over my head. Softer plastic is basher friendly.
 

Latest posts

Members online

No members online now.
Total: 172 (members: 0, guests: 172)
Back
Top