A couple of kits on the way...

Sorry I haven’t had any updates in a while, was out traveling for most of June.  I’ve been to the track a few times, dialing in my 22T 2.0 and got it working pretty good.

In the meantime, I ordered a couple of kits from Tower.  I have an Associated RC10B6 on order, hopefully that will get here in a couple of weeks.  I’ll most likely keep the B5M around for a while for my son to race with, while I move on to the B6.

Also I decided to get my first retro kit, the re-release of the Tamiya Hornet.  I’ve always wanted a Tamiya since I was a little kid, and my neighbor has an original Frog that he’s updated to modern electronics and we kicked around the idea of racing on the street or at the local park.  I bought the 30th anniversary of the Hornet with the black metallic body.  Looking forward to building it!

I figured the Hornet would also be a cheap and easy kit for my kids to build, so I’m going to let them have a crack at it.  I’m strongly considering starting some YouTube videos of the kits I buy, build and test, we’ll see how that goes.  I don’t really have much in the way of video equipment or a studio to record them in, but I’ll figure something out.

Hope you’re having a good summer, look for some new reviews soon!

TLR 3-gear transmission initial thoughts

I finally got a chance to bring the car to the track to test out the new 3-gear transmission.  I was able to run 5 packs through it, enough to get some thoughts on the changes it brings to the car.

The main difference is definitely less fore and aft pitch.  Under acceleration there is less weight transfer to the rear, and under braking less weight transfer to the front.  In general what this means is that the car is more responsive.  I’m not sure if I was able to carry more corner speed – the track had a new layout I had never driven on before, so it was hard to tell.

The downside to the less weight transfer was that when the track was dry and dusty, there wasn’t as much traction under acceleration.  I had to lower the front roll center a little bit also to get a little more front end traction under corner entrance.

Jumping is another area that changed – the car seems to jump even flatter – which is remarkable for a car that jumps very flat already, but it is very neutral in the air.  You can still control pitch in the air.  I didn’t notice more or less control in the air – it might react a little less, but nothing that seemed overly substantial.

Something that I don’t see mentioned is that my throttle seemed more connected to the wheels than before.  I think with less slack in the drivetrain, the throttle is more responsive and seems crisper and more accurate than before.  Acceleration is slightly improved IMO.

Overall a good mod and definitely worth the $25 for spec racing.  Frank Root’s Nationals setup seems to work better with the 3-gear, although I still have my car setup with a little more roll than his.  The middle hole on the rear arm is super-dialed!

Slash race upgrades 6/11/16

I changed my mind on the order of importance of upgrades for the Slash 4x4 assuming you want to compete.

Here’s my revised list on what I think is important.  It kind of assumes high-traction indoor clay, but the order is the same for most track types.

• LCG chassis
• Tires
• Faster/stronger servo
• STRC aluminum steering rack
• Vented body
• Correct shocks/springs/oil
• Center diff
  
• Rear swaybar
• Good radio

That’s pretty much all you need.  Notice I didn’t say a new motor, the stock Velineon is fairly fast, and if you get to the point where you need to change that, you don’t need to be reading this list anymore.

Shock mounting positions

I swear, this is the most confusing and least understood part of RC car tuning.  I’ve spent a lot of time reading about shock positions and tuning and thinking about what is actually happening, and came to the realization that there are two things going on that are often confused, but actually having separate effects.

For the shocks (front or rear, it doesn’t matter), there are obviously different holes on the shock tower that you can mount them to, and also different holes on the arms that you can mount them to.

Ignore all of that for now, it’s more important to internalize two concepts:

1. Laid down vs. Upright shock

A laid down shock has a more progressive spring and damping characteristic.  When it’s more horizontal, the shock starts out soft and then builds up towards firm as it gets compressed.  That’s because the angle is changing as it is being compressed and starts out horizontal and moves towards more vertical.

A more vertical shock acts more linearly and tends to be more medium-firm the whole stroke through.

2. Shock spaced closer or further from the fulcrum (hingepin)

If you look at the way the arm and shock is designed, it is basically a mechanical lever.  The hingepin is the fulcrum, and the arm moves towards the shock tower as the car rolls in a corner (well, the shock tower is actually moving towards the arm, but it’s the same thing), or as the wheel deflects from bumps and jumps.

The closer the shock is mounted to the fulcrum, the more leverage the arm has on the shock and so it will feel softer.  The further away the shock is mounted, the less leverage it has and the shock will feel more firm.  Now I’m talking total spacing, moving the entire shock (both top and bottom) towards or away from the fulcrum.

With that out of the way, you’ll realize that when you change a shock mounting position, you’re actually affecting BOTH of these concepts simultaneously.  It’s very difficult to lay the shock down more without moving it closer or further from the fulcrum.  When you move the top shock position inward on the shock tower, you are both laying down the shock more AND moving it closer to the fulcrum.  Similarly when you move the bottom shock position out on the arm, you are laying down the shock more AND moving it further from the fulcrum.

It’s very difficult to isolate only one of these factors, as moving a shock position will change both things.  Theoretically, you could simultaneously move the shock in on the tower and out on the arm, which would lay it down more and make it more progressive, but keep the overall shock position roughly the same and keep the same overall stiffness.

This is the first time I think anyone has tried to explain what is going on.  Usually they just say “doing X will make the shock softer” or “doing Y will make it harder”, but almost every time someone says that, they completely contradict what someone else says.

Hopefully this post clarifies some of that confusion.  It was seriously an amazing moment of clarity for me when I figured it out.

TLR 22 3-gear transmission conversion (TLR332056) install

Over the weekend a new TLR product came, and I got a chance to put in the new 3-gear transmission kit for the TLR 22 2.0 series of vehicles.  This fits the 2.0 buggy, truck, and short course.

The installation went pretty smoothly, the only hard part is getting some of the bearings out of the old transmission.  I was concerned that it might not fit the Exotek chassis, but there was only one small thing to watch out for.  The spacer between the transmission and the motor plate has a 0.5mm gap.

I used a small blue washer to space it out.

The hole for the rubber slipper cover grommet is also smaller and more oval for some reason.  A bit tight to put in, but I didn’t have to ream it out or anything.

Plastics are a little grainier looking also.  I would assume they are the same material, so not sure if this is due to wear or if they actually changed it.  Old one on top, new one on the bottom.

Weight might be 1 gram heavier, my scale is not super accurate.  Old and new weights:

The last thing is that there is a little bit less room to tuck the
motor up against the transmission.  On the 4-gear, I used a 21/76
gearing combination, but that won’t fit with the 3-gear.  22/76 is the
smallest combo you can use, it just barely fits.

I didn’t get a chance to
run the car today, the next post will give my first impressions using
the new transmission.