Wednesday, December 5, 2018

MST TCR - It's a touring car, sorta.

I'm going to start this conversation in an unusual place.  The sign of a manufacturer being proud of their product, is their desire to put their name on it.  This is, more or less, the first part of the car I got a good look at.  MST put their logo, on the wheel.  Tamiya doesn't even do that.  At least, all the time.  


Another good clue, is the package of "spare" parts a car comes with.  (yes, I have cats..)  Screws, spring perches, track adjustment pieces, ride height adjustment bits, ball ends, and a 380 size motor adapter! 


So I've burried the lead here, a bit.  Lets go back to the begining.  Here's the box you get, when you order a MST TCR.



Good looking box, it has some decent graphics on it... on the sides that a customer might see when it's on a asian shop shelf.



... wow, I should have cleaned up the dining room table.  But look at that, if it were glossy, you'd assume it was Tamiya.  We'll cover everything listed here in a bit.

Now the other side of the box, shows off this chassis's parlor trick.  It can be built as a FF, MR, or RR drive chassis.  This kit is sold with a FWD body, and the manual details just the FF setup, but.. all the parts are here, we could build it in any of these configurations. 



The car is cheap.  Retail is around $150.  And that includes are very nice Civic body with light buckets and a nice decal set.  Many, maybe all, of the design decisions were based around making the car cheaply. 

The MST TCR is, for lack of another term, a touring car.  But it's a very strange example.  A typical touring car, has a transmission, that then drives a differential, and then two, or four wheels.  They also have independent suspension. Modern touring cars also typically are double deck.  The TCR only hits about half of these points. 

Pan cars, like F1, 1/12 scale, World GT-R, all have direct drive transmissions.  The rear ends are always live axle.  And the cars are usually just a single pan of carbon, or aluminum. While they are somewhat less the rule, 1/12 scale cars typically have the front  ends that are strut type, which you don't see on touring cars. 

I think the best way to examine this, is to dive into the build.

Upon opening the box, you're presented this.



The details on that body are crisp, and as usual, under the body we have all of the juicy bits.



There's really only six or seven bags, and with so few parts, the "lets do this bag by bag" process kinda falls apart.  That said, they did a decent job.  I was never left wondering where my parts were.

The decals for detailing the Civic Body.



Happily, the car also came with a setup sheet.  My first thought upon seeing it was "this is nuts, what is there to setup?  I have a TT01e, and there's just ~nothing~ to do to that car.  I have notes about how I treat the diffs and tires, but there's really nothing else I do to it.  Boy, was I wrong. 



How wrong?  Well, I thought camber was fixed (mostly) turns out they have a factory method for adjusting camber.  They also have a prescribed method for dealing with ride height.  They included a set of 4 spacers to help with ride height as well! 


Oh, look, a differential.  Funnily enough, that's where we start with this build. 


Bag 1, and "Tools" are what we open first.  


Cost savings spot number one.  These parts are all plastic.  Not a complaint.  But look at the orginization here.  Worthy of note, is they provide different grease for the diff balls, and for the thrust bearing.  You also get a spare ball for both the diff, and thrust bearing.

This is also where I ran into my only trouble with the instructions.  Each page of instrucions is mostly just an exploded diagram with labels.  Sadly, the diagram for the diff, made it unclear what side the nut, and thrust bearing went on the diff.  It's clear on this page:



But not, on page one of the manual.  Look at that, eggshell finish paper, color printing, colors used to designate materials.  It's real artwork.  I'm impressed! 

Did I mention that the tools bag had tools in it?  It really does.  They're not "good" tools, but if you're careful, they'll let you build the car. 



If this were a pan car, this would be the whole rear axle.  What makes this unusual, is instead of fittings for wheels at both ends, it has joints to connect to dogbones.  Or.. as is the case in this build, universal joints!  And that's where this car becomes a touring car, instead of a pan car. 

Touring car rules generally state that you need to have 4 wheel independent suspension.  And that's something this car has, even though it's a direct drive type transmission.

Next is to put the bulkheads on the chassis.  We get four.  There are two types.  I have shared this before, but i'm going to say it again.  Buy, and use, a M3 thread forming tap.  And tap all the holes.



They bolt straight onto the chassis.  The screw holes are tapered, so are mostly self centering. 

Evidently, I missed taking pictures of attaching the lower suspension supports.  They just bolt into the sides, with embedded nuts.  For the side with the motor mount, you skip the retention nuts, and just screw directly into the motor mount. 


So my head was convinced this was a touring car at this point.  As most builds look  a lot like this, at this point.  But unlike a conventional dual deck touring car, we're ~almost done~ with the build here. 

The servo mount screams pan car.  Or at least F1 car.  This might be my first real complaint about the car itself.  I dislike taping servos into cars. 



That servo saver, is something to write home about.  It centers solidly, and has a nice strong spring in it.  The plastic is also very stiff, and taps well.  I like it better than almost anything short of x-ray.  It certainly goes together easier.  Unlike a lot of servo savers, it also can't be screwed up by over-tightening the attachment screw.

Wow, I took a bad picture.  But you can see a few things here.  First, another page of the manual.  Now on the bulkheads, and the servo, you can see the toe links.  All of the links (all four!) are detailed in the manual, and have 1:1 scale drawings to compare against, as well as providing measurements so you can do it with calipers.. if you prefer to do it that way.



Both battery mounts are in place.  While the servo mount uses M2.5 bolts, the battery mounts use M3.  Thankfully. 

Ok, lets take a closer look at an assembled end.  I hate when I don't get good pictures of the working bits. 



The hubs are a different plastic.  Speaking of the plastic in this kit, they're filled "something".  I suspect nylon, but not a very high fill percentage.  So they're a bit flexible still.  You can also see the hex hubs.  Which have those "for show" brake disks.  The holes on the front of the hub, are to mount the fashion brake calipers.  You'll note, I left those off. 

You can only barely see it, but the car does come with CV joints.  The only tricky bit with them, is the pivots are tapped on one side.  So check that before you try to install the setscrews. 

While we're here, we can talk about the adjustments that can be done to this suspension setup.  By putting shims between the lower arm, and the bulkhead, you can do fine adjustments of track, and more importantly, camber.  By putting shims under the three balls at the top you can tweak camber gain, and roll center.  By putting a spacer under the front or rear of the arm, you can introduce variable caster. 

If you move the arm to the outer set of holes, you can adjust the amount of caster gain during steering. 

In the front, there's three holes in each hub allowing you to adjust ackerman, and total steering angle.

In the rear, there's something else to tweak.  There's two holes in the hub for the link, and three on the bulkhead.  By changing those mounting holes, you can tweak toe gain or loss. 

Finally, ride height is adjusted by putting shims that go under the bulkheads.  Speaking of shims, there's also 10mm of shims that comes with the car to widen the track.

I suppose this means, that the setup sheet, is far from redundant.  I'm excited to see what setups come out. 

So lets talk about the motor mount.  The spur that comes with the car is about as big as it can get.  The motor mount only has two motor positions.  The car comes with a 15 tooth pinion, I forget the size of the spur.  At this time.. the manual isn't online, and the manual isn't at hand, so I can't quote the spur size.  


This is probably the biggest point of frustration here.  We can't go bigger on the spur, but we can go smaller.  We can't go much bigger.  Switching to 64 pitch, might provide a bit more there....  But really, since this car is only ~really~ legal for USGT, we just need to worry about getting 3.8:1 gearing. 

Speaking of tuning, my car came with silver and green springs, and a complete spring set.


I believe this is a temporary bonus.. but I was quite happy to find it in the package.  Swapping springs is done by a single screw under each hub.  That screw is 12mm long, and provides reinforcement for the sliding part of the kingpin/strut. 


So the bare chassis is 337 grams.  That's super light.  Although without the steering servo, servo mounts, servo saver, and tierods.  I think... this could be less than 1000g all up, as a FWD touring car.  That's F1 territory.  And closing in on 1/12 scale. 

I really suggested that I was going to cover how "to a price" this thing was built to.  I think we can cover that now. 

The parts count on this chassis is tiny.  The upper control arms are all the same part.  The lower control arms are all the same part.  The spherical bearing is all the same part.  The front and rear cages are the same part.  There are two hubs, and you get two sets to get the 4 for the car.  Same for the bulkheads. 

Most of the parts of this car, are the same left right, and front back.  Talk about cost savings! 

Now, the completed car, once you get a servo, and battery in it, sits reasonably well.  But grabbing the car and twisting it, leads to some funny thoughts.  First, the car bends really easily across the middle.  It doesn't have any chassis bits to brace the middle of the car.  While the ends are quite sturdy, between the solid bulkheads and cages. 

It seems that MST has anticipated this.. there's some holes that are conveniently M3 sized, and in good places for bracing the chassis.  This weekends project is going to involve making some braces to put there. 

Also, there's the elephant in the room.  There's no damping. No shocks.  No instructions for applying grease.  No apparent plans for stopping this thing from pogoing around.  I'd love to find out what people might do to control body motion on this car. 

I have another car in my stable, that has essentially no damping.  A TT01e Euro Truck.  And, amazingly, it works just fine. 

There's also that 380 motor adapter.  I'd be surprised if it wasn't included for a ~good~ reason.  But.. I've never seen people intentionally run 380 motors. 

There will be a followup, for this, eventually.  Once I run it....  The plan is to run the car in USGT.  I am anticipating a hilarious mess.  A "quick" car, that's not fast. 






























Monday, November 12, 2018

It's winter, time for miniquads

A R/C racers primer: Notes, and Vocabulary for the new racer.

What you need to know, to go R/C car racing

So you want to go R/C racing.  "I" want you to go R/C car racing.  Sadly, there's a few things in your way.  So lets get those barriers down.

First things first, you need to determine if your car can be race legal.  Most tracks have club racing, where they have a day or two a week, that they'll have organized races.  Because people like "competitive" racing, those races are usually carved up into different classes.   You should call (and I do mean call.) the track and find out what's common, and popular.  They'll also help you find where you can run your car.

This primer is for on-road, but off-road racing is quite similar, with fewer common classes.

There are a few things that determine what class a car would run in.  Body type, weight, allowed tires, motor, esc, and chassis.  That sounds like everything... and it is.  The bulk of differences betwen classes really comes down to tires, body, and motor.

On-road racing has really filtered down to three major types of car.  Pan cars, Touring cars, and Minis.

But first, lets cover the stuff all cars have.  Motors, ESCs, servos, and batteries..

Motors, ESC's, Servos and Batteries:

Motors are specified by the number of turns.  Physically, this is the number of times a wire gets wound around the motor.  More turns, means a slower motor.  The slowest common motor is a 25.5 turn motor.

ESCs (Electronic Speed Controllers) come in two varieties.  "Blinky" and everything else.  Blinky (this referers to a blinking light) indicates an ESC that doesn't change motor timing.  This is used for all controlled motor classes.  If a class has an open ESC, variable timing is allowed, and that class becomes "Mod" or "Modified" racing.  That term is a holdover from the old days, where there was "stock" and "mod" brushed motors.

Servos, are how you steer the front wheels.  They're available in roughly two sizes, and they're rated by some torque number, and a speed number.  Higher torque numbers are generally good.  The speed number is generally a measurement of how long the servo takes to move 60 deg.  The lower the number, the better.  Short servos are usually lighter than full size servos.  Really cheap servos have difficulty centering, so this is a place where spending some money is a good idea. 

Batteries, for most on-road racing come with four important distinctions.  Cell count, C rating, cell count, and voltage limits.  The number of cells is counted in "S."  On road racing is either 1s or 2s.   It's very rare to see 1s in anything but 1/12 scale cars.  C rating tells you (or tries to tell you) how fast you can draw power from a battery.  Generally the bigger the number, the better.  Finally there's two max voltages available.  HV and normal batteries.  Most LiPo batteries are limited to 4.2v per cell max.  HV cells can be charged to 4.35 volts per cell.

Chassis Types:

Ok, lets talk chassis.  We'll start with the simplest.

Pan cars, which include F1, World GT-R, Pro10, and 1/12 scale cars.  Are made of a flat pan of material, and a motor that directly drives the rear axle.  These classes are about 50/50 1cell racing, and 2 cell racing.

Touring cars, are cars with 4 wheel independent suspension, and generally 4wd.  There are some FWD and RWD touring cars, but they are uncommon these days.  They can be belt, or shaft drive, but that's a concern for later.

Mini's are a offshoot of Tamiya's Mini chassis.  There are now more manufacturers.  But they're shorter and narrower than the typical touring car, and allow the scale use of smaller cars.  Think Miata, instead of a Corvette.  Mini chassis can be 4wd, FWD or RWD.  Though the most common chassis are FWD.

Race Classes:

Classes of racing are usually specified by saying "Here's the style body", "here's the expected motor", "here's the expected chassis" and "here's the expected tire."  So here's a short list of the common classes.

We'll start with the catchall.

Sportsman:  Sportsman is typically a "run what you brung" class.  Show up, with car, and they'll put you on the track.  Generally, if you register for a serious racing class, you can't run sportsman.  This is where some people start.  It gets you track time.

Pan Car Classes:

1/12:  1/12 racing is almost exclusively 1S batteries, and tend to run very low turn motors.  The slow class for 1/12 racing is typically a 13.5 turn brushless motor.  Modified classes will run down to 2.5 or 3 turn.  They also run foam tires, and wedge type bodies.  1/12 racing is fast, precise, and waaaay up there in the skill tree.

World GT-R:  This is a 1/10 scale pan car.  Narrow chassis (200mm)  on rubber tires.  They run 1s batteries, and a 17.5 turn motor.  They're not fast, but they're very simple cars to run.  You're expected to run a sports car body in World GT-R.  Corvette, Ferrari, Porsche, etc..

LMP: This class is essentially 2s World GT-R.  Same rubber tires, but you run a LMP style body, a 25.5 motor, and a 2s battery.

F1: Formula 1 is a pan car, that looks a lot like a modern Forumla 1 car.  they are very narrow, 180mm, run rubber tires, use a 2S battery, and a 25.5 turn motor.  They look great running around the track.  This class is specified by USVTA

Touring Car Classes:

Touring car:  Touring car is going to be a narrow rubber tire.  2S batteries, and a 4 door sedan body.  Usually with a wing on the back.  The classes are further narrowed by motor and tires.  You'll see terms like "mod", "stock" and "spec" and "super stock".  Those typically define motor and tire combinations at a local track.  You will need to call to find out what those are.  Mod really means anything goes.

FWD Touring Car: There are some places running FWD touring car classes.  They're the same as 4wd classes. Just with front wheel drive.  They tend to be easier to drive, and a bit slower than the 4wd cars.

VTA:  Vintage TransAm.  This is a class defined by USVTA.  They're heavy at 1450g, they run a slow motor;  25.5 turn.  They run 2S, and a blinky ESC.  What makes the class unique, is you're expected to run a body from the first few years of TransAm racing, a spec vintage looking tire, and a driver figure.  Because it's the slowest, people are encouraged to start here.  It's also one of the most competitive classes in R/C.

USGT:  USGT is also administrated by USVTA.  The cars are lighter (1380g) than VTA, run a slightly faster motor, and you're allowed to run a GT car body.  So that ranges from exotics, like the Pagani, and the FordGT, to some pretty mundane cars, like a modern Mustang or Corvette.  USGT also has a rule for FWD cars.  FWD cars have no lower weight limit.

Euro Truck: It's roots come from Tamiya's national event series.  They sell a low end touring car chassis, with a semi truck body on it.  The class is "run the kit as provided".  There's typically a spec battery.  It's a fun class, and very evenly matched.  It's a little faster down the straight than VTA, but slower in the corners.  It's fun to watch, and drive.  So if you buy a Euro Truck kit, don't start buying upgrade parts, they're not allowed.

Most tracks also have their own house classes.  To find out about those, you need to contact the track.

Mini: Mini is also a Tamiya based class.  The cars are narrow, and short.  they typically have compact car bodies on them.  They're still usually 1/10 scale.  There's generally a 21.5 spec motor.  Otherwise the tamiya provided 27turn brushed motor is generally legal.  You'll need to check with your local track for tire, and non-tamiya chassis legality.

So now you know "what people race"  or more importantly, what you could race.  How do you race it?

Actually going racing:

You've got your car, you know what the local classes are, you've got a car that you want to go racing with.  Now you need to get there, and be ready to race, at least three times.

The facilities provided by the track can vary from "nice workbenches, with power and chairs, a pro-shop stocked with parts, and tiled indoor bathrooms" down to "well, there's parking, and a Port-o-let".  Unless you know the track, definitely call ahead to find out what the facilities will be like.  Always bring an extension cord.

When you call the track, you want to ask: How much is race entry?  Do we need to purchase transponders, or do you provide them?  Is there power, are there pit benches?  What time do I need to show up to register?  Is there practice time?

Bring spare parts.  While racing, steering knuckles and tie rods are common failures.  Also have a few spare of each type of fastener on your car.  You'd also not regret a spare pinion or two, and a spare spur gear. 

Your car, almost always, must be painted.  So paint your car. 

When you get to the track, find the race organizer.  Get your entry fee paid, and make sure they know you, the transponder situation is settled, and they know what class you'll be running in.

Next is to setup your pit.  Get your space cleared, get your tools out.  Get your charger setup.  Get your car ready, and go find out when you can hit the track.

Now, you're ready to race.  Almost.

Depending on the race, you may have to put your car through tech inspection.  Ask the organizers about that, when you register for the race.

The Race Itself

RC car tracks are not all that big.  And once you get more than say, 8 or 10 cars on a track, things star to get crowded.  To take care of this, we have qualification races, before a main race.  This also means you get to drive you car a bunch of times throughout a day of racing.

It's typical to have two, three or four rounds of qualification before the main race.  Often these qualification races will have the drivers re-sorted to make sure people of similar speeds are racing together.  Sometimes they won't... but hey, that's racing.

Qualifiers are often what's called an "IFMAR" start.  That is, you all line up at the beginning of the start/finish straight, and when your name is called, you start racing.  This intentionally spaces you out, and reduces the amount of carnage at the first corner.

Mains races are usually started from a standing grid.  Though rolling starts "are a thing" too.

"How to race" is an article for another time.

Friday, October 5, 2018

The next upgrade for the USGT FF03

I've had these parts sitting in my toolbox for ages.  The Tamiya parts, not the PJ Masks placemat...



Here's the steel pivot set:



The aluminum ones, with aluminum screws, weighs 1.5g.  Saving a full 2g. 

While we're at it, here's the stock top shaft. 



11.4 g, between the shaft, pin, gear, and o-ring. 


That's not a typo.  3.7 g for the replacement aluminum part.  A 7.7g savings.  

Finally, I swapped a whole lot of steel screws for aluminum.


Aluminum screws weigh half what steel screws do.  So another 6.5g there. 

16.2g came off the car last night.  Most of it high up in the chassis.  I can't say i'm happy with the amount of effort that took, but... It's what needed doing.  


Tuesday, September 25, 2018

Tamiya Ta07 - PSM carbon chassis

Oh, it's that time.  Time to make a TRF419 from my TA07. Or.. something like that.



When I heard PSM was releasing the carbon chassis, I was, more than intrigued.  That also sent me down the path of finding out if there were aluminum bulkheads available.  As it turns out, there are.  Eagle Racing makes them.


The process of switching from one chassis to the other, is really not so bad.  The hardest bit was re-threading the drive belt through the motor mount.



Out with the old... 

And in with the new.



The new bulkheads look very open, and really remove the distinguishing shapes of the TA07



They had to pull some interesting stunts to get the top deck to clear everywhere.  


The little bridge to clear the rear belt path too.


That would look so much better with aluminum suspension mounts.  But those are to spendy for me.


Other than the review of how it drives, that's really it.  The car... is now a pretty typical double deck touring car. 

As for how it drives?  A lot like the full stiff setup of the TA07.  Color me pleased.