Sunday, January 31, 2016

The Aluminum Xray...and a note on the Serpent wing

After some races with the Xray X1 on the new CRC black carpet, I was interested in possibilities of stiffening the car overall.  The X1 has shown it capabilities on various surfaces from asphalt to carpet. This versatility is great since the car will be competitive almost anywhere, but sometimes there are areas where specialized parts help.

Jan Rathiesky showed up at the first ETS race of the season -  on carpet- with the aluminum chassis on his Xray. (photo - RedRC)
This is probably a hint.

Anyway, what stood out to me after a couple of these events on the high traction CRC black carpet was that the new CRC F1 with the transverse battery looked awesome...and it was also very flat on the track.  It rarely seemed to pick up a tire or traction roll.  CRC's website does make mention of the high stiffness weave of their chassis.  The car also has a solid lower arm, which I assume is stiffer than the Xray lower arm.

In any event, I wondered if trying to remove some of the flex in the Xray car could help in high traction.  

I was able to get an Xray aluminum chassis as well as front lower arms by Xtreme Racing.  They sell a lower arm with additional bracing for some more stiffness.  I added both these parts to my car, keeping the setup close to see what, if any, difference could be found.  Note that the aluminum chassis is 2mm vs. 2.5, so the links and the "football" pivot need a 0.5mm shim to maintain the proper orientation to the stock pod plate.

At the track, I prepared the tires as I did with the original equipment.  Putting the car on the track, I noticed the car did not have quite as much mid corner steering as it had before, but it was very flat as it went around the track.  This was good as there was recently a well attended series race at the track on the same layout and traction remained very good, though not as high as the CRC black carpet.  I also felt like the car was smoother and more predictable all the way around the track.  I could drive in a more on power style as well, which I prefer.  Adding 0.5mm to the rear of the upper arm for a total of 2.5mm of dynamic caster spacing added the mid corner steering I wanted.  It seemed like the car held better corner speed, as I could roll down in throttle and the car didn't seem to bog or "stop" in the corner as it did occasionally before.

Overall, the car gained a more composed feel on carpet.  As good as the Xray car is, there have been times where getting the amount of steering into the car to be competitive could make it a little unpredictable.  During on of the races, a marshall commented on how good the car looked, and how easy to drive it looked as well.  It was really good for how little I had to change in setup.  In a couple weeks I'll be attending another race on the new CRC carpet so a real shake down will occur then.  I'm sure I'll have some more thoughts about the new chassis.

Serpent wing update:
I mounted the wing to the graphite tongue I made with aluminum screws.  PLEASE USE ALUMINUM SCREWS HERE!  I had a harsh crash in practice at full speed, and one screw sheared off.  Nothing else was damaged.  The aluminum screws are like a fuse that will pop off in a very bad accident and save the wing and/or the graphite parts on your car!  I also wound up using 5mm spacers to keep the wing off the track....

Sunday, January 17, 2016

Bulletproofing the Serpent wing

The new wings Serpent has come out with are great.  Adjustable, beautiful, and lightweight, there is only one problem: the front wing breaks easily at the attachment.

It appears the object was to keep the front wing lightweight at the attachment, and maintaining a realistic look.   Both were achieved, but a good crash will crack the wing.  I attempted to rebuild and re-enforce my broken wing with J-B Quick epoxy and a piece of carbon fiber, but it broke just as quick again on the next practice run.

At home, I thought about what could be done, and I realized that just the wing itself could be attached as the Xray lexan wings are.  I was able to remove the old wing pylon and drill the wing element for an Xray bumper.

At that point, I decided that while the Xray bumper certainly would be secure, it would probably be a bit heavy, and possibly strange looking.  I decided to use some scrap carbon fiber chassis material to make an attachment using the same hole pattern as the Xray bumper.  This would allow me to use either the Xray bumper or the carbon fiber.  Not a bad option if the carbon fiber did not pan out in testing.

It didn't take too long to make a little tongue to mount the wing to the chassis.  Not only is it light weight, but it allows some flexibility in how high the wing is mounted as well via spacers underneath the wing element.

I have 2 sets of holes to allow a little more forward mounting.  I did have to do a little dremel work on the wing where I made the mounting hole to remove some material so the wing would have the proper angle.  It initially wanted to tilt back slightly.  Taking a little off the wing bottom forward of the holes let the wing sit at te proper angle.

All in all, this worked out fantastically.  I ran it all day at the local series race, and there were no problems.  The wing proved very durable once the attachment was improved.  I noticed the lighter Serpent wing gives a little more steering and response, so the carbon fiber attachment only improves this aspect.  At some point I will try to make a better finished version, but this prototype piece worked in an excellent fashion. 

Sunday, January 3, 2016

F1 Flow Chart

I made this post over at RC tech, but I figured I'd copy it over here before it winds up pages back on the thread....

F1 Flow Chart:

TCS racing?
If yes, see below, If no skip directly to "Buy XRAY"

Do You race on carpet? If no skip directly to "Buy TRF102"

If yes, this is where things start getting interesting.

F104 t bar cars - you need to really look at the F104X1 (or a car optioned to the same spec) or the F104W GP. The X1 has fiberglass chassis parts which actually can be a good thing. It makes a little more traction and has a little more weight down low, which again is not all bad. I have witnessed several brutal beatdowns on high grip carpet with this car. Pretty well optioned if you can get a kit/car. Really the only things you may want are the carbon axle, and clamping hub.

The WGP car is very similar, however you will need to buy the standard F104 front end plastic parts and shorter turnbuckles as the car is an older "wide" 200mm car with the included F103 front end parts. That being said, it is the most well optioned F104 in my opinion. All pod parts are aluminum, chassis is graphite, it includes the aluminum front knuckles, and the t plate I like better. The t plate has a different flex point which I think makes a little more traction. You may also fit any of the other F104 t bars as well, noting that the standard F104 cars cannot use the WGP's tbar due to the larger chassis opening required. Last time I checked you can still find this car for under $200 USD at rc-art online from Japan.

These cars don't turn in quite as hard as a TRF102, which has a much thinner chassis and flexes more in general. That's not always a bad thing, but I have always found that you need to keep a good balance in the car's handling to make it driveable. The car will feel either a little dead off the center of the wheel or it will get a little unstable if you want a steering machine. This is not a concern if you are only racing other Tamiya cars but you will be off the pace vs. Xrays or cars with a similar layout. (off topic excursion coming...) In my experience, and that of even other guys who I feel are better drivers than I am, you won't get the ultimate pace of the other brand chassis. I have been to non TCS races where we threw the kitchen sink at it and in the end you just make the car hard to drive trying to keep up.

The TRF101 has some nice features, including the ability to move the links around and has a little more flexible chassis than the F104V2. Oddly enough, I always had the feeling that it accelerated much better than the other cars in the series, why I don't know. I haven't tried to measue the pod or anything to see if there is some difference, but whatever.

I really don't care for the front end. There is little adjustment and the design is less than optimal to use what should be good features. If you let the upper arm flex too much, the kingpins can pop out. Ride height can be hard to set where you want it. No caster adjustment, like the normal F104 front end ( well not really true since you get more caster the less camber you run). It actually would have been super simple to add to the design via a couple extra holes in the upper arm, but that's neither here nor there. It's simple, and camber is easy to adjust to the 2 positions offered, but on carpet you wind up searching for steering most of the time. At least the F104 front end lets you have 6 camber settings and the ability to add dynamic caster like a 1/12 car with different height ball studs. The more stable handling has seemed to work for some on asphalt. Trying a set of the normal F104 upper arm parts might make this car a little better, but I have always liked the feel of the t bar's more stable launch out of a corner vs Tamiya's link cars.

Getting to the TRF102, the biggest flaw is the chassis if you are going to race carpet. I have gotten this car to within a couple tenths of my Xray car on carpet, which is pretty good since I feel like the Tamiya front end does not produce the steering of the Xray. You need to strap the battery to the chassis and also use double sided tape to make the battery a "stressed member" to help stiffen the car up for carpet. Otherwise, every corner is an adventure if traction is up. For non TCS racing you could fashion an upper deck from scratch or cut up F104 parts, as the holes line up. This is semi effective, but you will get crushed by Xrays and their clones anyway. The other problem is that a lot of the steering is actually produced by chassis flex just behind the servo, so you can't just make it a tank.

I think the TRF102 is probably going to work out for carpet if you use the battery to get the car stiffer. It does have a good amount of steering that just needs to be tamed. Work still needs to be done to get it 100% dialed for carpet, in my opinion. Otherwise, I would go with an F104WGP, which just has a different feel, and can be really fast as well, and has a lot of good setup knowledge out there.