John Stranahan

iTrader: (27)

The roll centers on the TC5 are indeed very adjustable from well below the ground on up. It is not that desirable to put the roll center below the ground. When you do this, part of your cornering force is used to jack the suspension downward as cornering force acts on the roll center. The roll center is good at the ground. Occasionally on asphalt the surface becomes very high grip. This happens toward the end of day 1 of a long race. It is helpful then to reduce grip a little. You can do this and at the same time add stability by adding sway bars. You can do additional good by raising the roll center a little. You can also use roll center to fine tune the car by making small changes to the roll center, when moving a coil over shock to a different hole is too much change.
Diagram the instant center (big dot) is located with lines along the suspension arms. A line from the tire to the instant center crosses the center line at the roll center (big arrow). Low roll center (soft supple, grippy). High roll center (slides, stiff, responsive)
The excell spreadsheet is accurate for the TC5. I set my roll centers to near zero with it.
The instant centers do swap sides of the wheel when going from off-road truck say to an onroad Touring Car. The instructions to draw the basic diagram are the same. It matters not which side of the wheel the instant centers are on.

Redwood

Thanks John, great answer, I have come expect nothing less!

Thanks

Neal

John Stranahan

iTrader: (27)

Neal-You are welcome. Good luck!

Xray-T2 ECD axle install continued

I have a part number now for an inexpensive bearing in 5x10x3 four pack at Boca Bearings. It looks like this will simplify the T2 axle install by allowing all TC5 plastic parts. The oudrive hole will still have to be opened up. I ran a short test and the axles seemed to work fine. A longer test to come. We have new asphalt now and are awaiting a MR105N-2gs/W3 green rubber seal

John Stranahan

iTrader: (27)

Cooling the Motor

I was asked about this by Private Message. I thought I would respond now in more detail. Last year I was only running with the Nitros. Races were five minutes. This year we will have an open mod ROAR rules TC class. Races will be 6 minutes and at a rather porkerly 53 ounces. I added 5 ounces of ballast to my TC5. Previously I had cut two extra slots on the motor side in front of the motor shaped liked the battery cutouts on the other side. This allowed air from under the chassis to impinge on the motor can. You could tell by dust and rubber deposits that there was a strong fast stream there.

This year I have to run another minute sometimes with 140 F track temperature. Here are my solutions.

First I found that a front diffuser directs a lot of air above the chassis. This is retained. It actually helps cool the motor and speed control.

I enlarged the rear of my new chassis slots to pull more air.

I use an LRP TC edition speed control which runs cool under these harsh conditions. I think the active timing is responsible.

I am using the latest Novak Ballistic 3.5. The dyno sheet looks like it will run the coolest of the 3.5's available. It has more bottom end punch and will require less throttle most places on the layout

I installed a dual fan harness. At the moment I have a very strong fan from the LRP Sphere Comp TC edition speed control in front of the motor.

I removed the motor trim ring to get right at the stack with air. I soldered the wires to expose a bit of the tabs to air. This will cool the wire coils directly.

We have huge traction right now. This creates more speed and more heat. You will need to roll on the throttle smoothly to keep from having that 200 amp inrush current at full throttle except where absolutely necessary. In other words save full throttle for higher speeds.

I have left plenty of space in front of and behind the motor for radiative type of cooling. This is the most effective cooling as the motor gets hot. Heat is radiated directly into the space. If it hits a surface it will be absorbed and partially radiated back.

Lastly be cautious with too much motor cooling. What you might achieve is a cool outer surface and a very hot inner wire coil that shorts and fries the motor. Been there. I had a very effective liquid on fabric cooling sleeve on the motor, but I fried one tinkering with it.

On order. Twin fans and duct for the TC4. This may or may not be better than the single fan I have. This would draw air from under the chassis through my slots and then blow it at the front of the motor. I think I have cleared enough space. Then a slight re balance will be needed.

Conrad

iTrader: (3)

Following your ECS posts with interest John as its something i was considering doing to my project car (Schumacher mi2). I was going to 'borrow' my mates T2 and see how the stock parts fitted before ordering the expensive parts.

Could you post sizes of the driveshafts so i could compare with my Mi2 shafts. I know you're a big fan of the Losi LCD, how do they compare in size with the tc5/xray driveshafts, any chance of using them instead as i know you can fit them to a cylcone if you use some of the jrxs parts [click]

On a side note, you converted one of your pan cars to run with multi link rear suspension didnt you? Or am i imagining things again could you point me in the correct direction please as i can find it with the search. Thanks!

John Stranahan

iTrader: (27)

Conrad- Nice link. The size axle I used is a 52 mm. This is the measure from end to end of the inner bone. It fit the TC5 Well. On the TC5 the best conversion is going to be using metric 5x10x3 wheel bearings instead of Associated 6x10x3 bearings. Then all associated parts will be used, but the inner drive cup must be enlarged by .010 inch per wall or .020 inch in diamter. I have bearings on the way.

http://www.amainhobbies.com/product_info.php/products_id/34181/n/XRAY-Equalized-Cornering-Speed-ECS-Hudy-Spring-Steel%99-Drive-Shaft-52mm

The Losi axle may have an even larger inner ball than associated or Hudy. I asked about the dogbone length up above (a guy used them on the TC5) but he did not reply. I do know the outer axle are SAE threads and not metric. This makes you use the Losi c-hubs and steering blocks to have the least trouble.

Here is a link to the Home made 3 link rear suspension wide pancar with new double a-arm coil over shock front end. It is a really nice looking car. This is about the 5 th generation of the front end. The third generation of the 3-link rear end. Extremely fast on our new asphalt.

http://www.rctech.net/forum/5902189-post882.html

John Stranahan

iTrader: (27)

X-ray T2 ECD front drive axle conversion

I got in the 5 x 10 x 3 mm wheel bearings. I received the Boca bearings without seals at all for a part number described with green rubber seals. This is the first error for me from this company which I have used a lot. The new bearings allowed a little more streamlined and less expensive conversion as you can use the Associated hubs and C-hubs. The conversion goes like this.

Take the C-hub of your choice (caster choice) and enlarge the driveshaft hole with the small drum sander on the Dremmel. Bevel the outboard sides of the hole a little for additional clearance in the turns. The X-ray ECD's are nice and narrow where they pass through the C-hub so material removal is not excessive. You will not want to remove enough material to allow axle removal without disassembly like you have on the X-ray.

Use a tiny flap sander to enlarge your outdrive cups until the dogbone just slides in and out smoothly (photo in a post above). Trim the ends of the cross shaft in the bone to fit inside of the aluminum drive cup support cylinder if your car is equipped with one.

I ran a pack on the axles now. They worked well. No unusual wear to the Delrin cups. I stuffed the car twice without breakage of any front end parts. I think it's a go.

When I assembled the axles they were tight. They did not loosen up. This may happen partially from tightening the set screw which expand the little cylindrical bushing. I took my little flap wheel with fine sandpaper (600 grit) and turned it slowly in a drill to open up the dogbone hole that accepts the cylindrical bushing. You must use loctite on the set screws, but you can't let any escape to other parts of the drive axle. Dry the outer part of the setscrew before inserting it with the cylinder into position. I removed some errant loctite with the back of the X-acto knife. Smooth as butter now.

John Stranahan

iTrader: (27)

Diggety Design Battery Brace
With added cooling apparatus, I needed to rebalance the car. I had to take 1.2 ounces out of the ballast weight. I needed to move the battery a little bit right to offset the extra weight on the left. The Diggety design battery brace for the SMC battery that has a .060 offset to the right proved ideal. Here is a pic. The outer edge is wide of the chassis a little. I still am going to use a couple of battery tape straps to absolutely prevent ejection of the Lipo battery.

Side to side weights are now perfect again. Corner weights are good. My rear is a little light. (front to back is 50-50 but I prefer a couple extra ounces in the back. I have made some adjustments to compensate. If they work out I will post a report.

Also find a pic of the finished X-ray T2 ECD axle install

John Stranahan

iTrader: (27)

Bearing Conversion
This tool requires a lathe and tool post grinder. It is a stepped counter bore. It will convert the bearing recess in the TC5 steering block (knuckle) from 3mm wide to a 4mm wide bearing. The advantage is the 4 mm bearing is used on a couple of RC cars. The one in the Photo is a Traxxas DTXC 1535, 6 x 5 x 4 mm From Tower Hobbies. The width was not specified so I ordered some in case they were 3 mm wide. A second car that uses this 4mm wide bearing is the Associated Monster GT. The bearing will have bigger balls and be a little stronger in the 4 mm width. I have had few problems though with the Associated TC5 bearing which is the narrow width.

I started with a .500 inch old drill. The money step is the 4 mm wide by 10mm OD step. You have to be oversize about .002 on diameter and .015 inch on length for the springy plastic to cut to the correct diameter and depth. That would be .3957 on diameter and .172 on length. The pilot fits the inner Associated bearing seat and a .475 cut on the big end fits the counterbore on the inboard side of the knuckle. I made slight cutting edges with the Dremmel cutoff wheel.

Note the Boca bearing (YCWK105-YUU NB2 four pack) I posted above requires no modifications. It is a 10 x 5 x 3 with ultra seals or get a
MR105N-2gs/W3 with green rubber seals this is an individual bearing 10 x 5 x 3 mm.

John Stranahan

iTrader: (27)

I corrected the Boca Bearing number up above so that a seal will be included. Either an Ultra Seal (low friction low or non contact) or a Green rubber seal for good protection against dust entry.

Track Test, Cooling Test
Airtemp 96F Track temp 143 F (ouch)
I have run the TC5 a couple of times on the layout outlined with chalk and crayon. I had one run go 5 minutes. Motor temp was only 156 F. The cooling is working well. I have had to shrink my wing a little to roar specs. I am having some aerodynamic imbalance entering the sweeper now. I am loosing the tail. I will have to reduce front aero grip a little. I may shrink my diffuser some. Adding chassis rake with the suspension to lift that wing up does not seem to help much. You measure wing height with the car supported on a 20 mm board (3/4 inch plywood is about right) so this does not violate wing height rules. It is still even with the cab roof on the board.

John Stranahan

iTrader: (27)

TC4 Cooling Kit install
I received my kit. It consists of two fans that are wired together into a single plug. My pitch test shows that these fans are about as powerful as the ones on the Sphere Comp LRP TC Edition Speed control. That is the most powerful fan I had found previously. We should get about twice the air from the TC4 unit.

I decided not to install the duct as it is only half height and the motor is really hanging out in space quite a bit. I centered the twin fan on the motor can and mounted it with a #2 x 56 flat head screw about .25 inch long. I drilled one hole for one of the pins to help prevent rotation. As you can see my chassis is quite worn and the screw is small, so I glued the mount in as well. The fans are removable with screws. I think this should do it.

Note I also rebalanced the car to have 2 ounce excess in the back, body off. The speed control is back and down, I moved ballast back and to the right side. I am at 53 ounces. side to side weight is very good and even. Corner weights are perfect. See earlier in the thread how to check these.

I am going to try to run at 5 mm ride height as the new asphalt is smooth. To regain some suppleness (to remove some roll stiffness) I removed the sway bars. I increased my rear wing while keeping it legal size and legal height to improve entry into the sweeper. It looks more like a rear spoiler now, but it still has a narrow lip on the bottom to make it a wing. It is likely to be 98F for a test today.

John Stranahan

iTrader: (27)

Track Test
Air temp 93F Track Temp 132 (spotty clouds).

Wing, Roar Legal
You may not need this much wing unless you are on a very high speed layout. We enter the sweeper at about 50 mph.
I have made good progress. I am happy with the wings performance. It is roar legal and meets the following specs. With the car on a 20 mm board (3/4 inch plywood). The top of the wing is no higher than the cab roof. Place a spare chassis or flat object measure at the cab roof (150 mm minimum, this is where mine is now) measure at the back of the wing near the wing, you should get your cab roof measurement, in my case 150 mm. The wing chord should be 40 mm or less. A chord is a straight line. Measure from leading edge to the top of the wing with a flat ruler. You should be at 40 mm or less. Side dams should be 20-40 mm maximum. OK this is a little like doing your income tax. Now how to get the maximum effective wing while following the rules. I want a wing from cab roof to deck lid. This limits the shape to the one pictured. I used a maximum width wing no wider than the body. I cut down the side dams to 20-40 mm. I rotate the wing to just the proper angle to meet hight requirements and have it touch the deck lid and protrude out back no more than 10 mm from the top of the rear deck lid.

I like to save material behind the rear wheel cutouts which acts just like a side dam. I have enough material there to equal the side dams. I am getting good entry into the sweeper now. I have just a bit of wander still. I may be able to tune this out with less camber or a tighter servo saver setting.

Chassis Setup
Handling was good now at 5 mm but without the sway bars. The car is more supple and in control than before when it was stiffer.

Motor Cooling
I made a 12 minute run today. 2 minutes followed by one Marshalling and then 10 straight minutes. At the end, I climbed down to track level and gave the car four more good full throttle runs to heat things back up and get a more instant temp reading. Max motor temp was 178 F. This dropped quickly to 158F with only a minute of idling and running the fans in the pits. I think I have a go here. It should do 6 minutes. The track was at 132F today. There was a strong stream of hot air coming out below the motor when I picked the car up. I will have more traction on race day, but will be running fewer minutes.

This is a butt ugly wing setup, but it is very effective. I need a new body without the wing pylons.

John Stranahan

iTrader: (27)

ROAR wing rules
It turns out you have to look in more than one place to find all the wing rules. It must be 1/4 inch off the rear deck. The wing I pictured above would need to be raised up 1/4 inch and then trimmed on top by 1/4 inch or rotated more. Effectiveness would still be good. The DNA body has a built in spoiler that would catch any air going under the wing.

New Paint for the TC5
Pictured is the Hotbodies Dodge Stratus prepainted body. A couple were available for $28 at Stormer. I saw it elsewhere for $38 which is more typical for prepainted bodies. I put big numbers on it in case another racer has the same paint. I like the fit of the body on the TC5 very much. The hood and rear fenders have bulges for good tire clearance on bump.

Track test
93F Track temp 132 F
I had three good packs on the TC5 yesterday. The new track surface is now stripped. See the second pic.

Handling the Heat
The triple fans did there job well. I ran the car with decent traction for 6:20 seconds plus four hot passes after I climbed down from the drivers stand. Temp was 183 F. There is a little cushion left to 190F. I am using a Novak Ballistic 3.5 geared 90/20 x 2 for a 9.0 overall ratio. The dyno graph bears out the actual motor performance. Very good bottom end and midrange power.

Tires in the heat.
At 4:38 the tires lost forward traction on the infield. It helped to roll on the throttle a little slower. I used to just run the car a little loose for the next 30 seconds to finish. Now we have another minute added on and run 6:00 minutes. Some CS 36s should cure this problem. Some RP 40's did as well, but traction was a little less than desired.

John Stranahan

iTrader: (27)

Novak Eats LRP

When you have to blow out the fire in your TC, it was not a good day for TC. Recently you have seen pictures of my TC5 with the New LRP SXX TC edition and the Novak Ballistic series 3.5 (without trim ring). The LRP Sphere Comp TC edition previous to this was so good that I never had a heat related failure, so good, that I have 3 installed in fast cars and 1 (new in a box) of the old controllers.
It gets hot here in Houston. Air temp today was 101 F. Track temp was 146 F in between some light clouds. I had regeared the Novak Ballistic 3.5 one tooth less on the pinion (90/19 x 2) from test data on a very hot Friday. The motor was never over 183 F but it was being fan cooled. The core is hotter. I never measured over 140 F on the speed control. After the very first pass down the straight the car stalled. As I walked toward it a thick white cloud came out of it and was about 4-5 ft high when I reached the car. I picked it up. Yes there were bright red flames coming out of the terminal side of the speed control. Deja Vu. Now in my experience if you install a second speed control of the same model in the same severe service, you will see those flames again in Houston. I will have to use the repair in a lighter duty car. I was so pleased by the previous LRP speed control.

I suspect the speed control started to go south in my previous session on Friday. Maybe my part throttle weakness after 4 minutes was not tires and was this speed control thinking about letting out the smoke that makes all electronics function.
This new speed control has smaller dimensions than the old. This tighter packing of components is probably responsible for the failure, but it may be a one of kind type of thing.

The body with stock wing was surprisingly good until the fire.

yodace

iTrader: (8)

Need some hlp with the rear of my TC5r... the rear is loose when i enter and exit a turn...currently I am using rp36, i also took the washers out on the upper deck, front i have silver springs and the rear i have green.everything is nearly stock location wise.......asphalt track temp was around 150.......