Team Associated B5M R/C race car

A customer of ours is a sponsored R/C racer, and over the course of a few visits he dropped off some toys for me to play with. They're both incomplete obsolete racers, but the newer one that came in a box is only JUST obsolete. It's a Team Associated B5M. I've decided it's time to make it functional. I also have a B3 or B4 (I forget) that's a roller. It may donate some parts.

Now, I haven't done much with R/C cars for years. Or ever, really. I built a Tamiya M2 Miata a couple of decades ago and proceeded to illustrate just how far over my head I was in driving it. So this much faster beast should be a much better choice!

Because I have no idea what I'm doing other than the basics, I am open to suggestions and information. I want to learn how to set this thing up and how to do what it can do, so this thread is half learn me and half build diary. The goal is just to make the car work, not take it racing. It'll be fun to build and fun to play with. It's no fun in a box.

So, here's what I've got. A classic racer's stash of spare parts but with some expensive bits missing. I have something like 4-5 transmission housings but only one set of transmission internals. Control arms out the wazoo. A spare chassis that's a bit different - it may be an older one. There are both "hard" and "soft" versions of things like control arms.

I've already done some assembly on the chassis so I have a better idea of what I'm looking at. Luckily, I also got the instruction manual that has part numbers so it'll be easy to order missing parts.

Chassis with the steering servo in place and a complete front suspension (minus one bolt).

Closeup on the servo.

One of the baggies of spare parts. The other includes rear uprights and a bunch of camber adjusters.

Motors and a speed control. There was something he told me about one of these motors, something like a different number of turns for different behavior. Part of tuning the power delivery? How do the turns work?

I've also got a controller that's mind-boggling. I forgot to take a picture, but it's got a screen with multiple configuration pages on things like traction control and ABS and probably some way to control the weather.

Missing are the rear halfshafts (easy enough), possibly some bits in the rear uprights, a receiver, a battery and a body. The older car may donate a body. I also need some shock oil to assemble the two shocks that are pulled apart.

Question: it's been strongly suggested that I get some LiPo batteries and a charger. What's the run time vs charge time look like on these? Do I need two batteries for goofing around fun time, or will the thing run long enough on one charge that I won't feel disappointed when it goes flat? Do I need a low voltage alarm on the batteries to protect them?

Get yourself a toddler to assemble it.

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/hybrid-rc-car-build-thread/78255/page1/

Too bad Photobucket ate the pictures.

Boo photobucket! I shall read and absorb, thanks.

I actually have a pair of little rock crawler cars that were purchased a year ago so my little 4 year old nephew and I could play around. He's developed frighteningly good control of them. But I think he's a little way from assembling. He did watch me rebuild one of the axles with fresh grease on Saturday, though, and that's what got me thinking about the B5M again. If you want a cheap RC crawler for a little kid, these have stood the test of time.

17.5 turns is 'stock' and fewer turns is 'modified' in the racing world. Modified are faster and generally cheaper as they don't need to fit a 'stock' rule where the motors are more highly tweaked to stay within the rules but provide real power.

Yes, you want LiPo batteries. I'm using a couple 4400 mAh shorty batteries. They are generally sized for the 5-7 minute race heat times, though I've easily run 10 minutes (though I'm not on the throttle as much as a good driver as that's how I end up upside down somewhere off the track.) You will also need a charger. They vary a lot in cost, but be sure it can handle a 2S (two cells in series) LiPo battery at about 7.5 volts nominal. Charge time depends on hard you push the charge. Generally for good battery life, you'd like to charge at 1C (4.4 amps for a 4400 mAh battery) though 1.5C doesn't seem to be a problem. So that gets you more like 20 minutes of charge time for 5-10 minutes of run time.

These things can't really be run continuously, though, especially with 17.5 turn motors as the motors get hot and need some time to cool down. I don't really have data, but I look for no more than 50% duty cycle (equal run and cool off times) when practicing, and I'm not sure that's really enough.

Specific to the B5M, there were two different sets of front and rear arms for the B5 models. The M (mid motor) used the gull wing fronts and slightly more rearward rears (longer wheelbase). The shock tower on the front is also specific to the type of arm. I don't really know how to tell the difference. There was a lot of part swapping going on in search of optimal setups, so you could easily end up with a mixture of parts. I just bring this up to be aware of the variables.

I thought 27 turns was stock?

Keep the other one in the box. Resist all urges to open it. Sit on it for 20 years. I've seen very early RC10T kits, the ones with the spare skinny front tires, still in the box, go for 4 figures.

Neither of these are pristine stock cars in boxes. The one in the box is in bits, and not complete - that's the B5M. The other is a rolling chassis with a history of racing. They are far from "in the box". I'll let someone else buy toys for the kids in 20 years

The grey motor in the picture says "9.5 turns" on the case. Would it run cooler than a 17.5?

According to the specs, this can take "saddle pack, shorty pack, or square pack" batteries. I'll do some looking around.

tuna55 wrote: I thought 27 turns was stock?

27 turns is stock for a brushed motor. 17.5 is stock for brushless.

To be honest, a 17.5 brushless is WAY faster than a 27 turn brushed.

Also, the brushless motors are all rebuildable and have bearings in them. The reliability is the same as a brushless mod motor (less than 17.5 turns).

With some adjustable timing and the right gearing, that thing will be every bit as fast as a brushed mod motor from just a few years ago.

Get a temp gun and keep the temps around 160 max (iirc) on the motor for longevity.

Can we get a picture of your transmitter? The receiver may be very specific.

decent hobby level set and forget charger

decent battery. the C rating is how fast it can be discharged without melting down....

Less turns runs hotter if I remember correctly. I'm pretty sure "turns" refers to the number of times the wire on the armature has been wrapped. Less turns = thicker wire which gives more power at the expense of run time and heat generation.

I was remembering 17.5 turn stock motors as running hotter, but now that I think about it, I think that's because people push the timing farther to eke out more power and that's more of a driver of temp. Keep the timing at 30 degrees or less, at least for a 17.5 turn motor, and it sounds like that should make temp not much of an issue.

Here's the transmitter - an Airtronix M11X.

That control panel. I have some learning to do. Luckily, I was able to find an online manual for it.

Yeah, I'm still trying to figure out everything the transmitters do. Fortunately online manuals are available for just about everything.

On that topic, there is a ton of info on the first page of this thread: http://www.rctech.net/forum/electric-off-road/780905-official-team-associated-rc10-b5m-mid-motor-thread.html Most of it is racing oriented, but there are a lot of good resources linked there.

Here are pics of our cars to give an idea of how the electronics can be installed. Not saying it's the best way, just the ways two different people built our cars.

Thanks for that link! Although - 1405 pages!

Spent some time on this today. First, here's the roller I also got. I'm not sure what generation it is, but I think it's a B4. I contemplated leaving it together - but figured that it'll just continue to collect dust, and using it as a parts car will be a lot more fun.

It's got some trick upgrades, like these aluminum/CF rear uprights. And there are the halfshafts I need!

So I tore it down...and discovered that everything is different. Even the fasteners on the B4 are SAE and the B5M has metric. Seriously! Everything's also bigger and burlier on the B5M. In order to use those rear uprights, I'd have to add spacers. And drill out the upright for a larger pivot. The width of the arm where it attaches to the chassis is the same, so I pulled apart the rear end of the B4 and...no. Again, a larger pin and I'd prefer not to take any more material out of these than I have to.

B4 on top, B5M on the bottom.

So it looks as if the parts car isn't going to be any help at all. Even the wheels are different. I've put together a shopping list and I'll start pricing out all the little oddball parts that were scavenged from B5M before it was passed on to me. I'm starting to realize it's like someone gave me a trailer with an F1 car inside and I'm trying to turn it into a track car.

I do have a choice of two spur gears for the final drive. The small one is for "stock" motors, the bigger one is for...well, non-stock I guess. Depends on if I need torque or speed. I'm thinking speed Now I just have to come up with the right pinion gear for my shopping cart.

So, how do I select a pinion gear? I know how gearing works. But can I mix and match any spur/pinion combo as long as the pitch is the same? I'm assuming there's some adjustment in the motor placement that allows me to fine-tune the mesh. I can't check that right now because I can't assemble my car far enough.

Keith Tanner wrote: So, how do I select a pinion gear? I know how gearing works. But can I mix and match any spur/pinion combo as long as the pitch is the same? I'm assuming there's some adjustment in the motor placement that allows me to fine-tune the mesh. I can't check that right now because I can't assemble my car far enough.

Correct. However, There is a limit to how far you can go.

I would check to see what the factory runs in their rtr kits for this chassis and get that gearing. I would also get a couple of pinions larger than the stock geari g.

With the 17.5 motor we are running a 30 tooth pinion with 72 tooth spur. With the 8.5 turn motor, the pinion was 20 tooth, but I haven't had the clutch off to look at that spur. That seems to indicate that the modified motor runs a lot faster than the 17.5 motor. I can confirm that now that we have switched out the modified motor for the 17.5 motor, that car is now a lot slower than the other one. We're now waiting on parts to go 30/72 like the other car.

Regarding B4 to B5 differences, it's my understanding that the B5 is Team Associated's first metric hardware car. The rest of the industry is metric, so Associated is now, too.

Just placed a massive order with AMain (mostly) and a few other shops. Thanks for the suggestions on what to look for on things like batteries, etc.

I should have everything by the end of the week and my wife is out of town this weekend, so I've got a full weekend of fun electronical projects ahead of me. I'm sure I'll hit some sort of snag but that remains to be seen.

Well, the snag has been hit.

First, it looks like the fully assembled transmission that came with the car is a low-friction "three gear" design that is basically flipped compared to the four gear setup. This means the covers for the gears that I have don't fit, so I have to order one of those. Also, I somehow overlooked the fact that I'm missing a bunch more parts for the rear uprights. So, another (much less expensive) order in to AMain and we wait again.

I did take some time to build some rear shocks. I had to scavenge some parts from the B4, finding probably the only parts that are common between the two chassis. Bled the shocks and they're good to go.

Now, the big snag. I picked up a receiver that's compatible with my radio, it's a cute little thing.

And I can't plug in any of my connectors. They're SO close, but not quite. Looks like there's partial standardization but not complete. You'd think "uses X connector" would be in the technical information. Looks like I might just have to shave down the connectors and maybe move some pins around.

Question - what channels are traditionally used for what electronics? Channel 1 for steering, channel 2 for throttle, etc?

This is where I am right now. Once I figure out the wiring and do a bit of soldering, I'll be able to make some noise at least.

Based on what I know about associated, that roller is a b4. The tubs were the same as the t4 of the era, and God knows I've built a few of those.

Question!

My battery came with a pigtail that includes this little connector. The middle leg goes into a separate port on the battery, the outers are + and -.

What is it for? To power the receiver? Or something else?

Keith Tanner wrote: Question! My battery came with a pigtail that includes this little connector. The middle leg goes into a separate port on the battery, the outers are + and -. What is it for? To power the receiver? Or something else?

The little white one is a pinout for your cells. Each lead connects to a board that you'll get woth your charger. That board tells the charger whether or not the battery is safe. If a lipo charger detects an anomaly in the battery, it won't send it any current.

Thanks. I just found one on the lipo that was inside the transmitter as well, so I was starting to think it had to do with charging. I didn't get the magic board with my battery, so I'll pick one up. What's the name of that connector?

I am learning that the game of RC cars is one of incompatible connectors all around. But I feel like I'm getting on top of things.

Is the receiver power usually tapped straight off the battery, unswitched?

Looks like my new charger (Dynamite 4060, suggested earlier in this thread) doesn't do battery balancing. It's too late to return it for full credit, but looking at the adapters I'll need just to hook up to my batteries it's less expensive to buy a new charger and take the hit on returning the Dynamite instead of buying a balancing doohickey to go in between.

One more thing.

Keith Tanner wrote: Looks like my new charger (Dynamite 4060, suggested earlier in this thread) doesn't do battery balancing. It's too late to return it for full credit, but looking at the adapters I'll need just to hook up to my batteries it's less expensive to buy a new charger and take the hit on returning the Dynamite instead of buying a balancing doohickey to go in between. One more thing.

You are not racing. Even if you were, you don't need to balance.

I have made plenty of A and b mains at plenty of big national roadcourse races and have never once balanced the cells in any of my batteries.

Just keep that charger and use it. You will be fine.

For the receiver, check to make sure the wires are in the correct order on the plug. If they are, you can either shave the plug down to fit, or depin the plug and get a new plug at a decent hobby shop and repin the new plug.

Keith Tanner wrote: Looks like my new charger (Dynamite 4060, suggested earlier in this thread) doesn't do battery balancing. It's too late to return it for full credit, but looking at the adapters I'll need just to hook up to my batteries it's less expensive to buy a new charger and take the hit on returning the Dynamite instead of buying a balancing doohickey to go in between. One more thing.

Oh yea, for charger connectors, we always just ran alligator clips. They will work with almost any battery.