Advice on CAT XLS assembly tips and brushed motor question

[McAnic]

Hi everyone,

I have a CAT XLS re release and haven't built it yet but have a question about the assembly and motor.

I've been reading up on various builds but was wondering if anyone here has some assembly tips for me? Like what to pay attention to the most or be careful of? What was the most challenging part when you built it?

I don't have any experience with the original and only have built a few Kyosho cars so I'm not sure what I'm in for.

My other question is about the motor/PRO transmission upgrade and alloy eccentric. If I use a brushed motor (paired with a 7.2v 5000mAh NiMH), maybe a 16T single, will I need to upgrade the stock transmission and alloy eccentric? I believe there was only a note on 17.5T brushless. How much "brushed" motor power can the stock transmission and spur gear handle?

Thank you!

[XLR8]

First post, welcome aboard.

The Pro transmission is a great upgrade, that's for sure.
A lot depends on track conditions and driving style but, for what it's worth, I ran variety of 10 and 12t single and multi brushed motors on 7 cell (8.4v) bitd and I didn't experience any reliability problems with the kit transmission. I think you will be fine with 16t on 7.2v.
.... that said, the Pro transmission upgrade is sweet!!

[McAnic]

First post, welcome aboard.

The Pro transmission is a great upgrade, that's for sure.
A lot depends on track conditions and driving style but, for what it's worth, I ran variety of 10 and 12t single and multi brushed motors on 7 cell (8.4v) bitd and I didn't experience any reliability problems with the kit transmission. I think you will be fine with 16t on 7.2v.
.... that said, the Pro transmission upgrade is sweet!!

Thanks, XLR8!

I guess I'll try the motors then when I build it. I'm torn with getting the Pro transmission just because it might be overkill.

[Dadio]

A 16t brushed will be fine , the upgrade transmition removes the integrator to just leave a standard front/rear diff arrangement , so you lose one of the most interesting features of the stock transmission , in my mind that's a downgrade not an upgrade .

[XLR8]

Interesting perhaps but I always struggled with the CAT's integrator. Running the integrator adds one additional ball differential between the motor and tires overall and potentially a total of three ball differentials between the motor and front tires. In order to prevent the three differentials slipping with a hot motor on a high bite track, they needed to be adjusted very tight which created a lot of resistance and potentially eliminating differential action making the car handle like it was equipped with spools (very loose in the turns).

With the integrator or with the pro diff assembly, in a turn the front drive belt runs at the median speed derived from the speed of the inner and outer wheels (the pro diff pulley is simply a very wide integrator pulley and the integrator pulley is the same diameter as the adjacent side pulleys). With the pro diff, there is direct positive drive to both front and rear diffs - nothing between the motor and diffs to add resistance or to slip*.

From my experience, I failed to find any advantage to running an integrator. Since the CAT was originally equipped with a spool and one-way bearings in the front, perhaps the integrator was meant to provide some advantage? The original car's front spool pulley was smaller than the integrator pulley providing some overdrive to the front wheels. What benefit does the integrator provide when combined with a front diff?

*EDIT: The Pro Diff does include a slipper clutch.

[McAnic]

Oh no! Lol. I'm confused now whether I should get the pro transmission or not. Thanks both for the explanation but it's a 50/50 and I have no experience with this car.

[Dadio]

I guess if you have the car already you could build it and run it and make your own mind up if you want to buy the upgrade transmission , the down side being that its a lot of work to retrofit .

[McAnic]

Yeah that’s what I was thinking, the retrofit part. If it it were a simpler kit I wouldn’t mind.

[XLR8]

Sorry , I never meant to confuse.

I never ran my CATs with anything as mild as a 16t motor on 7.2 volts as you are planning to do. Like Dadio says, you will be fine with the kit transmission.
However if you ever move up to a hot motor and 8.4v, you might also consider going with the pro diff.
Every RC car I've ever ran has at some point needed to be disassembled for maintenance or for an upgrade. It's just part of the fun.

[McAnic]

No problem at all! Appreciate every bit of info. Might be a good idea to just get a pro transmission, install stock, and later when or if I’ve gotten a lot of use out of it to reinstall the pro. I think I wouldn’t have bothered much but because I couldn’t find (or maybe missed it) proper info on max turn recommended brushed motor. Then reading up on people melting spur gear parts, etc.—but looks like that was from very loose slipper clutch nuts.

[XLR8]

No problem at all! Appreciate every bit of info. Might be a good idea to just get a pro transmission, install stock, and later when or if I’ve gotten a lot of use out of it to reinstall the pro. I think I wouldn’t have bothered much but because I couldn’t find (or maybe missed it) proper info on max turn recommended brushed motor. Then reading up on people melting spur gear parts, etc.—but looks like that was from very loose slipper clutch nuts.

That could be right. The basic CAT (or "kit" CAT - sorry ) doesn't include a "slipper clutch", it has a ball differential on the spur gear shaft - sorta like the original RC10's diff in the 6-gear trans. If a ball diff is allowed to slip, the resulting heat can melt the gear. This is true for all ball diffs - they are comprised of hardened steel ball bearings running on hardened metal rings (or plates) and they can easily become damaged if allowed to slip even for a short time. The Pro diff replaces the ball diff on the spur gear shaft with a proper slipper clutch.

As for assembly tips, honestly it has been a couple years since I built the Masami XLS re-re and I don't recall any difficulties or if the assembly manual contained errors. I can promise you that it doesn't go together like a Kyosho - it's an entirely different animal (there I go again ). I think if you study it closely as it goes together, you will begin to appreciate the genius of the design. It's a real race car and it's very durable as well. I raced the SWB and XLS often bitd and I don't recall ever breaking a single part.

[McAnic]

Thanks for the additional info! Looking forward to working on it (and running it) and the idea that most kits after that build will be quite easier.

[bismuth]

Hi,
The integrator is what makes this car unique. It is the perfect example of overengineering and the car is easier to setup and run without.
But this setup is part of its british charm. I think it will resist a brushed 16T, I plan to run mine with one too.
Pay attention to diff and integrator washer surface, they need to grip on the balls, so sanding them on a flat surface like glass with grit 600 paper in figure 8 and using the good silicone grease is mandatory. I don't know why this is left out from the documentation. The shiny surface of stock new washers do not offer enough traction to the balls and too much tightening force is then needed to prevent slipping, resulting in a too stiff integrator/diff action. Overtightening a brand new diff can mark the washer, It is better to tighten integrator and diff very gently first, then run the car without wheels with the motor around 2Volt to break in, then tighten normally. All this steps are important otherwise integrator's own stiffness added to rear diff one will make the rear wheels differential action very poor. Rear diff must be set up with integrator loose, finding the limit by rotating the spur by hand, when set, then integrator is tightened just enough to prevent slip, it's an act of balance. You will quickly learn to distinguish between a slipping diff and a slipping belt by its feel/noise. Aligning chassis and front diff to have belt correctly centered is tricky without adjustement screws. This car deserve its reputation of being hard to tune correctly.

[McAnic]

bismuth, thanks for the advice! That's interesting you mention sanding the diff integrator washers. I was just watching a video titled Schumacher Speed Secrets Video 1989 Schumacher Cat XLS from 1989 and the chief development engineer talks about this. I'm assuming the tech is the same and it applies. Are you keeping your transmission stock? And what pinion gear are you planning for the 16T motor? Thanks.

[bismuth]

Are you keeping your transmission stock? And what pinion gear are you planning for the 16T motor? Thanks.

Hi,
Yes stock transmission for now, maybe pro transmission if I install a BL motor later on and then reuse the stock transmission to rebuild the SWB version I'm now looking parts for.
My pinions/diff gears are from original SWB Cat in 32dp, I think I'll try 15/58 teeth to start with, for an overall ratio around 9, but that just guess for now, maybe others will have real recommendation based on experience. I think the equivalent in rerelease will be with a 23/89 pinion/spur.