Mabuchi540

I've been downloading manuals of various buggys and from what I've found so far it appears as if only the Kyosho Ultima Revolution comes as a kit, and has the ability to take any brand spur gear (the spur bolts to the outside of the slipper clutch plate, rather than being between the plates).

The Duratrax has this feature to but comes pre-assembled so that's a no go.

The questions are:

Is there any other top quality kit where the spur gear bolts on as mentioned above?

If not, does anyone make an adaptor so generic spurs can be bolted to either a XXX BK2/CR or RC10 B4?

Thanks in advance.

Davidka

iTrader: (86)

Get the losi or associated car. There are no features that could make the Ultima RB or the Duratrax as good at the B4 or Bk2. Spur gears for both cost $3-$4 and they last longer than the rest of the car.

Mabuchi540

True, but as standard they don't give a large enough range of gearing options (spurs) for stock racing. Stock racing here in NZ is limited to 540 Mabuchis and has been since I first raced off-road back in 1985.

Also the new track I'll be running on is big enough to run gas buggies on so gearing would need to be rather drastic and the B4 and Bk don't seem to have the space in the motor bay or spur sizes available to get where I want.

Unless of course as first asked there is an after market spur adaptor?

To give you an idea, when I last raced an old RC10 the gearing that most used on an electric only track was 6:1 or less (final ratio). On a B4 with a 78 spur to get the same sort of gearing I'd need a 33 pinion I think and from what I've seen there isn't the space.

If I'm wrong about that I'll happily stand corrected .

dirtracer1

well......you can either get a losi.....or a losi.

Valentin.H

iTrader: (117)

if you get a losi. minus well go pick up a xxx-cr when they arrive at your lhs instead of buying a bk2. or you could just buy a bk2 since there is a storm of them flying out for sale since everyone wants a xxx-cr

CaseyP

iTrader: (5)

If you glue the slipper pads to the gear and use a bearing in the center of the gear (used as the adaptor) you can use those kind of gears.

Scrubb

the b4 topshaft still use the standard mounting as the old single disk slipper clutch parts, just retrofit the old slipper parts on.

Mabuchi540

Cheers.

Scrubb

the slipper hub (the side the spur gear bolts to) from the original stealth transmission or a B2/T2 will retrofit right onto the standard B4 slipper hub with the original's slipper pad, or one from a current Losi kit, then you just need to figure out the spacing and thrust/spring assembly for the slipper.

with a stock 540 sealed silver can motor, i would put a bearing in a standard spur to keep the alignment of the gear, slide it onto the top shaft and bolt it directly to the B4's inner slipper clutch hub and run without a slipper. see photo.

Manning

iTrader: (3)

Just out of curiosity I tried a gear combo on my B4......

It currently has a 81 tooth spur, and the biggest pinion I have is a 25 tooth. There is not quite a 1/16th inch gap between the gears when installed and the motor is all the way back. So there is pleny of room for a much larger pinion.

The 78t spur measures 1/16th inch smaller than the 81, so that gains another .030".

Looks to me like the 78/33 combo is possible.

oople

I ran my wifes b4 with 78t and 28 or 29 pinion (biggest I have, dont remember which). and there was certainly room for more teeth on the pinion.

I used the 78t spur so I could put bigger pinions on.

Mabuchi540

so the hub in the picture is what comes with the B4 now (and with the addition of a bearing) and I should just bolt on a spur and do away with the slipper altogether using a 540?

Silly question, but I assume there are two mounting holes in that hub?

Thanks in advance.

Scrubb

yes the standard slipper plate with two holes drilled and threaded for standard spur gear mounting, 3/16 x 3/8 bearing (#3977, same as axle bearing) in the spur to keep the gear spinning true, a rear axle spacer #7377, and the standard slipper spring and nut just to keep the stuff on there.

The slipper clutch was designed to help save on wear and damage of the drivetrain when accelerating and landing of jumps for modified motor racing. The silver can mabuchi 540 motors really don't make all that much torque or rpm compared to a modified motor, so I think the wear would be minimal, thats something you have to decide though.

First two pics are the drilled B4 hub with no slipper, second two pics are the old stealth slipper hub retrofitted on the b4 topshaft.

party_wagon

iTrader: (29)

First off, I would use the slipper. The mabubichis don't spool up very fast, but they do have a whole lot of torque when they are geared properly. With a good matched pack they will be just about as fast as a stocker on the track. Get the losi or associated, the car will be much much more durable, lighter, and it can run a much bigger variety of gears. The typical stock motor in a b4 is geared at around a 81t spur and a 23 t pinion gear. This leaves room to drasticly decrease the drive train from like a 8.5:1 ratio to like a 5:1 gear ratio which is more then capable of giving you the speed you need.
Losi has released a new buggy, the xxx-cr which is more durable and handles better than the bk2. However, now you may be able to find bk2s in good condition for around $100 used instead of a new $230 xxx-cr. The rc10 b4 is a great choice too.