Dan's ProCat runner/racer project

[DerbyDan]

When I first started racing, 4wd in my eyes were the ultimate class, so the cars that I most desired (but could never afford to buy or run) were CATS, Optimas & Yokomos, during that first year or so racing at my local club, the venerable CAT XLS was replaced in the Schumacher line-up by the ProCat, being so young & enthusiastic I read up on everything about it & eagerly entered the competition in RRC magazine to win one. Alas I didn't win the competition & have never raced a 4wd buggy either back then or now. That last fact I hope will change very soon!

So, I saw this nice 'low run time' ProCat on ebay which didn't sell for its BIN price to I contacted the seller after the auction had finished & secured the car for a reasonable price... it was soon afterwards that I realised that the seller was in fact fellow RC10Talk.com member Moozo

The strip down began almost immediately after I recieved the car... unfortunately in the excitement I forgot to take some 'before' pictures but I managed to do a search through this section on the forum & found one of Moozo's threads with a photo of the car in question, this is basically as the car came to me except with 'natural' Trinity wheels rather the pink Yokomo wheels in the photo;



Most of the car is still in the dismantled state as a box of bits



I suppose I should explain my purpose for this build... I made my return to racing off-road buggies after building up the RC10 Worlds Car that is in my avatar pic... after enjoying the attention & challenge of running an older car against modern buggies I have been hooked in having a different vintage buggy available to race for each season. So in 2012 I had the Losi XX & last year I had the JRX2... this year I hope to have this ProCat as my 4th vintage buggy.... & my first ever 4wd racer!!!!

Onto the re-build, so far i've concentrated on collecting a few essential parts that I think will help keep it reliable & to be able to handle the power of the 8.5 Orion brushless motor I ran last year in the JRX. I want to make sure it runs reliably but I don't want any mods to detract too much from the vintage 'feel' of the car as I want the driving experience to be as close as possible to how it would have been 25ish years ago.

Here's a list of 'other' parts that i've collected;

2.2" Aerodish (BossCat) wheels - I had fronts but got some rears from Moozo
BossCat rear arms/hubs & mounting brackets (also from Mick)
1 Pair Hex diff outdrives + washers - i'll use these in the rear diff (again from Mick/Moozo)
Complete Bosscat slipper assembly inc' layshaft & pulleys (from Cat3K, Paul)
New belt cover from TBG
&... new shell/wing & undertray from Penguin (as far as i'm aware the only re-producer doing the original Schumacher shell - not the Racecraft version )

...I even brought a complete Kyosho Lazer ZX from which i'll borrow its gold Option House shocks, which were a common upgrade for the standard Schumacher items

Option House Golds;



BossCat slipper; looking at the BossCat instruction manual, I seem to be missing a shim that goes between the layshaft pulley (closest to the spur end) & the bearing - I wonder how essential that is?



Different diff outdrives; The car came with MMS diff pulleys both front & rear but only the rear had the matching MMS outdrives (far right in photo), I don't really like the method of glueing the diff rings to the outdrive so have 'plumbed' for the Hex Diff parts for the rear (where more loads are likely) & the original (black) outdrives on the front but using the kit method of gripping the ring to the outdrive using cut discs of 240grit wet & dry paper.



I noticed that the O/E diff outdrives have a recess to accept the corresponding 'peg' in the pulley - the MMS diff doesn't have this & I was worried about the bearing in the middle of the pulley being allowed to slide out - so I shaved down some old shock pistons & glued them into the recess in the outdrives, you should be able to see them in the photo above? I've since realised that these need to be thinned down a little as they were binding with the bearing when I tightened them up

Diff & driveshaft parts ready for assembly; I incorrectly thought that the new thrust-race shown would work since I found a similar thrust race in my parts box that fitted the TopCat that I've recently built. I didn't realise that the ProCat diff screws are actually 1/8" dia - not 3mm - the U3704 thrust races are obviously for an M3 screw & the centre hole is too small in all three parts - one of the thrust washers is also a larger dia (I can remember this from the Fireblade/Axis-SST days) & won't seat into the diff outdrive

[Incredible_Serious]

Are you sure these are Schumacher parts? They look suspiciously clean....

Loving the build so far.....

Alex

[DennisM]

Yeah, there´s something fishy going on here - someone´s even forgotten to hack saw the bumper.

[Peakey]

Looks good so far I will be keeping an eye out for any bits you have left over pal for my rebuild project I've got one cat in bits in the shed and one in the post from Australia

[CAT3K]

I pulled the layshaft out of my works, and mine does not have the shim either Dan. I suppose there is a slight amount of float, but nothing major from my point of view. If anything the running belts should keep the pulley central or you could fit a 1mm M4 washer (I think the layshaft is M4?) to shim it out slightly.

Paul.

[DerbyDan]

I pulled the layshaft out of my works, and mine does not have the shim either Dan. I suppose there is a slight amount of float, but nothing major from my point of view. If anything the running belts should keep the pulley central or you could fit a 1mm M4 washer (I think the layshaft is M4?) to shim it out slightly.

Paul.

Hi Paul, I can see why the shim would not be necessary, I think (judging by the BossCat manual) that the shim fits over the shoulder on the slipper end of the pulley mouldings, but it would have to be super-thin.. I think a small amount of end float is not a bad thing

Progress - Diffs/layshaft & shocks all built up;

[stulec52]

Looking good already Dan
My problem lately with trying to run anything old school is the fact that I only have lipos now.
I'll be interested to see how you deal with that

[DerbyDan]

Looking good already Dan
My problem lately with trying to run anything old school is the fact that I only have lipos now.
I'll be interested to see how you deal with that

There are plans a-foot - I want to use the shorty Lipo batteries that I use in my modern racer - I'm even contemplating running it as a mid-motor 2wd, so there is provision to move the battery forward to play around with balance.... watch this space!

[Peakey]

Is that a mms front diff aswel? And how did you get them so clean

[DerbyDan]

Good old washing up liquid & a toothbrush! - Maybe a little blast with some TF-90 just to get the last bits of old grease from inside the holes, to be fair though I don't think this car has a great amount of run time - maybe a dozen race meetings or so... so there is little in-grained dirt!

[Peakey]

Did you replace the bearings in the diff or did you reuse the originals? I was thinking of replacing mine with some ceramic ones. I have seen a kit that I think will fit and it comes with a thrust race the correct size

[DerbyDan]

I assume you mean the diff balls Peakey? I've kept the std steel balls as they looked fine - I must admit that i've never really believed in the hype surrounding the more exotic ball types (ceramic & carbide) - whats more important is keeping the diff well maintained - not to let it slip too much & regularly re-honing the diff washers to remove the pitted groove that gets worn by the balls - strangely using a course paper (I use 240 grit) helps for a smoother diff action since the rougher surface helps the balls to grip the discs without needing to tighten it up so much

PS; Making sure the thrust race is in tip-top condition is also important as any grit/dirt/pitting will amplify itself through the diff action.

[Peakey]

Thanks dan I was on about the diff balls I will strip then and have a look and see what they are like. Thanks for the tip on the sand paper I will have to try that. I have managed to get a nip thrust race and the reason I was considering changeling the diff ball was it comes with a thrust race the same as u730d

[DerbyDan]

Nice to have the new thrust race - is it the type with the little plastic cage? I left this part out of the thrust race assembly in my diffs, they just break up.... I added a couple of extra thrust balls in its place.

Regarding the honing of the diff washers - use wet & dry paper & make sure you place it on a nice flat surface before the honing process - I tape my paper down onto a peice of glass. Using your middle & index finger rub the washer onto the paper in a circular motion (occationally rotating the washer under the grip of your fingers) until the running line of the diff balls has dissapeared.

[Peakey]

That's the one I never thought of that I'll see if what the old balls are like to add them instead another very helpful tip thanks dan. I may have a spare set of mms diffs soon if you may be interested but I am waiting for something to turn up in the post before I can let the one I have go.