BloodClod's Schumacher Top Cat Project

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BloodClod
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BloodClod's Schumacher Top Cat Project

Post by BloodClod »

Hi guys, how's it going?

Been a while since I last posted a project but here's what has been keeping me entertained the last couple of weeks - the Schumacher re-release Top Cat!

I was very excited with this re-release at it seems such an interesting car with such a unique front end! Once it arrived I put it together and immediately hit the dirt with it. I had a blast but almost immediately wanted to see what I could do to improve it's performance and make this car my very own.

So here's my project Top Cat! :)

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Right off the bat I wanted to work on that front end. I know I wanted to retain those inboard shocks for sure but I wanted to improve their overall performance. Here's how that front end looks right now after weeks of testing and refinement.

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Another picture with a more close-up look. 3D printed top and bottom arms, upper arm pivot and also the cantilever.
Forgive the pink... it was what I had loaded in the 3D printer at that time. Since then I've printed new ones in black but have just been too lazy to swap them in. Besides, the pink has somewhat grown on me.

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I didn't like how the stock cantilever setup was not "connected" to the shock. The lower arm would push up on the cantilever on compression but it would drop on its own resulting in some strange handling (at least in my opinion) so the first thing I did was design a new cantilever to use a pushrod with rod-ends. I also wanted the pushrod to mount further out on the arm so I designed a new lower arm to go with it. It took a few iterations to get what I wanted in terms of performance and durability.

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With that sorted the suspension was working better but the front end had some crazy camber change as the suspension is compressed - largely due to the geometry of the front arms. I reckoned that a longer upper arm and a higher inner mounting point would go some ways in resolving this so I designed a new upper pivot and a new upper arm. Everything went great. An added bonus is that with the turnbuckle now I have easily adjustable camber on the car as well. The crashback still works and you can see I have added an additional rubber-band setup to give more tension to the crashback system so the front suspension can work better. With all this the camber change is reduced significantly and the front end works a lot better on the track.

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More pics and info to follow...

With these and some other mods I've done to the car it's really a lot more enjoyable to drive now on our demanding local dirt track.

Let me know what you think.

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Re: BloodClod's Schumacher Top Cat Project

Post by Dadio »

Top notch work as usual !
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Re: BloodClod's Schumacher Top Cat Project

Post by BloodClod »

Thanks Dadio. :)

I wanted to try to get the car closer to modern day specs so the wheelbase and width was something to tackle. I designed and printed 12mm hexes for the front and rear wheels. I found that a standard 5mm width hex worked just right with 4WD front wheels to get the proper offset. The rear was a tad wide so I printed the thinnest possible hexes that would work with the wheels. This brought the car specs much closer to modern day specs and allowed me to use the existing 12mm wheels and tires that I had.

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My cars get run under race conditions so they really undergo a decent stress test. After the initial few runs, it was obvious that the stock chassis, while strong, was not going to cut it as it was bent. I worked on a few different solutions and here's what has finally worked. A internal chassis-brace with ribs to beef up the car while allowing some lateral flex. It uses most of the holes in the existing chassis so it re-inforces the metal "tub" while not requiring any new holes to be drilled.

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As part of the chassis bracing, the rear part takes a lot of punishment so I integrated a rear turnbuckle brace as well that mounts to the shock tower. The car actually lands and runs a lot better with the chassis braced up as I think the suspension is allowed to do it's work.

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Here's a pic of the car with the chassis brace installed and all the electronics in. The battery is shifted to the mid-position as I find it offers a much better balance overall.

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Re: BloodClod's Schumacher Top Cat Project

Post by XLR8 »

Nice work on the internal chassis brace and that turnbuckle brace is a clever idea. Your car does not appear to have been abused, are you saying that your stock chassis bent under racing conditions?? Do you know if this was also a problem with the vintage Top Cat?
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Re: BloodClod's Schumacher Top Cat Project

Post by BloodClod »

The car gets run on a dirt track that is quite tough and rutted. The chassis bent simply tackling some of the jumps that in my opinion were not really that big. To be fair the tracks of old didn't feature any such jumps.

No idea if the vintage top cat was the same, but I don't see why it'd be any different. There just isn't a lot to brace against the chassis bending given modern tracks and power we run...

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Re: BloodClod's Schumacher Top Cat Project

Post by Asso_man! »

Really nice work. Will you make these parts available through Shapeways or the like?
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Re: BloodClod's Schumacher Top Cat Project

Post by BloodClod »

Thanks Asso_man, I've thought about putting up the parts I've designed on Shapeways but I'm wondering if there'll be issues with fit due to differences in printing tolerances. One possibility is to print the parts out myself to test but given where I live it would end up costing too much to do such testing. Maybe someone with experience might be able to advise.

Or if there are people interested in getting these parts through shapeways knowing this disclaimer I would be happy to make them available. :)

Image

The chassis brace has been perhaps the most important part I've installed so far to give me confidence to run this car harder. And I do enjoy how this car drives.

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Re: BloodClod's Schumacher Top Cat Project

Post by Retro rc »

Man that’s some nice work! I’d definitely be keen on a set of they went into production just finished my new built (re build) vintage top cat and have another to do that has a cougar front on at the moment, that would be good as a runner topcat
XLR8 wrote: Thu Feb 14, 2019 2:06 pm Nice work on the internal chassis brace and that turnbuckle brace is a clever idea. Your car does not appear to have been abused, are you saying that your stock chassis bent under racing conditions?? Do you know if this was also a problem with the vintage Top Cat?
Yep it was a problem right through the Ali pan series of buggies, especially as battery technology improved and tracks got more aggressive. The worst for me back in the day was the cougar 2 works chassis as it had some material removed at the rear of the chassis to increase suspension travel. I always had a spare chassis in my pit box just incase

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Re: BloodClod's Schumacher Top Cat Project

Post by DerbyDan »

This is definitely the best 'modified' re-re TopCat I've seen so far.... its amazing that this buggy has only been available to the public for about 3 months, but already cars like yours are 'sporting' such well resolved upgrades.

The chassis brace & inlay tray is especially neat. I must admit that in the past I've never had any issues with the TopCat/Cougar ali-pan chassis bending - even when running my re-built Cougar1 with modern electrics & on modern tracks (high grip + big jumps) - however, during my first meeting with my re-release TopCat - I hit a wayward car that had skipped over onto the main straight just as I was travelling flat out down it - the impact was (as you can imagine) pretty hefty...… but was still quite surprised to find that the chassis had indeed bent.... hearing other people's experiences of bending chassis on their re-release TopCats makes me wonder if the bead blasting process (to give the textured appearance) actually 'normalises' the surface - taking out the tension from the pressing & making them softer & more prone to bending?

I also like that you've addressed the camber change issue on the front suspension - due to the angle variation between the upper & lower arms, it causes the track width to increase as the suspension compresses - this I think is the single biggest flaw in the TopCat's front suspension design - everyone seems to be a bit obsessed with the ratio of the rocker movement - but I think this is less of an issue - more that you do need to re-think spring & damper rates.

I would be very interested if these parts were made available to the 'masses' - perhaps there are other 3D print suppliers (instead of Shapeways) that can offer a higher quality/stronger part??

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Re: BloodClod's Schumacher Top Cat Project

Post by Patrase »

Those parts look great. I have become a bit obsessed with my Topcat. I have modified rockers and the narrow track front end and it made a big difference. I would be keen if those part were made available. My next mods were going to be to fit spacers to make the front end geometry, in terms of the upper and lower arm relationship, a little better.

The chassis brace looks good - the track I run on has a few large jumps and I am sure your chassis brace would help.

In terms of 3D printing I had some stuff done locally that was much cheaper than Shapeways, haven’t yet tested the parts but they seem okay.

Would you make the files available or just sell via Shapeways?

If you are on Facebook join the Vintage Schumacher groups, would get a good gauge of interest in your parts

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Re: BloodClod's Schumacher Top Cat Project

Post by Kedal »

As other says, you make a really good job with your top cat! All is useful, well thinking and well done.

Love your lower front arms!!

As the tires mounted on it lets imagine, i suppose you drive it on dirt.
You don't have understeer problems? Seems you dont done any steering mod.
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Re: BloodClod's Schumacher Top Cat Project

Post by RCveteran »

Any ideas getting rid of the front crash back system all together? I recall it geing done back in day with a turnbuckle but with rere now maybe we can get a bit more creative. I need to stare at mine for a bit.

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Re: BloodClod's Schumacher Top Cat Project

Post by Chadz »

Love this! Excellent mods! What motor do you run?

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Re: BloodClod's Schumacher Top Cat Project

Post by MotoRapido »

Nice work on all the mods to the front suspension setup, you mention that you might be willing to share the files or put them up on Shapeways.
would you still consider doing that as i would certainly be interested in set, although possibly not in pink.
Busy resurrecting my Original Topcat from when they first came out, and its been sat in my Dads loft for about 25years.
tyres were shot and its needed a full strip down clean and rebuild.

will start my own thread once its up and running in standard form, but like the extra adjustment you setup could give.
does it also incorporate the narrower front track ?

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