Hopup vs Homebrew - a CC01 project thread

[Mad Ax 3040]

This is something I've been meaning to do for a long, long time, and now that the days are getting shorter, the weather is getting colder, I've got less spare time and absolutely no money, I figured it was just the right time to embark on an expensive, time-consuming outdoor project.

The premise is simple.  Take two of Tamiya's much-loved CC01 chassis, set them up in identical trim, then pit them against one another in a series of challenges.  Where possible, Hopup can only be improved by fitting commercially-available hopups, and Homebrew can only be improved with home-made modifications.  Beyond that, no holds are barred!

To set a level playing field, both chassis have been built with full bearings, shimmed rear axles and GPM steering kits.  Homebrew actually has steering arm turnbuckles, but that's just because they were already attached to the GPM steering kit when I took it out of my parts box and doesn't represent any cheating on Homebrew's behalf.  Hopup is identical apart from the turnbuckes.

Both rigs run the same steel pinion, Alturn AAS-750MG high-torque servo and Hobbywin Quickrun 1080 crawler speedo.  Homebrew runs an ORX receiver off my trusty Spektrum DX3C transmitter and Hopup uses a 6ch Turnigy stick combo (primarily because that's the only spare radio I have).

Homebrew is the white rig on the left, Hopup is the grey one on the right.

[Mad Ax 3040]

Stage 1: Tyres

The eagle-eyed among you will notice that Homebrew is wearing cut staggers.  This was a popular mod to the Tamiya BFG tyre way back in the day when there were no other tyre choices available.  Opening out the tyre buy cutting off every other tread gave better traction on a lot of surfaces.  These tyres are actually from back in the day, too.  They were on my first ever trail rig, a Baja F150 converted for trail duties.

So the initial test is to see whether the cut staggers really are better than the stock tyres.  With limited time but unexpected good weather, I set off today to the a little local area with two good slopes.

 

[Mad Ax 3040]

It's a little valley that might once have been a stream (no water has flowed down it in the 5 years I've been walking there).  The sides are steep and there's some tree roots for good measure.

I actually took some videos of the attempts but sadly they didn't focus properly.  We'll call this a practice round.  Maybe I'll edit them and stick them up later anyway...

I set off with Hopup first, with the stock BFG tyres, and did the slow descent.  It performed well, losing traction half-way down but maintaining enough control to reach the bottom.  Somewhat surprisingly, it handled the climb back up again with too much bother as well.  I had expected it to get stuck at the bottom.

With the gauntlet thrown down, Homebrew had a lot to live up to.  Again, it handled the descent well and did the return climb with no issues.  After a couple of back-to-back runs I decided Homebrew had a little extra control, but both rigs were able to get up the slope without much bother.  Pretty awesome attempt for stock CC01s, I thought.

I then tried the slippery slope opposite.  Smoother, with no roots or dips, but a slimy surface that offered very little traction.  Hopup went first and, predictably, got stuck.  And then got unstuck.  It wouldn't climb the 'proper' way, with the wheels turning slowly, but given full power it slid and squirmed and bounced and eventually found some traction on a bit of moss.  Technically that would be a fail because my self-imposed limits didn't allow me to go on the moss.  But it made a climb that I honestly didn't think it would make.

Again, Homebrew had something to prove.  Were the cut staggers going to get me up where the stock tyres had failed?

Answer: no.  I was surprised to find that Homebrew got stuck fairly early on and just wouldn't climb.  In fact, after a few attempts, I had to get Hopup back over to work out how I'd done it the first time.  Sure enough, both rigs would climb where there was moss on the back but neither could handle the slippery mud.  Homebrew's hacked staggers made more of a mark on the surface but couldn't bite in deep enough to climb properly.

If I had to choose which was the best tyre, then Homebrew seemed to go better where I was trying to maintain traction and keep over-rotation to a minimum, but Hopup was smoother when I gave it full beans and got up on brute force and raw power and maximum slippage.  Ultimately, neither tyre was really up to the job.

I think I expected a bit more of the cut staggers, but I think this shows how far tyre technology has come along.

Now, technically, Hopup should have had a second chance here to take the lead using a Tamiya hopup tyre, but unfortunately I forgot to bring them.  Given that the test is so far inconclusive, I intend to take a long lunchbreak on Friday so I can make the 20 min journey to a better crawling spot for some real tyre tests.

See you next episode!

[Badcrumble 1931]

A great read! Thank you for taking the time and effort to document your adventures.

[Mad Ax 3040]

No problem @Badcrumble.  My original plan for this was to video the whole thing, including me talking about the project and doing the mods, and make it part of a new youtube channel.  But having had a practice-run at recording some stuff the other week, I figured I'd need to spend a lot of money on lights and clip-on mic, my point-and-shoot camera couldn't auto-focus on the detail stuff, and I was going to be left with two hours of footage that would take me a week of evenings that I don't have to edit down into a 25-min episode.  Plus all the graphic design, music and animation that I'd have to do to polish it all off nicely.

Anyway, I didn't really have the time to sit on this any longer because I'm lending Homebrew to a friend for a local crawler event in under a fortnight and I want to cut the brick first.  That means I have to get all the stock-chassis tests done first.

I'll take the tripod with me next time and try to get some static photos done if the video isn't going to work well.  This felt like a bit of a lame start, which is a shame as the weather and conditions were absolutely perfect.

Hopefully I'll be able to do Stage 1a: More Tyres on Friday

[speedy_w_beans 3922]

This is interesting; I'll be following to see what else you compare.

[87lc2 772]

Great idea, thanks for posting.  Your spot looks very similar to the trails around my house.  That slippery looking hill is definitely a tricky one, will need a soft compound to get up that using crawler speed.  There are many hills like that on our trails and I upgraded tires on a few trucks specifically to climb hills like that.  In 1.9 size I'd highly recommend the new RC4WD Goodyear Duratrac tires (3.85 diameter).  I run them on my M1025 Hummer and they are absolutely amazing.  Stock Tamiya tires are just too hard for slopes like that, but still good to hear they made it up with some wheelspeed.  

Looking forward to more of this comparison, great idea.

[Mad Ax 3040]

Thanks for the tyre advice @87lc2.  I have two sets of Kong tyres left over from other projects - they're not brilliant but they're matching and they're mine, and as I'm now on a really tight budget they will have to manage as the control tyre.  Maybe if I get a cash windfall and I'm really struggling for traction I'll buy two sets of better tyres next year.

On Friday I'll hopefully be doing a back-to-back with the BFGs, the Kongs, and a set of Hi-Lift tyres that I have spare, provided the weather holds and time works out.  It will be interesting to see if there's any appreciable difference.  Also yesterday I placed an order for the next two rounds of hop-ups, so I'll have a few more updates to do yet.

[Juls1 1236]

Having been through most of this myself but undocumented, the one single thing that makes more difference than anything else is ultra soft sticky tires with super heavy steel and alloy rims. I’ve made plenty of axials and vaterras look stupid basically because my tire/wheel combo was better. That being said a decent wheel/tire combo will set you back the best part of $100usd or quite a bit more. There is very few if any shortcuts here. Decently soft tires will be so soft you have to sit the car on a stand when it’s not in use to avoid causing severe flat spots in the rubber and foam. The tire should look like it needs air when in use.

Secondly setting up the suspension so it can obtain max flex under its own weight, this can include adding weight to the chassis. Also grinding out everything that’s limiting travel up front. Especially if your running the cc01 alloy dampers as they have more travel than the stock cva’s. 

And finally, my first cc01, like many of you was the old Paj, the hardbody one. 

When I built my 3rd cc01 I opted for the newer paj shell which is polycarbonate. It was then I realised that the heavy pvc body was strangling the chassis’s capability’s because there is far too much weight up high in the car making it very unstable in almost every scenario, at least compared to running the poly shell anyway! (Of course the pvc shell is probably more realistically weighted but when it comes to who made it to the top does realistic come into it??)

These things are the most important for cc01, that’s assuming you’ve sorted the steering (yeah racing kit probably the best imo) and the rear linkage. Obviously locked both diffs. 

Now if you start cutting up the whole front of the car (which I assume you’ll do with the home brew cc01) there might be some gains to be found there. 

I’m glad you’ve decided to use a control tire. Those old cut up tires are cool but I think there would be quite a few scenarios when you’ve just put less rubber on the ground which equals less grip.

[87lc2 772]

Exactly what Juls said, tires/wheels are everything with the underdog Tamiyas in the crawling world.  My Hummer with RC4WDs stickiest compound tires & aluminum beadlocks with wheel weights will keep up with my fathers TRX4 Defender, its almost unbelievable to watch the little TA01 go.  Of course I have a custom chassis, locked axles, etc, but still at an extreme disadvantage with the independent suspension setup vs solid axles with portals.

I think its great your'e trying what you have on hand, will be keeping a close eye on this thread.  I've never really had a reason to get a CC01, but this is making me really want one, they look pretty cool.  Too bad they're a lot more expensive than they were a few months ago...

[Mad Ax 3040]

7 hours ago, 87lc2 said:

Exactly what Juls said, tires/wheels are everything with the underdog Tamiyas in the crawling world.  My Hummer with RC4WDs stickiest compound tires & aluminum beadlocks with wheel weights will keep up with my fathers TRX4 Defender, its almost unbelievable to watch the little TA01 go.  Of course I have a custom chassis, locked axles, etc, but still at an extreme disadvantage with the independent suspension setup vs solid axles with portals.

That's interesting.  The old TA hybrid chassis are surprisingly capable.  A year ago I went to a local crawler meet, complete with gates and everything, with my SCX10 on big Class 2 tyres.  I brought a mate with me and the only running scaler I had besides the SCX was a Hummer on a stick chassis.  I bought it on a Facebook trade and consigned it to the projects box to look at later.  Took me a few minutes to slap in a speedo, servo, 55T motor and a set of Kong tyres onto the stock rims (in fact the very same Kong tyres that I'll be using on Homebrew as the control tyre) and we went out and hit the gated trail.  I was amazed that it managed to do as well as it did.  It's going to be a very capable little trail rig when I finally get around to finishing it properly.

[Mad Ax 3040]

So, it's a week late, but here's the nest installment of Hopup vs Homebrew!

Stage 1a: More Tyres

Stage 1 was a rather impromptu last-minute the-sun-is-shining-and-I-have-fifty-minutes affair.  That fifty minutes included packing up the cars, reassembling the camera, finding some batteries, driving to and from the venue and towing a trolley loaded with all the stuff to the test site.  Amongst all that I forgot to take the control tyres, as well as the Rock Cruiser M/Ts that were going to act as the hopup tyre to test against the cut BFGs.

A week later the weather forecast was looking good, so I started work an hour early to get a good 2 hour lunchbreak in the sunshine.  Of course this is a British autumn, so by lunchtime the sunshine was gone and the ground was sodden from from a torrential hailstorm.  But never mind - the hail was gone, the clouds were clearing, and I'm not made of salt, so I figured it was worth a trip to the country to test some rigs.

The challenge area this time is a good 20 minute drive from home, actually longer on a Friday lunchtime it seems, thanks to heavy traffic and people driving very slowly.  But a 30 minute drive each way (to do a handful of miles) still equates to 60 minutes on the trails, and that's not a bad way to spend lunchtime.  The hailstorm meant the location wasn't overrun my mountain bikers either.

The site is a little patch of woodland called Coulston Hollow, on the very northern edge of a large artillery firing range and tank testing ground in Wiltshire.  As such it's pretty quiet (provided they aren't shelling) some of the mountain bike tracks are perfect for trailing.  A lack of rocks means it's not that good for proper rock crawling, but for a CC01 trail test, it's perfect.

 

[Mad Ax 3040]

[Mad Ax 3040]

The rigs themselves were in the same condition as last time: mostly clean, a bit of mud on the tyres, stock chassis (apart from bearings, GPM steering kit and shimmed rear axles) and matching electronics.  Hopup was wearing stock BFGs, Homebrew the cut staggers from last time.

 

The first test was to hit a few of the obstacles pictured above with the stock BFGs.  Once again, the CC01 surprised my with its ability to tackle every obstacle thrown at it.  Sure, my SCX10 would have done the same with less fuss, but there wasn't much the CC01 wouldn't climb without a run-up.  I had to find some tougher climbs to really test the tyres.  Eventually they met their match with a long, steep, muddy slope with a big tree root at the top.

Homebrew went out after, to see if the cut staggers offer much improvement over stock.  As with the last test, the difference marginal.  They worked best over the rotten logs pictured above, where the treads acted like claws and dig into the wood.  Nothing is really going to help on leaves, and on mud there just isn't enough weight in a CC01 to push the BFGs down into it.

Next I fitted the Tamiya Rock Cruiser M/Ts to Hopup and a set of Boom Racing KRTs to Homebrew.

 

The Rock Cruisers are quite old - they came on the Land Cruiser 40 chassis that I got used a year ago and forms the basis of the Homebrew build, so it's perhaps not as fair a test as I'd like it to be...  As the tyre diameter is bigger, I had to lift the body by one pinhole.  This episode isn't about body mods, so I didn't want to do anything irreversible.  Besides, being a lexan body, it really doesn't make much difference to the CoG to bring the body up a bit.

The KRTs are mounted on some odd beadlocks that only seem to fit the KRT tyres but which seem to deform them in an unusual way.  These tyres aren't quite as tall as the Rock Cruisers (the difference is marginal) but I still needed one extra hole on the body posts.

I may buy a new set of pre-mounted KRT wheels and tyres later, if I can get a good deal on them.

So - badly mounted and dried out, how did they perform?

Well - not bad at all.  The Tamiya tyres worked really well everywhere I threw them.  The added ground clearance kept the brick off the dirt and the tyres had plenty of bite over the rotten logs.  They were pretty good on leaves and dirt too.  I got most of the way to the top of the steep muddy slope before the root stopped my progress.  They also worked well when attacking obstacles in a scale fashion - gently on the throttle, with minimal slippage - rather than using speed and wheelspin, like with the BFGs.

But the KRTs, despite being a slightly smaller diameter, were better.  For a budget tyre (pre-mounted they're less than £10 a pair, if you shop around) and fitting neatly into Tamiya arches with only one extra pin on the posts, they're very good.  Sure, a proper soft tyre from RC4WD on some heavy alloy wheels is going to beat them, but these aren't to be sniffed at if you're on a tight budget.

In most places the difference wasn't huge - they climbed the logs, the handled the rooted mounds, the went around the mountain bike track.  The final test was the steep slope, and they got up that with no bother.  I thought the root at the top would stop them, and sure enough, they couldn't climb right over it, but they helped me to find a way around the root that none of the other tyres could get over.  At last - a clear victory!  The KRTs succeeded where all other tyres had failed.

 

So - that's this episode done.

Next time - skid plates!  Another big CC01 weak spot - the front brick - gets two very different treatments in an attempt to keep it off the ground.  Catch it here on Tamiyaclub soon!

[87lc2 772]

Interested to see what you do with the front 'brick' to gain some clearance.  I'll definitely have to get a CC01 soon.

[Mad Ax 3040]

WOW - such a long time since I updated this thread!  To think, when I started this project, I was determined to do at least one update every month.  Of course the world was very different back then, but I can't blame #becausepandemic for this one - nor can I blame my own innate laziness.  Well, not entirely.  The problem was that I had ordered a Junfac front skid plate for Hopup and had already gone ahead and made the Homebrew skid plate while I waited for delivery.  And then delivery was delayed.  For over a year.

I chased the missing article a few times but I should have given up and ordered elsewhere a lot sooner, in order to keep this series on track.

Homebrew actually got loaned out at a big local quarry meet as far back as early winter 2018, and it did surprisingly well on a course designed for bigger and higher-spec machinery.  I say "surprisingly well", I mean it got hammered seriously hard and driven at the scenery as fast as it could in order to smash through the obstacles.  As it was a quarry and the scenery in question mostly consisted of jagged rocks, the skid plate got a proper bashing and more than proved its worth.  Did the CC01 keep up with an SCX10 on sticky Class 2 tyres?  No, not at all.  It got around the track, mostly by being pushed, pulled, kicked or even carried over the tougher stuff.  Much as I love the versatility of the CC01, a "no hand of God" rule cannot apply to a truck like this with so few mods.

Anyway, I digress.  I previously documented the skid plate build as a showroom entry but here it is again using the words of today (and not the words of 2 years ago when I built the thing) linked from tcphotos as this is how I prefer to do things.

I started by hacking at the CC01 chassis to give a nicer angle of attack, removing pretty much everything that isn't essential.  I've done a similar job before and I left a bit more meat on the front of the chassis (there is a single central screw hole ahead of the bottom arm mounting plate that I used to fix the bottom of the skid plate), but this time around I wanted a shallower angle of attack so I cut that entire area away.

To secure the top part of the skid plate, I made this bracket from 10mm delrin plate.  It screws into the top of the chassis.  IIRC I had to drill the holes for this as there are no standard holes here.

[Mad Ax 3040]

Next I turned my attention to the bottom arm mounting bracket.  This is an unusual part on the CC01 since it comprises the mounting point for the bottom arms, as well as a skid plate for the front diff housing and a cover for the steering cranks.  Because I was planning to mount my skid plate on top of the leading edge of this bracket, I was going to end up with even less clearance at the lowest part of the standard CC01.  Not ideal.

Here's the standard bracket:

Using a Dremel with a sanding drum, I took off the ribs to add a bit more clearance (which I would later take up with my own skin plate)

This is the area I needed to close up with my skid plate

[Mad Ax 3040]

Contrast the front end of Hopup:

Next, I set about cutting a skid plate from 2mm alu sheet.

While bashing it into shape, I tried to countersink the mounting holes.  It didn't work too well and later on I would revise this section.

Smashing the whole thing into shape took a bit of work but ultimately the result was tidy.

[Mad Ax 3040]

I had to file some meat out of the top mount to clear the arches

Countersunk screws didn't sit as neatly as I wanted.  I would later file these down but I was never pleased with the result.

fin.

[Mad Ax 3040]

So - as I mentioned a few posts ago, this rig did get some use at a local event, but didn't get a chance to compete against Hopup because the aftermarket skid plate never arrived.  It was only recently that I got to take the two trucks out together.  Even then I had a few false starts - Homebrew had become unbound in the months that have passed and I didn't have a bind plug; my camera battery was flat; I didn't get good side-by-side pics of the skid plates; the terrain was too dusty for either rig to do much beyond skid and bounce.  Homebrew disappointed me by getting its new sump plate caught up on stuff - I wanted to show that a few hours cutting, drilling and bashing would give a significantly better result than a £15 part from China, but in the end it was inconclusive.  Homebrew has a better angle of attack ahead of the wheels, but has a lower ground clearance between them.

Clearly, things needed to be done.

[Mad Ax 3040]

Here's the problem area.  Despite my vicious Dremel attack on the stock sump, my mod was still taking up space under the truck, and the countersunk screws were catching on anything and everything.

This is how much meat I originally took off the bottom bracket.

An here's how much I took out this weekend, with a Dremel sanding drum.  Actually, to Dremel sanding drums, both of which explosively delaminated, giving me a graze on the forehead in the process.  WEAR EYE PROTECTION.

[Mad Ax 3040]

I had to trim a bit off the bottom of the skid plate and reprofile it a little, but it now sits much neater against the bottom of the chassis.  Dome-head screws are a nicer solution.  Potentially I could use countersunk screws if I had a countersink drill that would work on alu.

Further pics and a comparison report to follow once I've had time to finish the latest updates to Hopup and get out on the trails again.

[ChrisRx718 2516]

Nice!

None of my CC01s are capable, not even remotely. They're scale toys for running around the garden, I think you would have to do too much to a standard CC01 to make it half-capable!

Loving your work. I could taste the Dremel-on-Tamiya plastic shavings when reading your experiences. We've all been there. I have a scratch on my 'good' pair of glasses from an exploding cutting disc, too, so they definitely don't count as eye protection! 

[Mad Ax 3040]

The next step in my Hopup-vs-Homebrew challenge is to 4-link the rear suspension on both rigs.  I am kind of getting a little ahead of myself here because I haven't tested my latest changes to the skid plate, but I should also add that due to restrictions in free time and waiting for ideas to come, I'd already started on the 4-link setup before I made the latest mods to the skid plate.  So the next run will have Homebrew with an updated skid plate and custom 4-link and Hopup with a Junfac 4-link.

So, how do we 4-link a CC01?  There are a few ways, but first thing you always need is links.  You also need a way of attaching said links to the axle, which is fairly easy, but unless we're planning on extending the wheelbase and/or totally changing the rear end, it's the shock mount that's the problem.

Here's a standard setup:

The standard CC01 axle has nice mounting points moulded in for the links, but it has no eyelets for the shocks.  I know this makes a nice clean axle, but still seems like an oversight to me, especially as the shock mounts on the back of the plastic links are ugly as sin.  I don't know if this is based off any 1:1 assembly but to me it just looks wrong.

First thing I did is stripped off the rear axle.  Fortunately the CC01 has plenty of mounting points on the chassis for adding links.  I want to keep the stock wheelbase, so I'll be using the stock mounting points.  For now.

Here's the underside of the axle.  Lighting isn't very good but you can see a lil recess where the stock links go.  Actually they don't touch in the stock setup, I guess the recesses are for clearance.

Now, we could mimic the stock setup by making a long link that protrudes past the end of the axle, which the shock could bolt up to - but that would affect the right height unless we extend the shock, and it wouldn't look right.  Also I'm not sure how I'd attach the link to the axle.  Another way is to buy an axle mount from ebay, which isn't in the spirit of the Homebrew setup, or 3D print something, but my resin printer makes brittle objects that wouldn't stand up to abuse.  So the next option is to make something.

I have to confess I deliberated over this for over a week, and started 2 different designs before I made something I was happy with.

[Mad Ax 3040]

This isn't the first time I've been here.  I made these link mounts for my F150 scaler:

They were made from 2mm alu and seem to work well.  They are contoured to fit perfectly in the axle recess to they don't move around and work the link screws loose.  However they were quite a pain to make, and I always worried the leverage on the back of the mount would bend it.

This time around, I considered making something that would loop over the top of the axle, so I started with this cardboard template:

Before realising I couldn't find my 2mm alu sheet.  3mm would be stronger but harder to work with, less likely to take a 90 degree bend, and would cost me an extra 1mm of clearance under the axle.