YZ10 Works Projects

[stickboy007]

Yes, you are right about the rear tower on the '93 vs. WCS. Forgot about that. I think you're also right about the top deck pivoting on the center post. The double posts in the WCS wouldn't help too much, since they are in the same lengthwise position; however, the double posts in the '94 are offset along the length of the chassis. This results in a longer effective anchor and will reduce chassis flex accordingly. I'd expect you'd still run into a problem on hard landings, though. Even with double posts, you still adjust belt tension by flexing the chassis, so it stands to reason that the top deck can still slip on a hard landing. This is why I think the turnbuckle for belt tension adjustment serves a dual purpose.

Flustorm, you can get in touch with Chad at dyno-tech racing and he should be able to whip you up a new set of delrin arms if you need them. He has made them before for the Works YZ10 models. I have one of those sets installed on the '91 Works posted earlier in this thread.

[flustorm99]

So really flexing the chassis to tighten the belt, as was my issue too, means you really need to make sure the front two screws that attach the topdeck to the bulkhead hold as tightly as possible, with them being plastic its a tall order. So the larger the screw and thread the better holding power. Possibly a better way would to be to put a belt tensionor on the underside of the topdeck. I think mine must of had this in the past as i have two whole for where one was probably attached.

The arms are rather expensive from dyn tech arent they? Managed to grab a full set off a member here for half of what they were asking. Really want an original set if i can find some...i will keep looking..only ones i see tend to pop up attached to cars.

You do have some really nice cars there sticky, the black n white Senna paint job looks trick...i got a bit of painting to do but its far too cold here now...

[stickboy007]

Thanks. Glad you like them. Whenever I paint in the winter, the trick I use is to paint in the garage and place the body hear a small space heater. First use the space heater to warm up the lexan and help the paint stick without balling up. Then, immediately after applying each coat, place the body with the inside of the body facing the output of the space heater. It helps the paint dry faster and keeps it from cracking while drying. I've done several bodies that way and, in my view, I get better, more consistent results than waiting for air drying.

As for the top deck, a belt tensioner roller (like in the 870c) won't help if the top deck is still slipping. The loop that the front belt forms is kind of like a triangle rather than an ellipse, with the top-to-bottom spacing shrinking as you approach the center pulley. If the roller is fixed to the top deck, the top deck slipping will move the roller along the belt and change the tension. You could put the old fashioned spine into the bottom of the chassis and attach the roller there. That could work, but that's not Works fashion

Assuming the hole I drilled in the rear bulkhead cap doesn't blow up due to a hard landing pressing the tensioner turnbuckle back against the bulkhead cap really hard, I think this is the better way to go, since the turnbuckle allows finer tuning of the belt tension anyway.

As for the arms, you are right - the Dyno-Tech arms are rather pricey. If more people ordered them, I'm sure he could drop the price, but that's just how low volume orders go. Short of getting a 3d printer or finding spares, you could try using 870c rear arms, or 870c front arms with the outer hole for the wide conversion. You'd also need the 870c C-hubs, steering knuckles, and wheel hubs, but at the end the total width should be the same or pretty close. Those parts are generally easier to find, although I'm not entirely sure you'd really need to go that far. The Works arms are rather beefy and it looks like you'd have to hammer on them pretty hard to break them. Then again, you're running on a 1/8 scale track. I would say that if you're that worried about breaking the arms, then spend the extra money on a Dyno-Tech set. They are extremely strong and you won't have to pull your hair out scouring the web for them.

[flustorm99]

So with the belt tensioner...what if you set the topdeck to its innermost slackest position then tension it? So there would be no more losening or moving of the deck on landing? May work...

As for the arms i was looking at Masami's 89' setup and your right he basically pre-empted the wide front sus arms by using 870 rears and then made a custom rear set. So its funny you mentuon that as it was something i was about to try...but not being able to use the right c hubs would be a bummer...i do have the dyno tech arms but they are in my shelfer...maybe i should swap em with the drescher arms i have on my shelfer (i did have it like this but they arent pristine) so if i cant fond some new original ones i think i do as you say...i havent come close ti breaking them as i dont push the car too hard on the bigger jumps or the quads.. Its a 'just in case' scenario...i have about 8 pair of rear arms for the 93....a trade would be good too...

Anyway i just got a Bmax iii today so that will be the car i can go hard with...

[rccars4sal]

I got a bmax4 factory a while back. I really like where Yokomo has gone with their designs. Unfortunately,, everybodys going there, and so once again, its a cookie cutter playing field. Such is racing I guess.

[stickboy007]

Well, AE just released the B44.3, which is basically a Bmax-4 III with a top deck. The Lazer ZX-6 is much the same. The Losi 22-4 is just a beefier XX-4 (not necessarily a bad thing). I think the CAT and D413 are probably the largest departures as far as design goes, but ultimately they must all follow a similar trend to keep up with evolving track surface/designs - harder tracks with bigger jumps and higher traction. I saw a rumor somewhere that the next Worlds will be on concrete? I wouldn't be surprised...

Setting the top deck to the loosest position before tensioning the belt is possible, but that sets your baseline chassis flex toward one extreme. It might be simpler to have a top deck without slotted holes which has the right tension as-is, and then attach a roller if need be. It just so turns out that rccars4sal's 870c top decks manage to do this. I mounted one on the Works hybrid project (I really need to post some pictures of that...I'll do that soon) and it gets the job done.

As for the arms, yes, I got the idea from Masami's '89 car. Nice coincidence. I remember seeing the RCCA article for that on here somewhere.

[rccars4sal]

My design theory is that the top deck and chassis should be flat. If the chassis is a plate, with no kick up, then it should be in a relaxed state, and flat. Ive been using either no tensioner, or a pully tensioner on all my 870c builds. It depends more on the belt and production tolerances for the chassis weather or not it(870) needs a tensioner.

[flustorm99]

Yeah i have been watching some old ifmar races and some new ones, and really they may as well run on a different surface as the tracks seem like concrete anyway with only the jumps where u need the offroad setup for...personally i like the older tracks where you had all kinds of terrain thrown at you..more of a drivers track..so many things could go wrong which seems to be more challenging....in a way our 1/8 track is a bit like that here...not perfectly smooth with jumps here and there...there are smooth sections, bumpier sections, all kinds of different size and angled jumps...some are a bit over the top..but a good mix.

I just modified an old 91 rear shock tower and put a traxas rear wing stay and down force wing, partly to do away with the flimsey wire setup and mostly for this track..came up ok...i gota post alota stuff too but havent quite finished tweaking my old yokes yet...

Sorry if i am going off topic..back to your amazing builds

[hondaman]

My design theory is that the top deck and chassis should be flat. If the chassis is a plate, with no kick up, then it should be in a relaxed state, and flat. Ive been using either no tensioner, or a pully tensioner on all my 870c builds. It depends more on the belt and production tolerances for the chassis weather or not it(870) needs a tensioner.

I agree with you on this totally.. I think that using a belt pull tensioner is a better bet for consistent belt tension and a flat chassis at least for the 870C based platforms.. I would venture to think this would give more consistent suspension geometry and less belt slipping.. yea it adds a couple grams but that would be negligible.. I think this is a good topic for the 870C based cars to be used for runners.. stickboy007's works 93 is a great example that I am going to use for my "mule" project.. btw, I'm in the final stages of some 3rd printed parts for the 870C cars.. have a couple to do some test fitting on still and I'm looking at working out a modified bulkhead cap for mounting the turnbuckle.. I'm keeping an eye out on this 93 to see where it goes..

Shawn

[flustorm99]

True for 870...not so for works 91 onwards i dont think..otherwise why would they allow for you to tension via the top deck? It actually does flex the chassis and you cant get around that fact really...hence prolly not a good design...in saying that it only seems my 93 seems to go a little lose...the 91/92 seems fine but they all work on the same principle i think ie when u tension the top deck it will either push towards the front or rear bulkhead making the chassis flex somewhat...in reality the rear tension is sorted by the fact you can slode the bulkhead back and forth so we 'should' be only really talking about the front belt here...now making it possible to adjust the tension via mounting holes on the front bulkhead (like the rear) would make more sense and only have the top deck to stop too much flex in the chassis....unless i am off target here?

[hondaman]

What you say isn't too far off the mark in my book.. but after stickboy007's problem with the rear bulkhead I would think that an adjustable front would make the problem worse.. this would allow the front to be able to come out of adjustment on a hard landing as well.. maybe not back and forth but twist like it seems to be happening inthe rear.. My thinking by using a separate tensioner is to keep the front and rear bulkheads static and not use the chassis flex to adjust the tension.. I'm of the camp of KISS (keep it simple stupid... no I'm not calling anyone stupid) to keep things easy and rugged.. to me, the chassis should be static as it's own system and belt tension should be it'sown system.. using a tensioner is a simple way to keep the belt nice and adjusted and the suspension allowed to work on the static base of the chassis.. IMHO..

Shawn

[flustorm99]

Yeah i agree too..i think i mentioned doing that straight up? Really if the holes are drilled correctly with no slop there should no swivell either...only forwards n back....anyway i will see how my theory goes and report back..and probably do as u suggest...ha!

[stickboy007]

I should clarify/reiterate here that it was the top deck slipping against the rear four screws, and not the rear bulkhead slipping. The rear bulkhead sits just fine, because I can really tighten the mounting screws under the chassis. There is also the rubber gasket which helps to keep it from slipping. The aftermarket top deck is glossy/smooth, and the screw holes on the rear bulkhead cap that it mounts to appear to be partially stripped out. That means I can't tighten the two rear screws on the upper deck all the way down, and so the only thing really preventing the upper deck from slipping are the two smaller screws that go through the upper deck and into the motor mount. Short of getting a new rear bulkhead cap or maybe putting a rubber gasket between the upper deck and the rear mount screws (maybe that would work...not sure), the most pragmatic solution I can think of is to brace the upper deck at the rear with a turnbuckle. It is at least consistent with what was ultimately done on the '93 WCS and newer models, albeit perhaps for a different reason (finer tension adjustment).

My guess as to why chassis flex was invoked for tuning the belt tension is multi-fold. The flex approach was first introduced on the '91 Works, which came with 2mm pitch belts, which are more efficient than 3mm pitch belts. These are notoriously difficult to get just the right tension with and could be why, a few iterations later, the '93 WCS added the rear turnbuckle for finer adjustment (the WCS also had 2mm pitch belts, and was what Masami used to win the '93 Worlds). It ultimately comes down to what Masami was running, and I do not suspect that he would have wanted a roller adding both weight and drivetrain friction (remember, drivetrain efficiency was at a premium those days with 1700scrc packs) and would have instead chosen the lesser of two evils and opted for chassis flex. Sure, the added weight and friction would be minimal, but remember that Masami was the first of what I would call the hyper-tuners. He matched tire foams. He took the plastic casings off of his speed controls to save weight. A roller tensioner for him would be heresy as far as I can figure. The third option of only resorting to moving the bulkheads fore and aft, to avoid the need for a roller and avoid the need to induce chassis flex, ends up conflating belt tension with wheelbase and weight distribution. This ended up being kind of necessary for the rear bulkhead, since the rear belt is rather small and you cannot reasonably fit a roller in there, but there's really no need for it at the front, and at least the wheelbase part of it was compensated by the rear hub carrier being smaller than the fitting on the rear arms. That means you can move the rear bulkhead fore and aft and then get your wheelbase back by adding spacers around the rear hub carriers.

So...

If you wanted to be historically accurate, you would want to use the turnbuckle/chassis flex approach to adjusting belt tension, and there are good technical reasons to do so. This is the approach I am taking for this '93 Works runner. If you wanted to be more pragmatic for the club racer, then just throw a roller somewhere along the front belt, mounted to a fixed upper deck, and call it a day. I actually plan on doing that for the Works hybrid build

[rccars4sal]

I wonder how much extra drag a bearing supported roller would actually ad.

[stickboy007]

I'd expect the added drag and weight to be negligible at the club level, and especially with modern brushless motors that can power through just about anything. However, at the IFMAR level with old school DC motors, I would tend to think that drivers would squeeze as much weight and drag as they can away from the chassis, no matter how large or small of a difference it makes.