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Juggular

How does the suspension move like this?

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Seriously, are they using something I don't know? 

It's like the chassis is floating on clouds. 

 

 

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9 minutes ago, Juggular said:

Seriously, are they using something I don't know? 

It's like the chassis is floating on clouds. 

 

 

You mean your cars don't move like that? I just build to kit specs and mine float on clouds too, honest

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LOL...Oh, that was the funniest thing (to an old Tamiya fan like me).  

I love Tamiya, but Tamiya's idea of suspension is medium-hard rubber tires bouncing, (while springs stay frozen).  They are not shock-absorbers, they are shock-repellers.  They beat back the shocks! 

Jokes aside, I would love to see some of that floating action in Tamiya.  Or... is there a way to make it so?

Anybody made a really floaty suspension on a Tamiya?  I would love to know that it can be done?

 

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On a full size like that? The broad answer, in comparison to a street-driven vehicle, is soft with a ton of travel. That doesn't necessarily translate 100% to RC though. The TXT-1 has the weight to keep it planted (and respond more like a full-size vehicle), relatively soft suspension and a ton of travel. It generally floats over terrain like that but that doesn't make it a good track vehicle (despite being awesome anyway).

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The problem is that with RCs we have a warped perception of speed. It is easy to make a 1:10 RC drive like that truck by putting super soft springs in it and driving at 10-15kmh (100-150kmh scale speed) but most would be unimpressed with their RC not being able to do over 15-20kmh without bottoming the suspension. When you put hard springs/shocks in it so it doesn't bottom out at 50kmh+, it stops looking 'scale' from any vantage point as everything is happening lightning fast. If you drive it at 50km/h with hard springs and take a slow motion video, it does however look more realistic.

The Traxxas UDR is probably the best compromise I've seen. It's reasonably big and has soft and massive suspension travel, so it can go quite fast while still looking reasonably scale. In slow motion it looks 100% scale.

 

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Those professional racing vehicles (trucks, rally cars, etc) have about $50,000 USD in their suspensions alone.  I'm sure it's possible to develop a scale versions of a similar setup, but cost-wise wouldn't make it feasible.

 

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When I switched from my ECX Torment short course truck to a Losi XXX-SCT the difference was night and day. I gunned it across a rutted bumpy field straight toward me and watched the body stay stable while the suspension arms moved with ground similar to that vid. It shocked me so much I did it 3-4 more times just to watch it work. That's when I decided I needed some cars that performed well. I imagine the TRF cars perform similar, but I've never driven one so that is just a guess.

I still want that 1:1 truck though :)

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The other bit that makes it look like that is the weight of the body over the suspension.

There was a bloke on youtube who makes rc bodies out of wood to give them a lot of extra weight on the suspension. When you see them on video they look very very realistic. There was one of a mk2 escort rally car he made. Will try and find a link to the video

 

This one - how epic is that!!!

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6 hours ago, nbTMM said:


The Traxxas UDR is probably the best compromise I've seen. It's reasonably big and has soft and massive suspension travel, so it can go quite fast while still looking reasonably scale. In slow motion it looks 100% scale.

I was just going to say that too - I saw that Traxxas promo video recently and it is very realistic... but like you say, due to the scale vs our perception, you need to slow the video down a bit for it to look genuinely real.

Jx

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Basically because it's soft. The problem is that Tamiya stuff is 1/10 scale but gets used in a 1:1 sized world. 

Real life cars have it very easy compared to RC ones when it comes to terrain and how high they are asked to jump etc. Even racing trucks like this. 

If you put suspension like that on an RC it will bottom out easily even on relatively smooth terrain.

The best thing you can do is aim for a compromise.

You can get a pretty good approximation. The aforementioned Traxxas UDR and the new Kyosho Oulaw are good examples I've seen recently but I dont think you'll ever pull off that gliding effect without making big compromises elsewhere. I guess if you only drove on scale terrain at scale speeds you could do it but in reality, even a modest Tamiya tends to have much higher than scale speed and will be driven on out of scale terrain.

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I forgot about the scale effect!  (This is why one head is always less smart than many)  That wooden 1/5th car is awesome.  I'm amazed that Traxxas UDR can do it without adding a lot of weight. But I cannot afford that.  Also, I want my existing Tamiyas to perform well.  I don't own any Short Course Truck.  But if Losi can do it for $300, I'm sure there is a way to improve Tamiyas without spending $80 on big bore shocks.  

For the time being, as you guys have suggested, I'll aim for a compromise.  Matteo said he used 4-hole pistons instead of 2-hole pistons the instruction tells us to use.  His compromise gives me hope.  (I might experiment with the lightest oil or even no-oil options --- I only tried no oil on the front of M06 with good results)  

Does anybody know what is the lightest oil I can buy?  

 

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5 hours ago, Biz73 said:

I imagine the TRF cars perform similar, but I've never driven one so that is just a guess.

 

I added the TRF big bore dampers to my Zahhak.  It truly is a night and day difference.  I test it by driving over some semi-rough terrain and the body didn't move at all.  The dampers just soaked up all the movement.

 

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and wheel weights? i know the crawler crowd use them for stability to get the cg lower - but wouldn't it also help to achieve this floaty action? 

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20 minutes ago, MockTurtle said:

and wheel weights? i know the crawler crowd use them for stability to get the cg lower - but wouldn't it also help to achieve this floaty action? 

Unsprung mass is going to make that worse not better. Generally speaking less unsprung mass is where you want to be. With crawlers it’s about getting traction and stability at super low speeds and the suspension layout better suits that application. Fact is your going so slow the detrimental effect of excess unsprung weight doesn’t exist for that application so the advantages of the extra unsprung weight can be found. 

the Traxxas UDR looks the closest to that full scale truck because it most accurately replicates the layout. The combination of weight, travel, properly setup sway bars and sophisticated damping allows suspension to work like it does in that video. 
 

rc lacks many of these elements but the vehicles need to operate in much harder conditions. If we can remove the high speed requirement then we remove the need for stability that firm, heavily damped suspension offers.  

Higher quality rc dampers offer much less bypass which allows you to run much softer damping settings while still maintaining stability. Cheaper shocks tend to have more bypass/flex  in their damping to prevent the shock from leaking under momentary high pressure situations caused by the damping pack down. For that reason they need heavier damping to maintain stability, and low speed movement is muffled. 
 

Tamiya doesn’t really make anything with that particular 4 bar rear With IFS upfront suspension layout. To be honest that arrangement is kinda crappy on anything but scale rc cars, if you wanna go faster than scale speeds, gotta have front and rear independent suspension at the end of the day. 

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1 hour ago, Juggular said:

Does anybody know what is the lightest oil I can buy?  

 

The lightest I've got is Losi 17.5 which is about 180 CST (its hard to find a comparison chart).  Searching around it looks like the lightest Tamiya do is 200CST and thats about where most manufacturers start.  I saw Losi 10WT and AE 7.5WT are in theory 100CST but I have never seen them for sale.

 

RCMart have Mugen 100CST which is probably the lightest - I say probably as CST is an actual measure and Mugen is a good brand so it should be correct.  However, I think some manufacturers make up their own ratings and I don't know anything about Mugen's oils.

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I keep quite a bit of 10Wt oil in stock for various projects where I have access to smaller hole pistons, usually AE brand. The CST of oil weights does alter a little bit from brand to brand. However if I need less than 100cst/10Wt I typically reach for the bottle of 1/1 scale automatic transmission fluid. It’s a viable alternative if you need something super light, that won’t worry your silicon seals. 

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You also have to consider the trade-off for that floaty suspension, namely on a 1:10 car it would make it virtually undriveable. If you watch that 1:1 scale video, watch how much body roll it suffers just by flicking into a slight curve. I suspect that makes it very difficult to handle, as the suspension will compress at every opportunity and the side-to-side wallowing motion will eventually build to the point where it would try and roll you over through a series of left-right-left-right flicks. The size and weight of the car will counteract this to an extent, plus the fact that obstacles, speed and distance are operating at 1:1 scale, so with enough skill the driver can hold that extremely unruly package together.

On a 1:10 car, the counteracting forces are all either different or not there at all. It probably weighs less proportionately than the 1:1 car, and the weight is in different places, with a much lower CoG and no big, heavy engine high up and far forward. The speeds are proportionately MUCH higher, while obstacles and surface imperfections are proportionately much bigger, meaning the suspension is at full travel for much more of the time. Also, we tend to use our cars on much tighter courses than 1:1 scale cars, with corners much closer together. We have to do this, obviously, or the car would go out of range or out of sight. But the upshot is the car will have less time to reset to neutral between corners.

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Until a manufacturer comes out with 1/10 scale dampers with seperate low and high speed compression shims plus low and hi speed rebound circuits with appropriate oil weights you'll never get that amazingly stable body floating appearance. I think it was actually Curnutt who figured out the importance of separating the low speed compression to give the shocks a "platform" to allow the high speed to work independently. This technology is big in the mountain bike world (cancels out peddle "bob") with Fox, Rock Shox, Manitou, Cane Creek etc all having a variation on it. 

I tend to use the lightest oil I can get away with so that the shocks rebound fast enough for the next hit so that they don't pack down. This dependant on the spring weight required to support the vehicle's mass - heavy car, stronger springs so harder oil and vice versa. The car should sag under its on own weight by 10/20% when loaded so that the wheel can dip into small holes whilst the body is level and give that "floaty" effect. 

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14 hours ago, Juls1 said:

won’t worry your silicon seals.

I might have small amount of Dextron III somewhere after replacing 5-6 quarts in our Subaru.  Transmissions must have some heat resistant silicon seals.  But is it plastic safe too?  If it is, cheaper transmission oil is a brilliant idea!  I might have to give it a try!

 

4 hours ago, Grotty Otty said:

I tend to use the lightest oil I can get away with so that the shocks rebound fast enough for the next hit so that they don't pack down.

Me too! 

I try to aim for 1/3 or 1/2 second for rebound.  That does require light oil.  I call it "one-two-three" rule. (I come up with all kinds of self-imposed rules)  I figure saying "one two" takes about 1/3 of a second. "Three" in about 1/2 a second.  

I take one axle off the ground (about 3-4 inches) and I drop it.  From the moment it hits the ground, it should return to upright position by the time I finish saying "three."  If it still osculates like the front of the Grasshopper, it's no good.  If it takes longer, it's also too slow. But slow RC shocks don't return slow at all --because they simply don't compress enough in the first place.  We've all seen how Tamiya cars simply bounce off the floor, not by the springs, but by the tires.  From the moment 2 tires hit the ground, it shouldn't come off of it. The purpose of a suspension is to keep the tires ON the ground as much as possible.  

Your "rule" of 10-20% sag under its own weight is brilliant.  CC01's rear suspension extension kit doesn't allow CC01 to compress more.  It allows to Extend more.  Extra sag helps the tires to stay on the ground.  

Most Tamiya cars have almost no sag under its own weight.  Not just by stronger springs.  Tamiya also uses harder oil with small-holed pistons.  Tires are hard too, so that they can be displayed for months without flat spots developing.  1) hard springs + 2) hard shocks + 3) hard tires = toy rides. Toy rides were okay in 1985. 

But having seen Traxxas UDR, I am thinking it's possible to improve somewhat.  Of course, UDR is Heavy!!  Really floaty suspensions would be hard for 1/10th.  As @Yalson says, it'd be hard to control too.  The suspension travel would have to be twice as long, supported with much weaker springs, sagging 50% down, etc.  There is no room for all that (which is why T-maxx came with 8 softer shocks instead of 4 stronger ones--again, no room).  

What I'm aiming for is something like Matteo's Bigwig and XR311.  Below video shows somewhat floaty suspension, without any oil.  It's a bit too bouncy. Suspension travel isn't much.  But Tamiya's 1977 suspension was supple (you could adjust XR311's suspension hard too).  Somewhere along the line, Tamiya got addicted to hard oil and made suspensions a little too hard, in my opinion.  I think I'll experiment with the lightest oil I can find and see if I can make them more supple.  

 

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13 hours ago, Juggular said:

What I'm aiming for is something like Matteo's Bigwig and XR311

Yup same here, just looks so right. The drop test you mention is spot on. Drop car from a foot or so, suspension should absorb the compression then almost fully extend then settle... And this is why it's all so addictive 😁

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A typical example is the Monster Beetle suspension. No droop by super hard springs in rear, front also too stiff.

On my tuned MB I have Top force rear springs in rear, which is really soft but gives good droop. Combined with tuned CVA s in soft Setup the thing is a new car.

It soaks up bumpy tracks really well, I like to watch it move. About axle weights: I think they really can help. Liked mine in my M06 R on low grip tracks. And actually I Always wondered, why my Tuned MB was less prone to roll Overs compared to the one I built for my nephew, where I copied my Setup. Simple reason: I run full aluminum wheels from RC Lover. And this are noticeably heavier than the std. ones. Would never Change back, due to looks and driving effect. Dampers still can manage the weights of them without having the wheels bouncing around.

CVA Tamiya dampers have so much potential for Tuning, especially when you have very old ones. Aluminum dampers are not always needed, especially when you want to built a "sleeper", which performs better than it Looks.;)

You can check out some Details on my Shocks in 2 of my MB threads, if you are interested:

https://www.tamiyaclub.com/showroom_model.asp?cid=117370&id=34024

https://www.tamiyaclub.com/showroom_model.asp?cid=117764&id=34024

Very cool thread, will follow up  this one...

Kind regards, Matthias

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