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nowinaminute

LONG springs for MINI CVA shocks?

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Does anyone know if Tamiya sell these springs separately?

I got a set of yellow CVA mini for my heavy dump truck but because it was the value set of 4 they only came with the shorter springs which are no good for my truck. I've been using the stock springs from the friction shocks with them but they are too firm and even with 1000cst oil and 1 hole discs the springs are still making things bouncy.

Does anyone know if the longer springs are sold on their own or if there's a kit that includes them as standard so I can see of anyone is selling them off individually?20190713_112533.jpg.7c79baf9a7e1381f2569e7d134066e4b.jpg

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This might help you choose some different springs:

The measurements for the Heavy Dump Truck springs are at the bottom of the table.  The spring rates for.the on-road/rally set or some of the buggy front dampers might help.  I upgraded to CC01 CVA dampers, regular kit springs, and I think 3000 CST oil for some slower movement.  My goal was to slow the movement down to be more scale-realistic, not for better bashing.

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Those long springs in 50519 are REALLY soft. Maybe too soft for heavy dump? According to the dt03 manual the front spring is 9808201. The tt02b front springs 9805947. 53927 set of springs has some stiffer springs options, although not 4 of the same. 

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15 minutes ago, ThunderDragonCy said:

Those long springs in 50519 are REALLY soft.

Yeah the shorter ones aren't much better. I could have used them in theory but the truck just sags right down on them.

I just realised I'm NOT using the stock springs lol. I'm using slightly longer springs because they gave more ground clearance. I think the stock springs might actually be the same length as the shorts springs that come with the CVA set.

I definitely prefer the greater ride height though and it doesn't seem to affect the stability much (not tons to begin with lol)

Only problem is I'm not sure where these springs are from? Maybe cheap HSP shocks? I know some of those need really heavy oil so maybe that's the issue.

I think my best bet might be to just try some even thicker oil to try and reign them in. They are pretty firm so I can go a lot thicker before I risk over damping I think.

I'll try 2000 and let you know. 

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53 minutes ago, speedy_w_beans said:

This might help you choose some different springs:

The measurements for the Heavy Dump Truck springs are at the bottom of the table.  The spring rates for.the on-road/rally set or some of the buggy front dampers might help.  I upgraded to CC01 CVA dampers, regular kit springs, and I think 3000 CST oil for some slower movement.  My goal was to slow the movement down to be more scale-realistic, not for better bashing.

Some great info there. It's a little bit over my head though 😳

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29 minutes ago, ThunderDragonCy said:

May Comical Hornet has pretty stiff springs on its CVA shocks. Part is 9805576

Cool that could be an option if I can't get these ones to behave

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I just noticed these springs I have are progressive as well which explains why the truck is so bouncy when the going gets tough and with jumps etc and that's the main reason I wanted oil shocks! 

The under damping is exaggerated the more they compress.

I'll try thicker oil and see what happens. The only thing I'm worried about now is that to get them damped right for the stiff half might make them over damped for the softer part of the travel.

I'll see how it goes though, I've been driving it around a year anyway so it's not like it's going to make or brake it if there's no difference. If it doesn't give me any joy I'll look into those Comical springs.

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Assuming the short chrome springs you have are the same ones that came with the short CVAs on my TT02D, I find them similar in spring rate to the blue on-road springs from #53333.
Spring Colour (#PartNumber) Spring Rate (lb/in)
Purple (#53636) 22.72
Gray (#53635) 20.91
Blue (#53333) 14.08 <---- similar to short CVA Chrome spring
Yellow (#53333) 13.33
Red (#53333) 11.86

If the short chrome CVA springs don't completely bottom out you can put them in and measure how much they sag when under the weight of the truck, you can estimate how much stiffer the spring needs to be for the vehicle to sit how you want it. For example, if the chrome springs compress by 15mm when the weight of the truck is put onto them, then changing the springs to purple springs will result in (14.08/22.72*15) = 9mm of compression. Installing the plastic clip-on spring collars pre-loads the spring having a similar effect as using springs which are shorter but with a higher spring rate.If you use too many collars on a short spring, the spring will bottom out before the shock does, compromising the suspension travel. Installing a spring which needs to be compressed just to fit it in the short CVA shock is preloading it so it becomes stiffer than when it is uncompressed. I think you will find that once you pre-load those long chrome CVA springs by installing them into the short CVAs, they behave similarly to the short chrome springs. Iirc preloading gives something like an anti-progressive spring rate and should be avoided if possible. 

For optimal realism and traction you want the spring to be compressed to about 30-40% of it's length under the weight of the vehicle, leaving 60-70% of the suspension travel for compression and still allowing the wheel 30-40% droop so it maintains contact with the ground over potholes and such. Tamiya typically seem to run harder springs than this so there is almost no static compression. While this is good to soak up big bumps and land jumps, it's easily lifts wheels off the ground so it tends to skip over rough ground.


 

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2 hours ago, nowinaminute said:

I just noticed these springs I have are progressive as well

Wow, I just noticed something that doesn't exist. Go me.

They are not progressive lol.

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2 hours ago, nbTMM said:

For optimal realism and traction you want the spring to be compressed to about 30-40% of it's length under the weight of the vehicle, leaving 60-70% of the suspension travel for compression and still allowing the wheel 30-40% droop so it maintains contact with the ground over potholes and such.

It turns out I haven't got the stock springs on the truck at the moment but rather ones from some HSP shocks.

They are longer than the short silver springs but still require a preload spacer just to "fill up" the shocks.

I'm not that knowledgeable about suspension but I definitely know what you mean about droop, the stock friction dampers have the truck at max height and are so firm that if you press it down and let go it almost leaves the ground!

The droop with these springs I have is definitely getting in the right ballpark, maybe not perfect but better than out of the box.

This is at rest:

Fxp3yrp.jpg

And this is at full droop:

2Fyif37.jpg

I'm going to try thicker oil to see if I can get the springs under control but if not, maybe I'll try out the short silver springs from the CVA kit again and see if I can space them enough to get the ride height/droop right without limiting the travel.

Talking of springs being too long, check out this Radio Shack truck I've been working on! I guess they designed it to withstand being dropped off the roof by kids but geez! One of those occasions where cutting links off actually makes the suspension softer even though I heard it usually makes it harder?

This one would literally leave the ground of you pressed it down and let go! Zero ability to soak up bumps either, it was like a brick!

received_772745336424593.thumb.jpeg.1571c0c8694392a6866a6875de291b19.jpeg

 

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*Correction: I meant to say that they should compress only about 30-40% under the vehicles weight.

Those springs and spacers you've got on there at the moment look like they are just about perfect! I'd say you just need a lot more damping than the standard 400cst (if i'm not wrong) oil. 2000cst sounds like a good place to start :)

Btw looks like you've got some extreme angles on your driveshafts at full droop. If the shafts run ok with the amount of droop just leave it be. If they clatter and bind up you can install the shorter plastic rod end if it fits which will lower the truck a little and prevent excessive droop of the suspension arms. Alternatively you can put an o-ring or two onto the shock shaft just under the piston to limit the droop and not alter the height of the truck. There's a plastic spacer on the CVA parts tree that is supposed to be used for this (limiting droop if placed inside the shock, or limiting compression if installed on the shaft outside) but it is about 5mm long which will limit far too much and leave you with not much suspension travel (OK for a touring car, maybe less desirable for a dump truck).

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1 hour ago, nbTMM said:

Btw looks like you've got some extreme angles on your driveshafts at full droop. If the shafts run ok with the amount of droop just leave it be.

Thanks for the reassurance about droop!

The drive shafts don't quite rub at full droop. If you take the shocks off, the arms will go even lower and will rub but with the shocks on its just short of doing it. There is a considerable amount of potential extra articulation that the stock setup doesn't take advantage of.

I'll let you guys know how 2000cst works out. 1000 was an improvement but it still doesn't quite have that feel of a cat landing yet.

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Took it to the beach but it was a bit of a disaster lol.

Step screw on the Knuckle fell out AGAIN!! As a consequence the inboard drive cup fell out too, never to be seen again! Probably sand in the gearbox now so that will need a strip down.

I think I'm going to have to get alloy knuckles so I can threadlock the screws in. Nothing I try holds including super glue, wood glue and nail varnish.

The pin screws kept backing out on the suspension arms too.

Oh and a dog ran in front of it so I had to take evasive action into my own shin.

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9 hours ago, nowinaminute said:

Step screw on the Knuckle fell out AGAIN!! As a consequence the inboard drive cup fell out too, never to be seen again! Probably sand in the gearbox now so that will need a strip down.

Before you get too far on buying aluminium bits, my rescue of an over drilled part on my Comical Hornet might help. I drilled out the hole for the step screw to 3mm getting a biy punchy cleanibg out holes in my new c hubs. To sort it i put one of the top hat brass bushings out of the cva shock kits through the upper arm and them put a longer mqchine screw through the whole thing and tightened a locknut down on the other side. Completely solid and shouldn't come undone. 

I believe there is a GF01 Low friction shaft set to replace the step screws. 

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7 minutes ago, ThunderDragonCy said:

GF01 Low friction shaft set to replace the step screws. 

I have a TL-01 set on hand so I think I'm going to use those apart from the u shaped part for the inner front arms because the TL-01 set doesn't have the metal brace so I might leave that part as is. That should sort the lower arms out.

I had the issue with the screws for the upper links falling out too but I already dealt with that last year, 3racing make longer step screws with a machine thread on the end so you can put lock nuts on the other side.

http://www.rcmart.com/3racing-step-screw-heavy-duty-tt01-tt0110hd-p-22708.html?cPath=595_744_708

It's the screws in the uprights I can't seem to stop coming out. Happens with my TL-01b and WR01 too.

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18 minutes ago, nowinaminute said:

I have a TL-01 set on hand so I think I'm going to use those apart from the u shaped part for the inner front arms because the TL-01 set doesn't have the metal brace so I might leave that part as is. That should sort the lower arms out.

I had the issue with the screws for the upper links falling out too but I already dealt with that last year, 3racing make longer step screws with a machine thread on the end so you can put lock nuts on the other side.

http://www.rcmart.com/3racing-step-screw-heavy-duty-tt01-tt0110hd-p-22708.html?cPath=595_744_708

It's the screws in the uprights I can't seem to stop coming out. Happens with my TL-01b and WR01 too.

Ahhhhh, the kingpins? The big stepscrews on the steering axis? Can't help there. Never managed to completely lose one but they have backed out on various cars. I guess alloy knuckles would fix it because the threadlock would work properly. Given it shares parts wuth the M05, would the M05 low friction kingpins fit? Maybe reducing the friction would stop them backing out? 

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