Granpa

Thanks for the heads up. The foam insert the tires come with is much too soft. Just asking for traction rolling problems with those. I'll give these a try with the next set. Yep, I'm lazy also.

Sydewynder

If you have no air in the shock and have only 100% oil, the shock shaft won't move in. The oil is not compressible so when you try to push the shaft there's no place to displace the volume that the shaft occupies. You either need a bladder with air (air compresses) on top or an emulsion shock where air is mixed in with the oil.

I build my shocks like the vid you posted. The shocks work fine with about about 2 mm rebound. As a matter of fact it has suck back. Pull the shaft all the way out and it'll suck back in a little. To get as little rebound as possible, push the shaft all the way in before you put the bladder on. This will displace the most oil and let more oil out as you put the bladder on. This will leave as little "head" pressure to push on the bladder which in turn won't push back as much.

If you want no rebound at all you need to look into T-Shox. It's similar to the side damper on a AE wgt car. The shaft pokes through on both ends of the shock. No air above a bladder pushing back.

monkeyracing

iTrader: (10)

Never said it would work: It's completely impractical and has possibly hilarious consequences. I've always wondered about emulsion dampers. I had some on a short course truck. Bled all the air through the caps a plugged them, but they still worked perfectly. Weird!

Sydewynder

Oh Jim. I never ever said you ever said it would ever work. I know you never ever implied for anyone to ever build their shocks fully under oil....ever.

Maybe you never ever fully bled all the air out of your emulsion shocks. Maybe some of the air is still ever present suspended in the oil and that's why your shocks never hydrolocked.

I'm done confusing myself......

Granpa

No, not really. There's no interest in other types of shocks, just the TRF or the plastic Mini shocks.

My question was if anyone knew of any way to build these shocks as a true zero rebound shock other than drilling a small hole in the plastic end cap. I knew that using conventional methods would not give one. And I did post the reason why it was nearly impossible to build one.

Sorry that point got lost in the conversation.

Sydewynder

The way bladder shocks are designed, I don't believe there is way to achieve true zero rebound. I threw out T-Shox as others might find it useful to know. I know you run TCS and can't use anything other than Tamiya or drill a hole as that is not built per instructions. No hiding the hole under the ballend.

You noticed I quoted Jim only.

Sorry that I was no help.

Granpa

No problemo. At least you agreed with me which to me is a good thing.
This really is merely for academic interest and had no practical application. Some times things like zero rebound etc. get bandied about carelessly.

It can lead to someone trying to build his shocks with zero rebound which, both you and I seem to agree, is nearly impossible if not impossible. Just wanted to save some people a lot of frustration.

monkeyracing

iTrader: (10)

Sorry Sydey, I forgot to use the sarcasm font, but believe me, I was grinning the whole time as I wrote that.

Sydewynder

No need to be sorry monkey. I fully grasp your sarcasm. I've been reading your posts for a good 3 or 4 years. It was my feeble attempt at wit with the never ever post and maybe the last "ever" in the first paragraph that may have caused you to believe that I wasn't laughing the whole time I was writing it. So I appologize for giving you concern. I did start off with "Oh Jim"...

Laguna Bozo

Question to all Mini Tech Masters and Elitists,
Why would one want a shock WITH rebound? Are not shocks meant only to dampen spring oscillations? If one wants more "push-back", wouldn't a stronger spring be indicated? Or are you trying to get some "in-between" springs fine tuning?

ruebiracer

Not sure to answer your question, but that discussion is (again) really interesting in my eyes.
I also thought and tried a lot to understand the effects of "rebound" in a model car the last 2 years. From the beginning in the childhood, I always built my shocks like Tamiya recommends, with the piston rod fully down when putting the shock bladder on and screwing the cap. With this setup, the piston rod moves completely out again, when you push it in. In a real shock this is a bump force (gas spring) working additionally to the steel spring, as you mention. There are multiple theories also for real cars, why you want that more or less or not, this is not important here.
In the model car shocks, I learned from my races over the years, that some people build them with the piston rod moved completely up or just partly up with spacers (like grahoo in his superb videos). When you now push the piston rod completely in, it doesn´t come fully back, you even have to pull it some mm`s out to see the full shock length. I hope I say it right, please correct me, if I´m wrong: this displacement is meant by "built with xx mm rebound".
I also noticed, that this really can affect the handling of the car, although these forces are, as you say, very small compared to the spring you have.
So my theory, which is maybe crap, is that it affects the roll behaviour of the car, when running with not much preload on the springs. So, if you have for example 1mm of "play" in full length of the shock, where the spring does not work, 2mm of rebound will stop the piston rod going in the full length of the shock, whereas a manual build shock will go to full length, and has to be compressed by the car 1mm, before the spring is in contact and working again. So my guess is, that this reduces the roll angle during cornering compared to a car with the same springs.
Hope I could explain my thought, now I´m open for your input or critics.


Br,
Matthias

Granpa

You're a much braver man than I. This is a pretty complicated issue and I'd agree with much of what you've posted. But, I'm going to sit this one out. A brave effort which I applaud you for.

ruebiracer

Thank you Bob,
I just thought, why not also think about the effects, as a lot was already explained on rebound now.
Anyway, I´m ready to take the punishment for it.

Sydewynder

C'mooon Granpa! You know you want to! You got that nagging itch you gotta scratch!!

Granpa

Nope, not this time. I'm far smarter than you think. Falstaff had it right. Discretion is the better part of valor. Poor Mathias made a pretty good stab at it, but I fear he's in for it. Too many variables to make a cogent and/or concise argument. You're not sucking me into this one.

This is one of those situations where you can be wrong and right at the same time.