Discussion in 'Sim Racing Hardware' started by Hristo Milushev, Nov 12, 2014.
Exact size - 25mm х 2mm (inner diameter and thickness)
That is a great and very inexpensive mod. And don't worry about your English. I understood everything you said.
I have a question, could you share the dimensions of the screw that you used as well as the O-ring?
I did this to some success and still need to improve on it.
The screw I did not recall the size, I just looked in my bolt jar and found one that thread was a wee bit bigger than the hole , the shaft a bit smaller.
O-ring this was a bit of a hit or miss! More miss than hit. I still have the "miss" installed and can not tell the size unless I take it out. A friend gave me gave me some rings of varying radius and sections. I landed up with them either too big in section (did not fit in the groove on the G27 pedal male cylinder) or too small a overall diameter.
I landed up with one that had a section that was close to the correct size but the diameter was too small but when the ring was stretched to fit around and in the grove the section became too small. A hack fix was to take some plumber's white teflon tape (really thin stuff) and built up the groove a little. After putting it all back together I realised I had put too much teflon tape in the groove so the ring has a little too much friction on the female cylinder and is a wee bit sluggish on the release. Still got to find the right diameter and section. I must admit it feels better.
Some other thoughts:
The pedal still bottoms out but only close to the max compression
Some solutions I am thinking of
need a stronger spring to overcome the ring friction I have a feeling the less friction the higher chance of the air escaping.
a more complicated idea is to fix a bicycle tyre tube valve into the cylinder to be able to pump more air into the cylinder and then we could adjust to suit the pressure required, might need a reservoir for this.
But first I think I need the correct ring
One thing to keep in mind is that the brake does take alot of abuse. Whether or not we think so because the motion is so linear. But the friction you mention is in essence the enemy. And then, without the needed friction, we do not get the feeling we are looking for in the brake. (That hydraulic feel). So no matter what ring you place in the groove or how you build out the groove, we are faced with the components at some time giving into some wear. Then the feeling is not the same as in the beginning.
But all things considered, yours is perhaps the least expensive route. Here's why. The screw is a one time piece and will not need replacing unless you wear down the plastic around it inside the cylinder. The o-rings can be bought in quantity up to about 100 pieces once you find the right size and diameter for super cheap, and the internal spring, once you have it (I'd suggest progressive not linear), you will not have to replace this either. (Might want to take a look at an engine valve spring. Might just be what you are looking for. More so from an american engine like a Chevy, Chrysler or Ford. These tend to be beefier and heavier.
I'd be interested to see how you progress.
I forgot to mention that I do indeed have a stronger progressive spring the "GTEYE" it was the first mod I did and it was a great improvement to the original it is still in the brake and the sealed chamber has improved on top of the spring
The mod is probably the cheapest G27 pedal mod in the whole internet, on par with the rubber string sequential shifter. Outstanding little idea.
As in the video, vacuum grease should prevent it getting stuck and air leakage.
I don't think the non-linear spring adds much (anything?) to this mod. I have the GTEYE myself and I can hardly feel the non-linearity. The volume-pressure relationship is already non-linear (approximately an adiabatic compression), much more than the spring.
One way to increase the maximum force (and also the non-linearity) is to eliminate dead-volume so the volume ratio final/initial is decreased. For example place a longer screw that occupies the center part of the bottom cylinder. Or put washers under the screw, you pre-load the spring at the same time that you reduce the volume, that would increase both initial and final pressure.
Approximate example, if the volume extended is two cylinders, the volume compressed is one cylinder, and the pressure extended is 1 atmosphere, final pressure is 2.6 atm. If instead we place something occupying part of the bottom cylinder, say, 25% of it, the volume extended is 1.75 cylinders, the volume compressed is 0.75 cylinders, the final pressure is 3.3 atm, almost 30% more.
The limit is how much pressure the o-ring can hold without leakage. Otherwise you could make the final force as hard as you want purely by gas compression.
P.S. who would have said, I finally did find a home application of thermodynamics, took me almost 15 years!
I bought a Nixim spring and buffer but it hasn't arrived yet, so in the meantime I found some o'rings and decided to try the mod. I followed your tip and filled a big volume of the cylinders with playdough, because it's ease to fill the smaller spaces with it but it isn't a liquid, which could cause problems if some leakage occurred. It's very good, even with the standard brake spring it's very progressive and heavy at the end, it's actually impossible to bottom it out. The one problem I had is, maybe because I couldn't find the right screw and closed the bottom hole with 3M tape, or maybe because my O-Rings are so low quality, I have some air leakage after playing for a while and from time to time I need to disassemble it to fill it with air. It's still a good mod and until my progressive spring arrive I can't play without it anymore. The standard spring is just awful.
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