4LikesFlat vs Tapered pistons
09-13-2015, 12:55 AM
#16
09-15-2015, 02:30 AM
#17
Tech Apprentice
@icecyc1
Thanks for your answer regarding my Rebound question.
Thanks for your answer regarding my Rebound question.
09-15-2015, 03:05 AM
#18
So really it makes no difference if the taper on the piston is up or down as it just acts like having a thinner piston ?
09-15-2015, 05:37 PM
#19
Contrary to popular belief, yes that is correct. I have not seen any evidence that rebound is different in one direction than the other with a tapered PISTON. It only seems to decrease the overall forces equally in both directions... much like using a thinner shock oil.
09-16-2015, 06:28 PM
#20
This is some great information, do you own the shock dyno? Also good to see the piston kit with the flapper for a valve I want to put in is effective. Would be curious to see a set of Traxxas GTR shocks with and without VDP kit part# 5461 installed.
My results from a shock dyno show very little if any effects from a tapered piston... it depends if it's a tapered piston (no effects) or tapered hole (some effect depending on design).
The concept that is marketed is that the piston provides a different rate of damping in compression as compared to rebound. On a dyno, this would create a higher/lower force on the the top half compared to the bottom half. This was clearly shown with a valved piston. It was also shown with CSI pistons (tapered holes plus tapered piston). It was not as evident with a basic tapered hole piston.
What is consistent, given the same hole size (say 6 x 1.3) for a flat piston, and compared to the "same" (6 x 1.3) tapered hole piston, the tapered hole will have less damping in both compression and rebound than the flat piston (with the same viscosity oil). So, this could appear to give the illusion of "faster" due to the taper, but you really changed the entire shock to behave as if it has lighter oil with no significant C:R ratio effects.
Here's a link to the presentation where I show the results. My signature is the link to the site where the presentation resides for more shock dyno data.
https://drive.google.com/file/d/0B-9...BXMzI4SE0/view
cheers
The concept that is marketed is that the piston provides a different rate of damping in compression as compared to rebound. On a dyno, this would create a higher/lower force on the the top half compared to the bottom half. This was clearly shown with a valved piston. It was also shown with CSI pistons (tapered holes plus tapered piston). It was not as evident with a basic tapered hole piston.
What is consistent, given the same hole size (say 6 x 1.3) for a flat piston, and compared to the "same" (6 x 1.3) tapered hole piston, the tapered hole will have less damping in both compression and rebound than the flat piston (with the same viscosity oil). So, this could appear to give the illusion of "faster" due to the taper, but you really changed the entire shock to behave as if it has lighter oil with no significant C:R ratio effects.
Here's a link to the presentation where I show the results. My signature is the link to the site where the presentation resides for more shock dyno data.
https://drive.google.com/file/d/0B-9...BXMzI4SE0/view
cheers
09-17-2015, 12:43 AM
#21
I'm not sure if anyone else does, but Kyosho makes some pistons that are tapered and the holes are drilled at an angle as well. Any dyno info on those?
09-17-2015, 05:59 PM
#22
I was just informed of those pistons a couple weeks ago, and they really intrigued me, so I ordered a couple 8h1.2mm's. I Hope to test them out this weekend. It's been a few months since I had the dyno going though. I'll be sure to test them with the piston flipped both ways (taper up and taper down). If I do get them tested, I'll mention the findings right away for you guys.
09-19-2015, 09:31 PM
#23
cheers
09-19-2015, 11:27 PM
#24
Great info! The data doesn't lie. It shows no difference at lower/medium piston speeds. I'm curious how the pistons would behave at higher pistons speeds, like when landing. (in pack)
This might show a difference.
This might show a difference.
09-20-2015, 12:53 AM
#25
Just dyno'd these pistons tonight. Zero difference in the Compression:Rebound ratio. As you can see in the plots, they are pretty much symmetrical in compression as they are in rebound. I tested with the taper side down, and the taper side up and it made no difference. (The Flat Down was tested second, so the oil may have warmed up a little, resulting in lower viscosity oil which is why you see a slightly lower force).
cheers
cheers
09-20-2015, 04:26 PM
#26
I think the data presented is only half the data needed to compare with what happens on the track. It's only data for slow and medium shaft velocities. There's no data that shows how the pistons would react when landing. I think those angled holes are made to work differently in pack. (when landing)
09-20-2015, 05:12 PM
#27
I think the data presented is only half the data needed to compare with what happens on the track. It's only data for slow and medium shaft velocities. There's no data that shows how the pistons would react when landing. I think those angled holes are made to work differently in pack. (when landing)
Getting pack results is definitely in order. I just have to figure out a way to build a pack tester that will produce consistent and repeatable results, and a clear way to present that data.
09-20-2015, 05:28 PM
#28
For me the biggest effect in differing shock pistons is the profile of the piston seen from the side.
For example the Kyosho piston is quite thin seen from the side, and allows for lots of blow-by.
HB and Losi pistons are quite thick seen from the side and do not allow for this kind of blow by.
Keep this in mind. It's not usually the taper, it's the thin side surface allowing blow-by.
For example the Kyosho piston is quite thin seen from the side, and allows for lots of blow-by.
HB and Losi pistons are quite thick seen from the side and do not allow for this kind of blow by.
Keep this in mind. It's not usually the taper, it's the thin side surface allowing blow-by.
09-21-2015, 10:49 PM
#29
I think most shock dyno software/fixtures are optimized to collect data when the shocks are not in pack. I don't think the oscillating shock motion simulates what a car landing would see in real life.
If I had to design a fixture to measure pack, I would use a known weight and drop it onto the shock from various known heights. Take high speed samples of the forces on a load cell attached to the shock. This would give us data to plot force vs time from various conditions.
07-30-2021, 04:34 PM
#30
"Hi, everyone! Bob Villa here for This Old Thread!"
This was the best thread I could find on Kyosho's tapered + angled-hole pistons (part# IFW405-128 and IFW405-138), and I wanted to continue that discussion. Certainly much data and track experience has been acquired to date on the benefits (or none) since the last post above. Anyone care to elaborate and discuss, especially the last question/concern about landing a jump?
EDIT #1: Found additional information listed on various sale pages for the tapered pistons:
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EDIT #2: And more food for thought, here's a synopsis of the various Kyosho Inferno variants over the years. What's interesting is that diaphragms are the clear winner of Kyosho's tuning of shocks while angled holes, but we'll call them A-holes, LOL, are the clear losers. Why Mike Cradock decides to tune with A-holes in 2020/2021 is beyond me. Check it out...[S = Straight Holes, A = Angled Holes, F = Front, R = Rear]
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This was the best thread I could find on Kyosho's tapered + angled-hole pistons (part# IFW405-128 and IFW405-138), and I wanted to continue that discussion. Certainly much data and track experience has been acquired to date on the benefits (or none) since the last post above. Anyone care to elaborate and discuss, especially the last question/concern about landing a jump?
EDIT #1: Found additional information listed on various sale pages for the tapered pistons:
----
- AMain & Power Hobby: These pistons deliver smoother function during normal running but provide a greater resistance during landings. Also, FWIW, these pistons were added to AMain in 2009. Just shows how old they are.
- InfernosOnly.com: These [angled holes] are now the stock pistons that come in the MP9 TKI2, WC and TKI3 for the front shocks in the kits. Most racers will change to the 1.3 x 8 hole straight cut pistons because in most cases they work better.
- Mike Cradock Video [unable to post link, but look up "KYOSHO Vlog 09" on YT] About MP10e Improvements: "I'm running 1.2 angled pistons in the front, and 1.3 in the rear; aerated. This seems to give the car a lot more balance and a lot more support at the back end." NOTE: I'm sure the "balance and support in the back end" is most likely derived from the blue (stiff) springs; not the pistons themselves, but someone else weigh in on this.
EDIT #2: And more food for thought, here's a synopsis of the various Kyosho Inferno variants over the years. What's interesting is that diaphragms are the clear winner of Kyosho's tuning of shocks while angled holes, but we'll call them A-holes, LOL, are the clear losers. Why Mike Cradock decides to tune with A-holes in 2020/2021 is beyond me. Check it out...[S = Straight Holes, A = Angled Holes, F = Front, R = Rear]
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- MP9
- 8x1.2mm S @ F & R / Diaphragm
- MP9e
- 8x1.2mm S @ F, 8x1.3mm S @ R / Diaphragm
- MP9 TKI2
- 8x1.2mm A @ F, 8x1.3mm A @ R / Diaphragm
- MP9 TKI3
- 8x1.2mm A @ F, 8x1.3mm A @ R / Diaphragm
- MP9 TKI4
- 5x1.5mm S @ F & R / Diaphragm
- MP9 TKI4 10th Anniversary Edition
- 8x1.3mm S @ F & R / Emulsion
- MP9e TKI4
- 5x1.5mm S @ F & R / Diaphragm
- MP10
- 8x1.3mm S @ F & R / Emulsion
- MP10e
- 5x1.5mm S @ F & R / Diaphragm
- MP10 TKI2
- 5x1.5mm S @ F & R / Diaphragm
Last edited by Ackchyually; 07-30-2021 at 09:52 PM.