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Yokomo YRX12

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Old 06-09-2016, 09:47 AM
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Originally Posted by aracefan View Post
Thanks for posting those shots, Mr. Smith!!

Does the front suspension look to have more travel? It kinda looks as though there is an adjustment nut below the spring. . . may be just a retainer nut "for" the spring, and not an actual adjustment.

Anyway, car looks way nice!
I had the same questions before I built the kit. That adjustment nut is actually how you adjust the spring tension/weight. There is a set up sheet available you can find online that suggests the starting point for that setting which is 3.7 mm, so by tightening that nut into the plastic end you shorten it and then there's less tension on the spring which softens the rate. Right now I have it set at 3.4 mm which is softer. Smaller distance = softer. On the other end of that shock post you can put silicone inside that sliding tube (for lack of a better term) for dampening. The kit comes with 30,000. This design works incredibly well actually. I hope this helps.
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Old 06-09-2016, 09:48 AM
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Here's the base setup sheet.
Attached Files
File Type: pdf
basic_setup_stock.pdf (141.3 KB, 133 views)
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Old 06-09-2016, 09:49 AM
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In other words, they forgot to add droop screws. Hehe
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Old 06-09-2016, 09:52 AM
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I'm not sure about the spring weight thingy as they sell optional springs for the frontend. But then again I could be wrong. I'll get to see one up close soon so maybe I can check it out.
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Old 06-09-2016, 09:57 AM
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I had some photoshop fun... maybe this helps also. The 2nd pic are the actual push rods...
Attached Thumbnails Yokomo YRX12-20160603_150726.jpg   Yokomo YRX12-push-rod.jpg  
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Old 06-09-2016, 11:00 AM
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Originally Posted by BardSmith View Post
I had the same questions before I built the kit. That adjustment nut is actually how you adjust the spring tension/weight. There is a set up sheet available you can find online that suggests the starting point for that setting which is 3.7 mm, so by tightening that nut into the plastic end you shorten it and then there's less tension on the spring which softens the rate. Right now I have it set at 3.4 mm which is softer. Smaller distance = softer. On the other end of that shock post you can put silicone inside that sliding tube (for lack of a better term) for dampening. The kit comes with 30,000. This design works incredibly well actually. I hope this helps.
Originally Posted by JimmyMac View Post
In other words, they forgot to add droop screws. Hehe
Originally Posted by BardSmith View Post
I had some photoshop fun... maybe this helps also. The 2nd pic are the actual push rods...
Thanks for the explanation, Bard, as that's what it looked like. Very innovative, I like it.

And yes Jimmy - kinda what I thought too. haha!!
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Old 06-09-2016, 12:03 PM
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Preload on the spring doesn't affect the spring rate - unless the spring is progressive. I haven't been hands-on with one of these yet, but it looks like you are just changing droop (preload) and maybe a bit of ride height/roll center.
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Old 06-09-2016, 12:12 PM
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Originally Posted by LloydLoar View Post
Preload on the spring doesn't affect the spring rate - unless the spring is progressive. I haven't been hands-on with one of these yet, but it looks like you are just changing droop (preload) and maybe a bit of ride height/roll center.
I may have used the wrong terminology I suppose.
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Old 06-09-2016, 12:43 PM
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Originally Posted by BardSmith View Post
I may have used the wrong terminology I suppose.
Maybe? The takeaway is just that preload doesn't make the spring softer or stiffer. Same thing as spring collars on a sedan or center shock on a 1/12. If the spring is progressive this isn't true, obviously.

Last edited by LloydLoar; 06-09-2016 at 12:58 PM.
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Old 06-09-2016, 03:14 PM
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The lower arm down travel is limited by the arm mount hence you dont need droop screw especially having in mind there is not much space. The droop could be controlled by the length of the pushrods which also influences the ride hight and front roll center. Should you put preload on the front spring, it eliminates any droop. The roll center could be separately adjusted with shims under the inner upper arm hinge. This is much more complex than the kingpin coil design. I am curious how it will work in practice. In principle there is definately one negative of this design - the unsprung mass is probably double that of the kingpin coil design.
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Old 06-09-2016, 05:04 PM
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On the previous edition front end, there was a droop screw in the bottom of each lower frant arm which could be used to restrict how far down the arm would travel. And there were fat allen head aluminum screws that screwed in or out to put more or less tension on the inboard front springs. By adjusting those two items in tandem, it was super easy to set front ride height and also to achieve any droop setting that one might want with the ride height adjustment. IMO that ability was one of the very best features of the previous version's front end. In looking at the online assembly manual, the new kit does not appear to use those way handy droop screws although one of the posted photos clearly shows that the bottom of the new edition chassis plate does have the holes which would allow one to access droop adjuster screws, if only they were there. Also one of the posted photos shows orange ride height shims in place....something that was completely unnecessary on the previous front end. Hmmmmm.
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Old 06-09-2016, 05:56 PM
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Yeah, I'm still trying to figure it out myself by looking at the online manual. Maybe ride height is a combo of the shims under the bulkheads and tension on push rod and droop is push rod tension. I dunno. But I may have a chance to check it out first hand at the track if someone brings the car in this Sunday for me to check out. We shall see..... If I like it, I may get one soon.....
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Old 06-09-2016, 07:51 PM
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Looks to me as if the new front end's threaded pushrod is just going to be Yokomo's new way of adjusting for the length of the front springs and also adjusting for the desired amount of sag or preload on the front springs.....akin to adding or removing shims from the kingpin of a normal front end.....just a quicker and easier way of making that adjustment. It also appears as if the ride height adjustment will once again be done by adding or removing shims from under the bulkhead. And it looks as if maybe the new chassis plate will also accept the previous front end in lieu of the new setup since the holes are there in the new chassis plate for accessing the old droop screws as are the mounting points for the old dual dampeners. The new dampeners (both front and rear) do look pretty sweet.
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Old 06-09-2016, 07:54 PM
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You guys had me believing the yokomo was the car for me... that many smart racers unable to decipher a manual means I'll be leaving that car in Japan
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Old 06-10-2016, 08:35 AM
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Originally Posted by Racermac73 View Post
You guys had me believing the yokomo was the car for me... that many smart racers unable to decipher a manual means I'll be leaving that car in Japan
If it is anything like the previous car, the manual included with the kit is entirely in Japanese. If the (not very) complicated front end and manual are intimidating to you, then yes, probably best to avoid. Shame to hear since Yokomo kits are so nice and I am sure the car is good, but their 1/12 kits always have been almost 'feared' here in the US. People afraid of the front ends, etc.
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