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BuggyDad

A sloooow XV-01 build

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A question that those with a half decent knowledge of suspension geometry can probably answer in a heartbeat...

Raiding my XV-02 kit for a turnbuckle to replace one I've lost (but already unhappy - rod ends loose, slight bend) on my XV-01 today, I notice in the manual something I don't understand.

The two cars share the same lower arms. Lengths about 43mm F, 49mm R pivot centre to centre.

XV-01 upper arms are a 23mm turnbuckle set to 5mm between the rod ends, which equates to pivot centre to centre about 35mm on the back. Front I think ends up about the same (longer, but angled). So, upper arms much shorter than lower, and this is much more pronounced rear than front. This will make negative camber increase as the suspension compresses. I get that and presume the reason why is to maintain or increase outside wheel grip in roll in a turn. On the bench it seems to maintain outside wheel angle relative to the ground, broadly speaking, when you simulate a turn.

XV-02 upper arms, however, are 32mm turnbuckles set to 16mm gap, so 11mm longer, which seems to me a huge difference. So rear upper and lower arms are pretty much the same length, front uppers are longer than lowers if I have this right. This seems weird to me.

Then there's the steering. Tie rods on the 01 are long - 42mm turnbuckles, arms end up c. 55mm. Long, but angled up, end result appears to be no visible toe change on compression until the extreme, when they go to increasing toe in a little. Seems sensible. On the 02 they're the shortest 23mm turnbuckles ending up around 36mm eye to eye. Very short compared with the arms. Not built yet so don't know how they angle up/down. But won't they toe out on compression? Is that desirable?

No criticism here, all just questions in the name of learning. Sorry so long winded. Mark Twain: "I didn't have time to write a short letter, so I wrote a long one instead." Me: "I didn't have the brains to write a short question, so I wrote a long one instead." 

Also a discovery: the TT-02B turnbuckle set has in it 3 of each of 23mm and 32mm. A near ideal spares package for owners (well, abusers) of both XV chassis. 

And another point I noted: XV-02 rod ends grey vs XV-01 black. Grey ones are perhaps the low friction ones. They may be harder, not sure, but harder plastic would I think be good here. Next time I need more I think I'll aim for those. 

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Just trying to think, but my touring cars generally have slightly longer rear top arms compared to front, but that is very different. Camber gain is a function of arm angle as well as length though. Also, with caster, the fronts get camber change through steering too. 

As for steering links, the shorter xv02 can be OK if the inner pivot is roughly in line with the inner lower arm pivot and roughly the same angle. That way, despite being shorter it follows the same arc so doesn't bump steer. 

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7 hours ago, BuggyDad said:

Are you running stock springs all round?

Yep. Except for the longer eyelets on the shocks the car is completely build per manual.

7 hours ago, BuggyDad said:

A question - is the stock pinion coated or easy wearing aluminium? 

No clue I'm afraid. Should check. Maybe tomorrow I can get some space cleared on the workbench to take it apart to take a look at the pinion. It's the one that came with the kit so I assume Tamiya alu :wacko:. Will change that when I install the 3000KV brushless system. I know the reputation of Tamiya alu pinions but never experienced any problems as long as I stay with silver can motor.

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21 minutes ago, ThunderDragonCy said:

Just trying to think, but my touring cars generally have slightly longer rear top arms compared to front, but that is very different. Camber gain is a function of arm angle as well as length though. Also, with caster, the fronts get camber change through steering too. 

As for steering links, the shorter xv02 can be OK if the inner pivot is roughly in line with the inner lower arm pivot and roughly the same angle. That way, despite being shorter it follows the same arc so doesn't bump steer. 

Well, I guess I'd better build it and see! Behaviour should be fairly obvious once built I guess. From a glance at the manual I didn't even guess at angles. One possibility is that the long upper arms have a big angle fore/aft, which would simply make them shorter in the arc that counts and eliminate any difference. Another possibility may be that the lower arms at ride height extend downwards (XV-01's are about level), so push out more in the travel - some pics do imply this. I think the 02 is designed with more ground clearance as stock. 

Maybe I will turn this thread into one for both my 01 and 02. 

I'm intrigued that tamiya has made these two cars, both rally, both sharing a lot of parts and geometry, with the 01 still lauded as best in its class at the release of the 02, yet they changed some of these measurements for the 02 by so much. 

It does look like the inner steering pivot will be pretty much in line with the inner suspension pivot. 

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49 minutes ago, Tamiyastef said:

No clue I'm afraid. Should check. Maybe tomorrow I can get some space cleared on the workbench to take it apart to take a look at the pinion. It's the one that came with the kit so I assume Tamiya alu :wacko:. Will change that when I install the 3000KV brushless system. I know the reputation of Tamiya alu pinions but never experienced any problems as long as I stay with silver can motor.

It looks like this:

2023-01-17_10-46-57

I don't see a visible coating but it's machined out for weight saving which my other stock ones aren't, so I wondered whether it's a higher quality part.

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20230118_220058 2023-01-18_09-27-38

Phew. First 4 decals applied. Tough but doable with time. It makes me glad I made this build a challenge to myself to slow down and enjoy the time taken. I won't get back to this now for a week or so, which is perhaps a good thing. I was a bit concerned about the heat and manhandling this new paint has got. 

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Looking perfect. And as far as I could see it's just regular Tamiya alu for the stock pinion but no major wear for now.

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And it's done. 

20230220_212029 20230220_211655 20230220_211543

I think a shell in Martini stripes is a Tamiya rite of passage. 

It's not perfect, but I'm not very experienced and I am happy with the result. I think it's a pretty good stab.

I do have a cockpit to add to it but this is the kit completed so the cockpit is perhaps a project for the more distant future. Also widening the rear track, which I'm not sure is necessary visually although a couple of mm would be an improvement, and I do have the parts. My mini lite wheels have some extra offset and they do work width wise front and back actually. In fact, I might try +2mm hexes without changing any stub axles, but not tonight. 

I love also how the body fits the chassis, it sits on really tight with foam rings on each post, and the lack of overhang front and rear makes it all feel very together. It looks perhaps a little low, but having driven the chassis a fair bit I intend to raise ride height by about 5mm, which is half of what longer eyelets do but which will I think look pretty tidy with these post positions. 

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Congrats the completition. It looks stunning. I see there is a nicer stance with this body compared to mine (which I think must be a Killerbody). Now go enjoy :).

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Thanks all. 

Having done the shell, there are a lot of decals remaining. Most are clearly cockpit related but there's a pair I haven't figured out. Anyone know where these go? 

20230220_220609

 

 

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I put some 55mm YR "big bore go" shocks I forgot I had on my XV-01 in an effort to roadify it for next month's postal racing. It's a shot in dark with settings (I went 800 cst & medium springs front, 500 & soft rear, 4 hole pistons all round) rear feels quite nice, front a bit bouncy like it's bouncing on the tyres a little, but it seems to drive quite well, and it's still got very-worn-at-the-edges rally blocks on (will get some road wheels/tyres but not got around to that yet). Aim was for more precise cornering really, not full touring car but decent on tarmac. I've no idea whether I've achieved that but it does seem more composed when going flat out. Which of course it'll never do in a postal race!

8mm ride height so a sort of middle ground between TC and something that can take a bit more of a range of surfaces. And it's got rid of the body roll (which is cool for the rally setup but is a bit wrong to me on a short tight tarmac circuit).

I had thought I'd have 2 sets of shocks so I can swap between this idea and the old rally setup at will. I still can but the YR shocks take bigger ball studs so they have to change too, so it's not quite so simple.

Still should refine shock settings though. I suspect it ought to be a little softer at the front, but it turns OK so I'm not sure. Ideally I'll run some 5 minute sessions like this (but with road tyres) and then try a change if I have time, to see if whatever change improves my count. Proper science like! 

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3 hours ago, ThunderDragonCy said:

Top puzzling! Would recommended the Ride cut slicks for general road use. They come on a couple of nice looking wheel options. 

Ah yes. Thanks. They are the plan, on your previous recommendation, I just haven't got round to shopping yet.

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On 2/21/2023 at 4:35 AM, BuggyDad said:

Anyone know where these go? 

20230220_220609

 

 

I was curious about this sticker too.   Haven't figured it our yet either.   I test fitted it around one of the helmets and the seat back but neither seem to be a perfect fit.  

If you figure it out, let me know!  

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1 hour ago, OnTheTrail said:

I was curious about this sticker too.   Haven't figured it our yet either.   I test fitted it around one of the helmets and the seat back but neither seem to be a perfect fit.  

If you figure it out, let me know!  

I offered them up around the cockpit in various places but I couldn't work it out. There are two of them, so I figured probably a matching left and right position somewhere. 

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Yeah, i have the same shell on a TT02 and there was a load of stickers that just didn't seem to referenced in the manual, as you say, some are for a cockpit, but there were quite a few i couldn't figure out.

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They're for the back of the seats in the cockpit set, they simply wrap around. You can just make them out here in the image.

Many of the odd little stickers on that sheet still remain from the first release that came with the cockpit set, if I remember correctly. spacer.png

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On 3/30/2023 at 5:26 PM, Joe Bo said:

They're for the back of the seats in the cockpit set, they simply wrap around. You can just make them out here in the image.

Many of the odd little stickers on that sheet still remain from the first release that came with the cockpit set, if I remember correctly. spacer.png

Ah ha! Only just clocked this post. Thank you! 

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Gotta pop this here, just because it's my best RC pic

20230221_210912

Love this car, so having moved it to the tarmac dark side only recently, I've bought another kit. The old one can return to it's spiritual home in rally, not sure whether long or short damper spec but I will give long damper a try. 

The new one can take over the road job. 

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Does anyone have information on what different parts were used when Tamiya released a TC version of the XV-01? I have seen it said on here that they did that but I haven't tracked any info down on it yet. 

I would be interested to learn from that before I build my new XV-01 kit for the road. The only changes I've used so far are shocks and wheels, and I'll fit 0.4 mod spur and pinion for quietness too, but there may be opportunity to change more besides. 

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7 hours ago, BuggyDad said:

Does anyone have information on what different parts were used when Tamiya released a TC version of the XV-01? I have seen it said on here that they did that but I haven't tracked any info down on it yet. 

I would be interested to learn from that before I build my new XV-01 kit for the road. The only changes I've used so far are shocks and wheels, and I'll fit 0.4 mod spur and pinion for quietness too, but there may be opportunity to change more besides. 

https://www.tamiya.com/english/rc/rcmanual/58558.pdf

Looks like it uses the TB03 style suspension blocks and reversible suspension from the TB03/FF03 era cars. The TT02SR still uses that. 

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34 minutes ago, ThunderDragonCy said:

https://www.tamiya.com/english/rc/rcmanual/58558.pdf

Looks like it uses the TB03 style suspension blocks and reversible suspension from the TB03/FF03 era cars. The TT02SR still uses that. 

Ah ha. Good find! 

Locked front diff too and Ally shocks. Was thinking to use heavy front diff oil, for similar driving effect. I shall have to compare manuals more closely to try to understand precisely what the suspension differences between this set of parts and the stock XV-01 setup are for. What is it, I wonder, about these arms and hubs that makes them better for the on road application than the XV-01 ones? They fit between same suspension mounts and same wheel positions so do they change other geometry/angles like caster, rear toe and anti-squat? 

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11 hours ago, BuggyDad said:

Ah ha. Good find! 

Locked front diff too and Ally shocks. Was thinking to use heavy front diff oil, for similar driving effect. I shall have to compare manuals more closely to try to understand precisely what the suspension differences between this set of parts and the stock XV-01 setup are for. What is it, I wonder, about these arms and hubs that makes them better for the on road application than the XV-01 ones? They fit between same suspension mounts and same wheel positions so do they change other geometry/angles like caster, rear toe and anti-squat? 

I doubt they change any of the fundamentals like that, although by moving to the trad TB03 blocks you have options (including the latest adjustable blocks) to adjust toe and track width much more than the XV01 parts. The main thing is the much longer arms. They have way less scope for suspension movement (hence why your XV01 has short arms and buggy style uprights), but the longer arms give less roll centre change through the travel which apparently makes the car more consistent. Can't say I'm good enough to notice. My 'short arm' FF01 is delightful. I'm only doing the long arm project for ****s and giggles. 

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On 5/19/2023 at 11:06 AM, ThunderDragonCy said:

I doubt they change any of the fundamentals like that, although by moving to the trad TB03 blocks you have options (including the latest adjustable blocks) to adjust toe and track width much more than the XV01 parts. The main thing is the much longer arms. They have way less scope for suspension movement (hence why your XV01 has short arms and buggy style uprights), but the longer arms give less roll centre change through the travel which apparently makes the car more consistent. Can't say I'm good enough to notice. My 'short arm' FF01 is delightful. I'm only doing the long arm project for ****s and giggles. 

That roll centre stuff is above my pay grade at the mo. It might be interesting though to build it stock(ish), run it for a good while and then later to change these parts and learn about what they do in the absence of other change. One for the future list of many maybes. 

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