Speedy's RM01 Lancia Stratos Build Thread

[ALEXKYRIAK 1046]

I have to second that. This build thread is seriously impressive. The attention to detail and creativity is on another level. Great job mate.

Particularly impressed with the god-like ability to magic up 3d parts on a whim  

 

[Yalson 514]

There is indeed some amazing stuff going on here. Not sure if you're aware that the Stratos had an on-road endurance racing history as well as its more famous rallying past, but either way I'll just leave this here. The Lancia Stratos Turbo Group 5 racer:

[speedy_w_beans 4272]

Latest update:

The cold and rainy weather finally broke late last week, and I spent a few days outside working on house and car tasks.  In the evenings I took the RM01 out to test in the driveway and tinker with its setup.

To address the question about the battery's size and run time -- this looks like zero problem at all.  Starting with just a storage charge (3.8V), I've been able to run the car about 5-7 minutes and only needed to replenish about 500 mAh.  So, with a fully charged battery I would expect 3x as much run time, maybe 15-20 minutes as originally guessed.  The overall light weight and the modest power requirements of the 380 motor work perfectly with this small battery.

I didn't do any specific preparation for the first test run other than to make sure the steering trim was good.  It was a mixed bag of impressions initially.  Acceleration and power were more than enough, both in a straight line and turns.  Braking was weak, but I considered it a good thing since RWD pan cars only have rear braking anyhow.  There was more than enough steering, and it was easy (too easy) to spin the car out with the throttle at extreme steering angles.  The main suspension seemed too stiff; the rear of the car seemed to 'buck' a lot over concrete joints and under heavy throttle in turns.  It was almost as if the tires were the only suspension in the rear.  My overall thought was the car was challenging to drive and not particularly fun, even if it had plenty of power.

I attacked the pitch and roll dampers first because it seemed like the 'bucking' of the chassis could be traced to the thickness of the antiwear grease used during assembly.  I replaced the grease with the same Oatey silicone faucet and valve grease used in the ball diff, and there was now very little damper resistance at all.  A second test run turned out to be better; the chassis and especially the rear pod were much more stable now.  I couldn't see any visible bouncing at this point.  Power was still good, braking was still weak, steering was still tight, but spinning out in a turn while adding throttle was still touchy to me.  Although, with more driving I was getting better and adjusting style somewhat to compensate.

For the third attempt I replaced the front kingpin springs, changing from gold (medium) to black (hard).  The idea was to stiffen the front suspension to fight oversteer.  To a certain extent this turned out to be true.  Actually, what it seemed to do was introduce more off-power/coasting understeer, yet I could still overpower the car in a tight turn and spin out if I wasn't careful.  Subjectively this was worse -- I'd rather have less understeer while coasting and work on the oversteer a different way.

I swapped the black (hard) front springs to silver (soft) for the fourth drive.  I seemed to get my steering back while coasting, but it didn't seem like much more than what the gold (medium) springs provided.  So at this point I have silver springs installed, but for outdoor bashing either silver or gold seem to work equally well.  Swapping these springs in and out of the front suspension was the perfect opportunity to take some measurements:

I have the RM01 pitch spring set and roll spring set on order to experiment with those options as well later this week.

Not getting any easy/quick resolution to how sensitive the car is to throttle input in tighter turns and full throttle acceleration in a straight line, I broke out the setup tools to measure the car and make adjustments.  The goal here was to verify ride height, check weight distribution, and check for tweak affecting balance.

Ride height turned out to be uniform, just as I had hoped with flipping the axle spacers in the rear pod and adding the washers under the front uprights.  Typical racing setups might have a ride height of 5-6 mm; my chassis rides a little higher (10 mm) on purpose to help it clear sticks and pebbles.  I'm sure this contributes to some of the handling issues, but it's important to me to clear typical street debris.  Anyhow, ride height is what it is at the moment.

When I first placed the car on a set of scales I was surprised to see nearly a 30 gram difference from side to side both front and back of the car; visually the car looks pretty balanced and I had set the roll spring adjustments exactly to the manual settings.  However, I backed off the roll spring tension completely to let the front end and rear float relative to each other, and it became clear the roll springs had introduced some artificial tweak in the setup.  With the springs backed off, I could see the front end only had a gram of difference from side to side, and the rear only had 7 grams of difference side to side.

Experimenting with some wheel weights from the local automotive supply store and carefully adjusting the roll springs, I was able to get the corner weights somewhat closer.

Result:  a 2-gram difference up front and a half a gram difference in the rear.  I cycled the suspension several times and checked the resting readings; this was about as good as I could make the chassis.

The side-to-side balance is good.  I wish there was more weight in the rear to help with traction.  The total weight has gone up thanks to the front bumper assembly and the balance weights.

The last setup item I looked at was steering throw.  I had read another person's comment that 20 degrees of steering throw is about right for a 1/12 pan car, and I knew my car had more than that available.  In fact, I had already dialed back the steering end points on the radio from 100% to 80% initially.  Throwing the chassis on the setup station tools, the front end has about 2 degrees of camber and 4 degrees of caster.  The rear, of course, has zero camber and zero toe since it is a solid axle.  With 80% EPA I was getting about +/-30 degrees of steering throw, so I dialed back the EPA until I was getting about +/-20 degrees of throw.  This turned out to be 53% EPA.

With this measured and adjusted chassis I found the fifth driving experience to be...  about the same as the fourth drive!  The turning radius was larger, of course, and I could marginally apply more throttle because the car was steering less, but there was no dramatic breakthrough from making these changes.  However, as I mentioned earlier, my driving style continues to evolve knowing what conditions the car is most sensitive to.  In a lot of ways it's like my driving impressions of the F103GT, but the "RM01GT" is definitely more sensitive to throttle.

So where to go from here?

• The rear tires are extremely flat across the tread width.  I was wondering if all of the tread was actually making contact with the concrete and contributing to grip.  One thought was to stuff more foam into the tires to make the tread bulge just a little (maybe 0.5 mm), but then if the majority of the grip is coming from the tread near the sidewalls, I would expect faster wear there.  So far the tires are wearing very evenly.  At first glance this doesn't seem like a good option.
• I was thinking about loosening the rear diff nut some, but the diff is already in the sweet spot between tight and loose.  Holding both tires I can just barely make the spur gear move while pushing on it with my thumb.  Loosening the diff more would mean increased slippage, which I don't want.  The diff is still butter-smooth and it would be great to keep it that way.
• I could change the motor pinion from 14T to 16T or even 18T to reduce the motor's effective torque and gain some top speed.  I'm 50/50 on this one... I'm enjoying the good acceleration and more than adequate top speeds already, and the motor and electronics are barely heating up.  A larger pinion could help with traction, but it could also generate more heat and hurt runtimes a little.
• The back of the motor pod has some spare mounting holes; it would be easy enough to design a bracket and hang some extra weight out back.  A little extra mass, like 40-60 grams, might generate more rear traction, but it adds to the unsprung mass.  Not sure how it might affect the main chassis plate and the pitch spring/damper.  Another one where I'm 50/50...
• Try some different pitch damper springs and greases.  Too stiff seems like a problem; is it possible to have too soft a spring?  Maybe a softer spring would pitch more weight to the back under acceleration and help traction...  Springs are arriving later this week.
• The other thing I've noticed is under hard acceleration the motor pod reacts by trying to rotate backwards; this unloads the spring and potentially locks the pod against the pivot ball bump stop.  Maybe some clips so the pitch damper works both under compression and tension would change how the rear pod works.  It's funny how the rear pod behaves similarly to the gearboxes on the Grasshopper, Lunch Box, and Mad Bull.
• Maybe add a gyro before the splitter lead and use it to control both servos.

Honestly, based on the way the car is driving right now I tend to think there is a surplus of motor power and a deficit of traction due to the lack of rear weight.  There's only so much stiction between the Mini Cooper Racing tires and the concrete with 370 grams in the rear.  My thinking at the moment is to try a softer pitch spring and then a gyro.

 

[ThunderDragonCy 7876]

Is there lot stickier rear tyre option? Or are you keen to keen the road look tyres? Some racing slicks would stick it down would they not? If I have learnt anything from trying to tune my own project recently is that tyres are still ground zero for tuning grip. I know you know this 😉

[speedy_w_beans 4272]

52 minutes ago, ThunderDragonCy said:

Is there lot stickier rear tyre option? Or are you keen to keen the road look tyres? Some racing slicks would stick it down would they not? If I have learnt anything from trying to tune my own project recently is that tyres are still ground zero for tuning grip. I know you know this 😉

I think in my first or second test drive I swapped in a set of Tamiya 60D Type A slicks in place of the Mini Cooper Racing tires, and they didn't make a difference as far as I could tell.  It would have been a good option if it worked since the tire diameter is the same.  I do have a package of Sweep Racing MN25s, but the diameter is closer to the foam tire diameters -- too small.  I've been eyeballing Kawada's TUM-03W tires, which are extra wide.  I think it was @Raman36 who mentioned at one point he was able to get his M06 usable on a track with extra-wide rear tires.  However, it's not clear to me the TUM-03Ws are 60D -- they might be smaller.  I have plenty of room with the axle spacers to run wider rear tires.

The diameter is important to maintain the proportions with the shell.  Sticky, wide, or sticky and wide would be great to improve rear traction.  Barring that I'll play with the suspension and try a gyro to get the best I can with what I have.

 

[_oliK 108]

17 hours ago, speedy_w_beans said:

 

• Try some different pitch damper springs and greases.  Too stiff seems like a problem; is it possible to have too soft a spring?  Yeah when it scrapes... Most racing springs are stiff only in or order to keep up with body roll under fast cornering/heavy braking. But softening the rear as much as possible makes total sense. Maybe a softer spring would pitch more weight to the back under acceleration and help traction Plus a smoother ride. I can't imagine pan cars built for carpet having springs that can cope with bumpy asphalt, so changing that is be a good idea...  Springs are arriving later this week.
• The other thing I've noticed is under hard acceleration the motor pod reacts by trying to rotate backwards; this unloads the spring and potentially locks the pod against the pivot ball bump stop.  Maybe some clips so the pitch damper works both under compression and tension would change how the rear pod works.  It's funny how the rear pod behaves similarly to the gearboxes on the Grasshopper, Lunch Box, and Mad Bull. Anything that resembles a Grasshopper is generally worth changing! 
• Maybe add a gyro before the splitter lead and use it to control both servos. Mmmh don't know if that works. If you look at gyros in drift cars, you can still pitch the car sideways and then they start countersteering, because they only react to acceleration changes once they're happening. It might be worth a shot, though for me it'd be a last resort. Then again, I have never tried a gyro on a grip car.

 

[speedy_w_beans 4272]

A few quick things:

1)  Pitch and roll springs are showing up tomorrow afternoon, so I should have a chance to try different springs later in the day.

2)  I looked into stickier tires beyond 60D Reinforced Type As and Sweep MN25s, which I have in my parts box.  Of course Tamiya has their 60D M-grip and S-grip tires, but they also have mini Super Slicks.  The Super Slicks look almost the same as the Super Slicks that come on the F103GT.  After looking around on various retailers' sites, I ordered a set of Pit Shimizu PS-0450 Super Soft Slick 60s.  It'll probably take another 5-6 days before those show up for testing, but I'm hopeful as one reviewer suggested they helped his M06 grip like crazy.

3)  I tried a gyro from my parts box, basically a re-branded SkyRC GC301 (TrackStar Gyro vs. SkyRC Gyro).  The installation turned out to be super easy; I just taped it on top of the receiver, moved the servo splitter lead, and inserted the jumper lead between the receiver and gyro.

I didn't bother with the programmable gain feature using channel 3 of the radio; instead I just used a small screwdriver with the gain adjustment on the face of the gyro.

The result was meaningfully better!  I had to work with the gain setting a little to find the sweet spot, but the difference between zero gain / no gyro and about two-thirds of full gain was night and day.  Full 100% gain led to some steering instability; the front wheels would hunt from side to side thanks to the delay of the servos themselves, but two-thirds was a good compromise between stability and responsiveness.

I suppose the overall sensation is I doubled or tripled the grip of the rear end just with including a gyro in the setup.  The reality is the tires were probably still slipping in some turns, but the gyro would sense and correct for it by countersteering faster than I could manually.

So, I'm hopeful that with the Pit Shimizu super soft tires and the gyro this chassis will really stick quite nicely to the driveway concrete and street asphalt.

[_oliK 108]

Wow I didn't think the gyro would work that well! Congratulations!

 

[Fabia130vRS 2098]

Long text, very well explained.

 

A gyro is worth every penny, I am using the MST LSD 2.0 in my f103 and results are great on minimum sensitivity.

[Kevin_Mc 411]

I found the same with the gyro on my M04-XL - full gain and it was twitchy, no gyro and it was a handful. About 2/3s dialled in and it was quick enough to catch a slide without being all over the place in a straight line. 

[speedy_w_beans 4272]

It's going to rain on Saturday, and then I get ~3 hour window to paint on Sunday with 62F / 17C temperatures.  This could be the last opportunity to paint outside for the rest of 2018.

So, two questions:

1.  Red, yellow, or blue?
2.  Monochromatic, or black splitter/wing/duck tail?

[Kevin_Mc 411]

It has to be red with black touches Paul!

[Fabia130vRS 2098]

Red with black

[ruebiracer 1046]

Really like this build very much Speedy! Great, that you also show your setup process in detail, very informative! Regarding your rear traction, I´m quite sure you choose the wrong rera tire, as I know the 60D wheels quite well since 1997. Also, your car is very light compared to even the lightest m-Chassis I guess. So pull on the 60D S-grip compound on the rear. This gives you the same look as with the std. radials, but far more grip even on could weather and rain. S-Grips are our superior rain tire in our M-Chassis championship, by the way. Pit Shimizu are also great tires, but the 60D can be twitchy, too. the 55d are probably the best for grip with the low side profile.  So if you ran on the open streets with some dirt on, I think the s-grips are your choice, also because of the thread.

All the best for painting, and as this machine is from Italy, I voted for red / black ! Wish you the best success for the painting!

Matthias

[ThunderDragonCy 7876]

All those colours look amazing, but can I add that you need to paint the wheels white? The cars on white rims up there look incredible! 

[ALEXKYRIAK 1046]

Eye-popping red, black splitter, gold wheels!  

(although blue with white wheels gets my second place vote).

[_oliK 108]

Tough choice, though I'd say red and black with gold wheels

[Yalson 514]

As far as national racing colours go, you probably know

Red = Italy

Blue = France

But how many people know

Yellow = Belgium?

The Stratos is one of those cars that looks amazing no matter what colour you paint it. If it has to be one of the above, I'd pick Red/Black/Gold, but have you considered painting it white and adding a full Alitalia scheme?

[speedy_w_beans 4272]

Well, I'm committed now...  The splitter, wing, duck tail, and louvers are all painted black.  It was too cold to paint outside, but I was able to prep everything in the house, step into the garage, shoot some black, and come back inside immediately to house temperatures to let the paint cure.  It's not a problem with a simple color like black on a small area, but I wouldn't try this with a metallic or pearl color or a large area.

Tomorrow I'll mask the rear window and shoot some PS-60 Bright Mica Red.

[ruebiracer 1046]

Superb masking work already now!

Can´t wait to see the end result!

[VagabondStarJXF 350]

4 hours ago, speedy_w_beans said:

Nice. Makes me wish I'd done up my rear window louvers in the same colour as my front and rear spoilers. I used a combination of smoke backed with gun metal because I thought that gloss black was a bit too 'strong' against the orange & silver scheme I went for. (Here's a link to my M04S Stratos)

 

 

[speedy_w_beans 4272]

On 11/24/2018 at 3:38 AM, ruebiracer said:

Regarding your rear traction, I´m quite sure you choose the wrong rera tire, as I know the 60D wheels quite well since 1997. Also, your car is very light compared to even the lightest m-Chassis I guess. So pull on the 60D S-grip compound on the rear. This gives you the same look as with the std. radials, but far more grip even on could weather and rain. S-Grips are our superior rain tire in our M-Chassis championship, by the way. Pit Shimizu are also great tires, but the 60D can be twitchy, too. the 55d are probably the best for grip with the low side profile.  So if you ran on the open streets with some dirt on, I think the s-grips are your choice, also because of the thread.

Thanks for your insights on tires; I only have one M-chassis and don't race it, so I'm not as familiar with M tire options as with touring cars.  S-grips are now high on the list if the Pit Shimizus aren't satisfying.

22 hours ago, Yalson said:

The Stratos is one of those cars that looks amazing no matter what colour you paint it. If it has to be one of the above, I'd pick Red/Black/Gold, but have you considered painting it white and adding a full Alitalia scheme?

Yes!  In fact, the decal sheet HPI supplies is the Alitalia scheme with a few extra decals for doing a road / Stradale version.  Their "box art" is exactly as you describe.  It just felt "right" to do a road version.  I dream of owning and driving one on the open road!

14 hours ago, ruebiracer said:

Superb masking work already now!

Can´t wait to see the end result!

Thanks!

13 hours ago, VagabondStarJXF said:

Nice. Makes me wish I'd done up my rear window louvers in the same colour as my front and rear spoilers. I used a combination of smoke backed with gun metal because I thought that gloss black was a bit too 'strong' against the orange & silver scheme I went for. (Here's a link to my M04S Stratos)

You did a great job on your own Stratos; I see a lot of work in your custom chassis parts and body mounts.

So I finished painting today.  HPI's rear window mask fit and sealed perfectly so the clear rear window wasn't contaminated with paint.  A heat gun helped both before and after painting each layer; gently preheating the spray cans and body shell provided good coverage and no runs.  Gently heating the paint layer accelerated curing so I could get on with the next layer relatively quickly.  It was important (to me) to get all the layers deposited as soon as possible so I could pull the window masks easily.

Paint:  Two layers of PS-60 Bright Mica Red, backed with two layers of PS-1 White, backed with one layer of PS-5 Black, with windows shot in PS-31 Smoke.  Yesterday's splitter/wing/duck tail/louvers sprayed with two layers of PS-5 Black.

Results:

I think I'm happy with PS-60 Bright Mica Red instead of PS-34 Bright Red. It's just a shade darker avoiding that overly bright look.  It needs another day or two to dry completely.

[VagabondStarJXF 350]

9 minutes ago, speedy_w_beans said:

You did a great job on your own Stratos; I see a lot of work in your custom chassis parts and body mounts.

Thanks. I've been following this thread and I think your build is rather impressive. I look forward to seeing it all together.

10 minutes ago, speedy_w_beans said:

Results:

I think I'm happy with PS-60 Bright Mica Red instead of PS-34 Bright Red. It's just a shade darker avoiding that overly bright look.  It needs another day or two to dry completely.

Very nice. I really like the Mica Red. If I hadn't got the Orange & Silver thing decided beforehand, and if I didn't have so many models already done up in Mica Red, I would've done up my Stratos in this colour too.

[GooneyBird 938]

I've raced F1 cars on carpet, and have helped to setup 1/12th pancars (again, on carpet). I think the main issue is weight. You will want a bit of understeer, otherwise the car will be nigh-on undrivable. All the pan cars I've had in my hands so far were REALLY light at the front-end. If I had to make a guess I'd say they're about 70/30 rear-biased. Same with the F1 cars.

Diff: Go as loose as you can without it slipping. The thumb-trick is just to get you in the ballpark for diff-setup. After that, go looser until you start to slip the diff on a full-throttle take-off, then go slightly tighter. That's where you want to be.

[speedy_w_beans 4272]

8 hours ago, GooneyBird said:

I've raced F1 cars on carpet, and have helped to setup 1/12th pancars (again, on carpet). I think the main issue is weight. You will want a bit of understeer, otherwise the car will be nigh-on undrivable. All the pan cars I've had in my hands so far were REALLY light at the front-end. If I had to make a guess I'd say they're about 70/30 rear-biased. Same with the F1 cars.

Diff: Go as loose as you can without it slipping. The thumb-trick is just to get you in the ballpark for diff-setup. After that, go looser until you start to slip the diff on a full-throttle take-off, then go slightly tighter. That's where you want to be.

Yeah, as you may have read above, the weight distribution is 54% rear / 46% front right now.  The difference could easily be a 540 motor vs. a 380 motor in the rear pod (about 85 grams lighter).

The Pit Shimizu PS-0450 super soft tires showed up, and they are definitely soft.  The kit Mini Cooper Racing tires have a really stiff sidewall, almost to the point I have to wonder if the foam inserts do much.  The Pit Shimizus, on the other hand, definitely have a flexible sidewall and I can feel the support of the inserts through the slick contact patch itself.  I'm eager to try these.  It might be worthwhile to go back to gold kingpin springs up front.

The wheels are waiting for paint; it'll be a few more days before we get temperatures nearly good enough to spray them.  The minimum temperature for the paint I'm using is 60F; in theory we'll hit that on Friday.  Then again I might try to spray them on Thursday (51F) and get them back inside the house quickly.  The plan is to shoot them with black first, then paint the outside spokes and outer lips gold.  I can't seem to match any gold paint to the gold anodizing on the flanged lock nuts; those may have to be painted as well.  The tips of the blue axle stubs will need some gunmetal or black to match the 1:1 car.  Wouldn't it be cool to have some 4 mm Lancia logo decals on the tips of the axle stubs to mimic some center caps? 

The body shell has dimples for side view mirrors and a wiper, but the body set didn't come with any.  However, the Datsun 510 shell I did awhile ago came with an assortment of mirrors and wipers, so some bleach is helping me strip the chrome off the parts now.  These will be painted black.

I have some ABC Hobby fine line tape ready to define the panel gaps in the body, and some extra tape and hardware ready to help with body assembly.

The plan for body mounts is to go with Velcro.  I'll likely stick some aluminum tape inside the shell to protect the paint, then stick some Velcro to the aluminum tape.  For the body posts themselves I'm thinking about a Vernier-inspired sleeve design that will allow fine adjustments.  The hole spacing on the body posts is 3.5 mm, so if I make some sleeves with 2.8 mm spacing then I can adjust the height of the Velcro mount by 0.7 mm increments instead of 3.5 mm increments just by changing which hole has the snap pin installed.  This is similar to how you read between major divisions on a mechanical caliper, just in reverse to set distance instead of reading distance.

Concept:

Example of how the fine adjustment capability works.  The red dot represents where the body clip is installed.  It's a repeating pattern.

This should allow me to dial in the tire / wheel arch gaps very well regardless of the Velcro thickness.

I couldn't bring myself to put holes in the body for posts and went searching for other methods.  Velco, magnets, and some latching mechanisms all have their pros and cons; Velcro felt like the easiest from design, installation, and maintenance standpoints.

So, a little preview of things to come...