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Touring by h2e (1/10th, 190mm, 4wd)

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Touring by h2e (1/10th, 190mm, 4wd)

Old 12-05-2020, 05:21 AM
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Default Touring by h2e (1/10th, 190mm, 4wd)

Dear RCTech Forum,

I've been a keen reader for years, but this marks my first post in this forum. More of a tinkerer (yes, I am an engineer) than a fast racer, I am in the process of designing yet another touring car, and I would appreciate your opinions - positive or negative - on some of the specs I'd like to try to achieve with that design. Please be aware that I might take some of your ideas to reality, and some not (so please don't be offended). It's intended as a personal project for fun and understanding - with no precise future plans. Please always try to explain why you prefer some solution over the other. Thanks!

1/10th Touring car h2e concept
Chassis
- The main goal of the new design is to create a much shorter/narrower (at the bulkheads) chassis plate in contrast to AMX, MTC2, Mi7, even more extreme than the BD10 or ARC R12
- Why so? To maybe be able to lower the chassis by some 0.5-1mm
- The current concept compares to a TA07 (RCLabHK) as shown

Drivetrain
- Goal: Minimal drag, balanced acceleration/deceleration delivery
- Single belt (not to be discussed ), to allow for easy motor position changes
- More or less centered transversal motor with ESC behind
- 37t diff/spool to allow for removal of recess holes around them whilst still keeping a decent CoG height.
- As large as possible counter pulleys to reduce drag
- Belt lenghts optimized for balanced braking torque "reaction speed" on both axes --> 257mm wheelbase
- Even if it wouldn't be needed: Diff clamps are made as inserts to allow for different brand Diffs/Spools in the future (as decision is not yet made)

Suspension
- Goals: Full typical adjustability, low unsprung weight, tuneable caster stiffness (means I want to do FE-Analysis), crash-resistance as good C-hub designs
- 4 similar corners, just assembled differently
- Lower Arm: Inner hinge pin suspended (like Tamiya), outer hinge joint with ballcup/ballhead like AMX --> allows for more robust arm but keeps unsprung mass acceptable
- Suspension pin goes through the diff holders, to minimize # of holes on the chassis plate
- Suspension pin has eccentric insert, to allow for tuning of roll center
- Tamiya-style steering knuckle with ballheads top and bottom (no C-hub) --> I personally don't like the AMX parts, as the steering link sits high (and I have a lower link position in mind for the chassis side)
- Upper arm AMX style, maximum triangle shape, but much attention is paid to the bulkhead stiffness/strength, i.e. most of the flex should be in the arms, not bulkheads. As the A-Arm needs to "bend" around the damper, it is slightly curved, similar to MTC2.
- Damper: Tamiya SSBB damper body only, to have a lighter, more compact and lower CG design
- Spring: lateral leaf spring, own design, but inspired by AMX, to be more easy to adjust

Others features:
- Bumper spaced higher by 3mm, to reduce chassis dragging, load path for crash goes into (pinned) bulkhead (hopefully not causing too much crash-induced tweak)
- 2pcs servo mount, possibly allowing different stiffness designs (never mounted to top deck)

Open Questions:
- How important do you rate
a) narrow chassis,
b) short in the back chassis,
c) short in the front chassis

- Top deck design: 2pcs AMX-style, or TA07MSX-style, 2-rail vertical topdeck? Which one is the most versatile, i.e. allows for the largest stiffness range?
- Damper bridge: what is your preference:
a) carbon piece on the outer edges of bulkheads (like Mi7, Serpent Medius),
b) over the diff (like Tamiya, Xray) or
c) a damper bridge from Aluminium like MTC2, Corally? I look for a design with minimal CoG, sufficient stiffness for the damping forces (only), but possibly also a stiffening effect on the bulkhead?
- What do you consider as the benchmark in unsprung mass (wheelhub, A-Arms + camber links, springs+retainers, damper shafts, all outer ballheads/shafts, ARB supports etc)
- What do you consider as the benchmark in height of CG? According to RC^3, the AMX A800MMX has 28mm, can anyone confirm?

Sorry, no pics so far (new to the forum).

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Old 12-05-2020, 10:35 AM
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Very ambitious task, you give yourself
I am looking forward to your development.
What was your decision against the shorter Xray or Yokomo shocks?
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Old 12-05-2020, 12:13 PM
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Hi wtcc, it's funny you write me, I was just thinking to comment on your KR builds. These projects have probably inspired me to do a full build, in contrast to some TA07 mods up to now. BTW congrats to your creative and different designs!

The shock body question is not definitely answered, that's just what I had lying on the desk (i.e. I could measure all dimensions). If Yokomo or Xray are smaller in outer diameter, they might be considered. Diameter is what defines my design, as I squeezed the damper behind the driveshaft, and at 35deg steering lock (back of wheel closer to bulkhead), the wheel hub almost touches the damper.
Still tinkering with damper/leafspring position.

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Old 12-06-2020, 09:34 AM
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The only thing I dislike in single belt car is that by design, you are always getting traction in the rear first and then in the front… The opposite would have been preferable I think, but it is very hard to get…
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Old 12-06-2020, 12:14 PM
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Agreed, it may have been a small issue with high gear ratios and strong motors on the TA07. I have since flipped the idler pulley and spur gear position, and with about 130mm belt length to the rear pulley and 350mm to the front, the effect is not really noticeable anymore. I am faster with my TA07 (RCLabHK Carbon chassis) than with a 419X.
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Old 12-06-2020, 02:50 PM
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You may want to think about your decision to put the hinge pin mounts on the diff holders. This was common a few years back but it may make the car too stiff. Xray, Corally, and Associated among others did this when foam tire racing was big in the USA, but the majority of cars now mount the suspension to the chassis.
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Old 12-07-2020, 01:50 AM
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Originally Posted by h2e View Post
Hi wtcc, it's funny you write me, I was just thinking to comment on your KR builds. These projects have probably inspired me to do a full build, in contrast to some TA07 mods up to now. BTW congrats to your creative and different designs!

The shock body question is not definitely answered, that's just what I had lying on the desk (i.e. I could measure all dimensions). If Yokomo or Xray are smaller in outer diameter, they might be considered. Diameter is what defines my design, as I squeezed the damper behind the driveshaft, and at 35deg steering lock (back of wheel closer to bulkhead), the wheel hub almost touches the damper.
Still tinkering with damper/leafspring position.
Xray ULP: 15,0mm diameter at upper cap, body 12,3mm and lower cap 10,8mm
Yokomo BD10: 14,8mm, body 12,8mm, lower cap 10,5mm

If length isnít a problem, than maybe standard-non-big-bore shocks are better suited.
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Old 12-07-2020, 10:42 AM
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I guess this is an important point. Chassis designs vary from ball joints (L and R not connected) to connected ball joints via a brace, to pins (separate blocks FR?RF) to braced pins (single blocks). You hardly see bulkhead mounted designs anymore.
I would adopt this to be able to shorten the chassis by 34(!)mm, and have the A-Arm support overhanging from the chassis. All in all, if I had torsion stiffness ranges that are competitive, I could design the top deck accordingly. So far the plan is to build a little rig to test my TA07/Schumacher Mi5 (soft) and TRF419X (max stiff setting) - if no one is showing up with magic numbers.
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Old 12-07-2020, 10:45 AM
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Originally Posted by wtcc View Post
Xray ULP: 15,0mm diameter at upper cap, body 12,3mm and lower cap 10,8mm
Yokomo BD10: 14,8mm, body 12,8mm, lower cap 10,5mm

If length isnít a problem, than maybe standard-non-big-bore shocks are better suited.
Thank you wtcc for the quick reply! CoG is my main concern, so I might sacrifice shock position in longitudinal direction for lower CoG. Currently I am thinking of not mounting the shock with a ballhead/ballcup on the top, but with kind of a clamp brace around its main body. This way, the damper stay could be lower than the top deck. Any opinions about this?
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Old 12-08-2020, 11:38 AM
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I've read some stuff about damping, and on 1:1 touring cars, rebound damping seems to be about half the value of compression. That would imply, that the shock shaft cross section area should be half of the inner damper body area... We are nowhere near this with current big bore dampers...
What do you guys think?
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Old 12-08-2020, 12:11 PM
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Originally Posted by h2e View Post
Thank you wtcc for the quick reply! CoG is my main concern, so I might sacrifice shock position in longitudinal direction for lower CoG. Currently I am thinking of not mounting the shock with a ballhead/ballcup on the top, but with kind of a clamp brace around its main body. This way, the damper stay could be lower than the top deck. Any opinions about this?
Hello h2e. I don't have the technical depth to help you with most of your questions, but I have a suggestion. Try adding some images, drawings, inspirations, etc. so that more people can understand what do you want to achieve or what you're proposing.

For example, I can think of a clamp brace around the body of a shock in a way that works, albeit probably not better than the ballhead/ballcup solution that already exists., and I can also think of a solution that definitely doesn't work. Maybe you have a great solution, but only with words it can be too vague...

What I want to say is that most of this innovative solutions are a merit of great design. And that can't be put into words.

Anyway, it's just a friendly tip that may or may not be useful. I'm looking forward to seeing your project delevopment. Good luck!

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Old 12-09-2020, 09:24 AM
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Thanks mr.rev,

You are absolutely right, that pictures say much more than what I wrote. Well as a new starter in this forum, I am not yet allowed (no clue, how many posts are required to do so).
In the meantime, I prefer to evolve the design, even if questions and answers may be a bit wordy. Pictures will follow for sure. As the todo list is still quite long, I am not sure what is most beneficial/satisfactory for you guys and the project.
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Old 12-09-2020, 09:41 AM
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Chassis concept side view w/single belt routing. Shock position still evolving
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Old 12-09-2020, 09:46 AM
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This is how much smaller the chassis would be compared to a TA07 (RCLabHK). about 30mm...
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Old 12-09-2020, 10:17 AM
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Since the single belt drivetrain is not to be discussed and it looks like you already have that pretty much figured out, I suppose I'll focus towards the suspension. For the record, I think that the dual belt design has better tunability and practicality.

Would you care to share a top view image of your concept? I fear that to get the structural rigidity needed for the suspension to work properly you would need to add quite some unsprung weight. Also in a relatively high position. It looks like CG would be higher than in the new mtc2 (regarding the suspension only), for example.

Another point of concern is that (maybe?) this kind of design limits shock angle adjustment. Not shure if it's a big deal, though.
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