rich_f
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Posts posted by rich_f
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5 hours ago, OoALEJOoO said:
Correct, speed-realted losses indeed will affect the entire curve. Many of them are exponential with speed and therefore incurr heavier movement penalties the faster you go. The good thing is that qualitatively the trends on the graph would still be maintained (i.e. every ratio will be affected by speed, and not inherently by ratio). What could change, although I suspect not dramatically, might be the position of cross-over points
I think the effect on the crossover might be more significant. And I think that taller ratios will be more affected by the unmodelled losses than the shorter ones. I'll try to explain why I think this.
Your current model says that as long as there is some torque (given by the torque curve on the backs of boxes) then the car will keep accelerating until there is none.
Shorter gear ratios decrease wheel torque less than taller ratios, therefore taller ratios have less torque at all speeds than shorter ones.
Since actual acceleration is proportional to the excess force (after losses), taller ratios, which have less wheel torque (force) than shorter ratios at a given motor rpm, will hit their limit at lower rpm than shorter ratios.
The outcome is that there will be a point where going to a taller ratio results in a lower top speed in addition to lower acceleration than a shorter one (just as @Wooders28 recalls) - something your current graphs don't express.
So I think there will be a qualitative change as well as a quantitative one with the speed-related losses considered.
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8 hours ago, Mad Ax said:
at some point we'll have to decide what constitutes "low" and "high" gearing, which is a concept I've got confused with before. I've always used "low" to refer to low speed, high-acceleration gearing (probably from the automotive world where we say "use low gear for hills" or the agricultural world where we say "use low range for towing equipment") but I've heard others use "low" to refer to the ratio, i.e. 5.72 is lower than 8.35 but has a higher top speed
There are two ratios that people often conflate: gear ratio and speed ratio.
Generally people say gear ratio but they actually mean speed ratio. So a 7:1 ratio like a typical rc car means the pinion is spinning 7 times for every one rotation at the wheels.
As a gear ratio, this would be 1:7.
Confusingly, it is also possible (though not in a typical rc car) to have a 7:1 gear ratio, i.e., 7 times more teeth on the driving gear than on the driven one. So which is the 'higher' ratio - 1:7 or 7:1?
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2 hours ago, OoALEJOoO said:
Adding a friction & air resistance module would reduce final max-speed. Right now the model neglects them, resulting in max-speed at the point where the motor torque is zero (since losses are deemed zero). In reality, max-speed would be the point at where available motor tractive force equals all speed-related losses, and acceleration where available motor tractive force exceeds all speed-related losses.
That's not all it would do. It would also reduce speed all along the curve, because acceleration, as you say, depends on the amount by which the tractive force exceeds the speed-related losses. With unmodelled losses all along the curve, the taller gear ratios, which provide less torque at the wheel than shorter ones, so will have less excess tractive force than shorter ratios, therefore are shown in a much more optimistic light than would be the case in reality.
I'm other words, the unmodelled speed-related losses will disproportionately affect the taller gear ratios, so your graphs would look very different with them included in the model, and not just a shift downward for all ratios equally.
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On 9/23/2021 at 4:40 PM, OoALEJOoO said:
My concern from that method is that the diff resistance seems to be coming from increased contact pressure between the gears, caused by the shims. Wouldn't this indeed create more wear? I think this was Nobbi1977's point above.
I think you have to remember that the gears inside the diff don't move anywhere near as fast as the rest of the gears in the drivetrain. They only move during cornering, and even then only very slowly, at a rate proportional to the difference in path length of the inside and outside tyres around the corner, which is probably why no appreciable additional wear is being reported. I have also used this method with no extra wear.
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Could you...
- put the threadlock on the end of the screw then wipe it off with a cloth so that it's only occupying the root of the thread, therefore less likely to contact the plastic?
- put the threadlock in the hole and not on the screw?
- put the screw in then put threadlock on the end from the back of the hole (if you can reach it)
- use something other than threadlock that won't damage the plastic, like cyanoacrylate?
- use a longer screw and tighten a nut to the part extending beyond the hole?
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2 hours ago, foz75 said:
Is there any difference between the tamiya thread tap and a generic steel thread tap set? Just wondering if there's anything that makes the cost difference worth it? more accurate? better quality? ease of use?
Assuming you are talking about a normal thread cutting tap set, then yes, there is a difference.
The tamiya tool is a thread forming tap and not a thread cutting tap. The latter type cuts material away and the former doesn't - it pushes material out of the way to form the thread.
Which is more appropriate for the different types of plastic found in an rc car? I don't know, but tamiya don't appear to sell a cutting tap.
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36 minutes ago, Raman36 said:
On the Instagram presentation for TD-4 by TamiyaUSA, Fred says, it comes with Mod 0.6 which is also know as metric 48 pitch.
This may be the case but it doesn't make him or anyone else who uses this misnomer correct.
As others have said, 'metric 48d pitch' isn't a thing - it's either metric (module or mod) OR its the inch-based 'English system' (numbers ending in p or d.p.).
Someone somewhere thought one day that 0.6 module looks a bit like 48d.p. and was too lazy to refer to two different systems so they started calling it metric 48 pitch, but it's not, and this lazyness has probably cost more than a few people's 48d.p. spur gears when they inadvertently used incompatible pinions in their cars...
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I noticed this the other day, too. However, the section of the video in which those cars appear has the caption 'tamiya history' at the bottom in Japanese (I don't speak Japanese, but Google translate has a handy tool that allows you to draw the characters), so maybe this is just a section of their show where they talk about old cars.
I presume then that the wording in the description - 'Racing Master MK.6 and Road Wizard will be released!! ' - is just a dodgy translation into English.
If you turn on the chat for the video, you can see there were lots of comments when they appeared on screen. I'm not even going to try translating them, but I bet they were asking for them to be re-released.
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18 hours ago, Saito2 said:
Out of sheer curiosity, what's odd with how he pronounces, Avante, chassis and Tamiya?
And just to conclude this side conversation about pronunciation, the word 'chassis' is of French origin, and in the UK, and possibly elsewhere, it is pronounced the French way, with the 'ch' as a 'sh' sound, so - 'shassy' rather than 'chassy'.
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2 hours ago, matisse said:
Can’t unhear how he says Avante….
And chassis, and Tamiya 😂
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15 minutes ago, Juggular said:
I never use gray primer. It makes the color you paint very dingy; like turning yellow into light brown.
The different primer colours are for use with different paint colours. You don't use grey primer with yellow for the reason you point out.
Generally, grey is a good primer colour for dark colours and white for light colours, although you can get specific primer colours like red or yellow.
One less obvious reason for primer is that paint is sometimes translucent, whereas primer isn't. Any hint of translucency will make the final paint job look less solid and more plasticky.
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If you've got access to an airbrush, then nail varnish is a good source of these more unusual colours. I painted a dodge charger model in the closest nail varnish I could find to 'plum crazy'.
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5 minutes ago, djmcnz said:
I'm sure you can buy different wheels if you need them.
Likewise you can buy hop ups for the 40th anniversary version if you need them.
6 minutes ago, djmcnz said:packaging
The box for the 40th was in my opinion one of Tamiyas better ones - the different views of the car from different sides of the box, plus the carry handle. No blister packs but they don't do anything for me anyway - but it seems the 45th will have them so that's a plus if they are your thing.
The 30th box was a bit plain in my opinion, similar to the 45th. Not a fan. And the fact it is just a photo makes it even less desirable for me.
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1 hour ago, c64orinoco said:
Will the PS paints stick as well to polystyrene as they do to polycarbonate? My mind says they would, polycarbonate seems to be more difficult to stick to.
I always use primer on polystyrene shells meaning any subsequent paint will stick, and I usually just use car spray paint for the main colour. Is there any reason you are restricting yourself to using tamiya paints?
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1 hour ago, djmcnz said:
But the writing is on the wall with this one, 30th was awesome on all counts, perfect even...
Perfect? What! The wheels it comes with are so out of scale that it looks like a toy! Or worse - something from pimp my ride.
Given that they designed bespoke wheels for it, and assuming they wanted to use 'standard' sized tyres, they could have used the same 2-piece wheels as the taisan gt2 but with bespoke new centres to match the older style, which would have looked better as: 1. they'd have smaller centres more like the real car and 2. the rears would have been wider than the fronts like the real car.
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1 minute ago, svenb said:
looks excellent but is it me or is your battery holder further back on the chassis compare to the Tamiyabase pic?
It's not you - the chassis has extra holes for mounting the holder in different positions.
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Let this be a lesson - when you buy a screwdriver with a replaceable tip, buy a replacement tip at the same time! That's what I did with my EDS JIS screwdriver (which fits fine in tamiya screws - though mine is a 5.8mm and not 4mm)
I'm sure you'll be able to find a replacement tip somewhere, even if it's a different brand.
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9 minutes ago, rwordenjr said:
eBay is losing out but the seller should be banned from creating new account so it’s a 1 time scam I think
Unless they sell multiple scam items in the time it takes to get them banned... Plus they can just use a vpn to create another account and repeat.
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23 hours ago, TamiyAddict362 said:
For those with fake sidewalls, yes I've seen some, but I personally don't like it. Perhaps I want the whole thick tyre to be real rubber.
For my Porsche 934 project (still yet to be started), the only scale looking wheels I found were ones with the fake sidewall. I decided to try HPI vintage tyres with them and most of the fake sidewall is covered by the extended sidewall lip of the HPI vintage tyres, so that could be an option.
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Yes - it looks like you are using a mix of TA01 and TA02 kingpins, which are different sizes and made of different metals.
The TA01 ones are longer and you can see they protrude more than the 02 version.
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16 hours ago, nowinaminute said:
That's the risk ebay take by offering you a money back guarantee.
And the reason ebay has fees...
17 hours ago, nowinaminute said:The account the money went to will be long gone by the time ebay try to recover it. Ebay will refund you but they will never get the money back from the seller
This is almost certainly what's going on. They quickly sell a few, send out the bogus packages and while they are being delivered, the account is closed down. Then they do it all again with another ebay account and another bank account.
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17 hours ago, SupraChrgd82 said:
Do any of y’all know what Tamiya means by “Radial Tires”?
I think that they mean tyres with a tread pattern on, as opposed to slicks.
Not quite sure why they have chosen to name them radials though as they certainly don't have any strengthening cords inside - cat whisker or otherwise.
Maybe it started as a marketing thing for real road car tyres - that they became known as radials (because when radial tyres were introduced they offered a superior ride to cross-ply tyres that came before). And since road car tyres have treads, maybe that's why tamiya uses the name 'radials' to distinguish them from slicks.
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13 minutes ago, Badcrumble said:
Am I right in thinking that some kits - like the M04 Giulia - come with mixed compounds?
If so, how do you tell them apart? I guess the model number on the sidewall?
My M04 mazda mx-5 came with standard kit tyres on the front but s-grips on the rear. S-grips and M-grips have S-Grip and M-Grip on their sidewalls, respectively. Standard kit tyres just have the number and Tamiya on the sidewalls
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1 hour ago, Juggular said:
I wish I knew about the compound. If I buy M-Grip would it be softer than this or harder? If you bash parking lots regardless of weather, this could be considered "all season?"
The standard kit tyres are harder than M-Grip. If you're a car park basher then yes these can be considered all season.
I always used to race with these on the front of my M03 on carpet with S-grips on the rear.
Outdoor on dusty tarmac I would use S-grips on the front and Type-A slicks on the rear.
I've no experience with the super radials.
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Ball Nuts and Ball Studs Part Numbers?
in General discussions
Posted
Or the short ball nuts are 9808012/19808012.
I have some here and indeed they don't stick to a magnet.