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  #201  
Old 26-02-2013
Typpo Typpo is offline
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Originally Posted by Origineelreclamebord View Post
I had a look at the Xray XB4 CVDs, however, they are actually shorter than the Tamiyas (strange being that they actually say '68mm'), and the head that goes in the outdrive has too big a diameter to fit. So, TRF201 Driveshafts it is!
After reading your more recent posts, you may find the following measurements helpful. Using the labels shown at the link below:

http://www.rc10talk.com/download/fil...7892&mode=view

Some corresponding approximate measurements in millimeters are listed here. Where ball diameter is the "head that goes in the outdrive"

Kyosho LA231-01 (A=9.75 B=68 J=2.0 with ball diameter 5.89 and axle cross pin used 2.0mm)
Schumacher U1915 (A=11.8 B=68 J=2.5)
Schumacher U2683 (A=11.8 B=70 J=2.5 with ball diameter 6.96 and axle cross pin used 1.5mm)

Unmeasured
XRAY 365320 with106051(according to manufacturer specification listed A=12 B=68 J=3.0)

Also I think the wheels used for the Kyosho and Schumacher axles listed, have 4mm hole diameters while the Xray and the Team Durango rear wheels may have 5mm diameter holes. Perhaps someone can verify this.
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  #202  
Old 26-02-2013
smokes smokes is offline
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Would a Double cardan joint be suitable for this application so you get a linear rotational speed what ever the angle?
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  #203  
Old 27-02-2013
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Wow, what a response guys!

@Typpo: That amount of info on the Kyosho CVDs is very interesting, thanks for sharing! I will do some comparison work in Photoshop between different pictures and what shows potential will be sourced.

I did find a slightly better option in the meantime than the Tamiya CVDs, being Tamiya's Universal Shaft wheel axles (not WO Universal/CVD) with the 65mm Durango DEX210 bones. It fits as if Durango copied the geometry of Tamiya's U-joints Ok, Tamiya's '64mm' shafts actually seem to be 64.5mm, so I only gain 1mm of width, but it is still 1mm wider, plus, the outdrive pins now have the perfect diameter.

Nonetheless, my search continues. There is room for improvement, hence no reason to stop searching!

PS: I'll also share the pictures of the Xray XB4 vs. Tamiya 201 CVDs to show you why the Xray axles are interesting and the bones are not suitable for my project.


@optiman: Nice B44 truck! My guess is that that car too will have some acceleration issues with only front wheel drive, but it's an easy and fun test Every time a 4WD buggy's drive on the rear breaks down I'm closely monitoring how it gets around the track, and to be honest for something that just happens on the spot they do pretty well


@smokes: A double cardan shaft may work very well - in fact, there are so many 'constant velocity' solutions out there that are interesting to have a look at... I'd love to make a Rzeppa joint for an RC car (the one in the center):



This does require too much customizing or even machining from scratch. Even the D-joint from Durango is a bit complicated to work with for now, but these things are worth thinking about (especially the double cardan joint because the availability of the D-joint or putting two CVD systems together)
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  #204  
Old 28-02-2013
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TD have recently released longer ball diff outdrives if that would help you #TD310417
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A list of option parts and other information for Durango vehicles. www.durangofansite.com
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  #205  
Old 28-02-2013
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Quote:
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TD have recently released longer ball diff outdrives if that would help you #TD310417
Do you happen to know how much longer they are? Because it sounds like just the thing I need - thanks for letting me know
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  #206  
Old 01-03-2013
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Sorry, wouldn't have a clue how much longer they are
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  #207  
Old 01-03-2013
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Quote:
Originally Posted by Origineelreclamebord View Post
Wow, what a response guys!

@Typpo: That amount of info on the Kyosho CVDs is very interesting, thanks for sharing! I will do some comparison work in Photoshop between different pictures and what shows potential will be sourced.

I did find a slightly better option in the meantime than the Tamiya CVDs, being Tamiya's Universal Shaft wheel axles (not WO Universal/CVD) with the 65mm Durango DEX210 bones. It fits as if Durango copied the geometry of Tamiya's U-joints Ok, Tamiya's '64mm' shafts actually seem to be 64.5mm, so I only gain 1mm of width, but it is still 1mm wider, plus, the outdrive pins now have the perfect diameter.

Nonetheless, my search continues. There is room for improvement, hence no reason to stop searching!

PS: I'll also share the pictures of the Xray XB4 vs. Tamiya 201 CVDs to show you why the Xray axles are interesting and the bones are not suitable for my project.


@optiman: Nice B44 truck! My guess is that that car too will have some acceleration issues with only front wheel drive, but it's an easy and fun test Every time a 4WD buggy's drive on the rear breaks down I'm closely monitoring how it gets around the track, and to be honest for something that just happens on the spot they do pretty well


@smokes: A double cardan shaft may work very well - in fact, there are so many 'constant velocity' solutions out there that are interesting to have a look at... I'd love to make a Rzeppa joint for an RC car (the one in the center):



This does require too much customizing or even machining from scratch. Even the D-joint from Durango is a bit complicated to work with for now, but these things are worth thinking about (especially the double cardan joint because the availability of the D-joint or putting two CVD systems together)
Litemodz do a version not sure how good they are though
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  #208  
Old 09-03-2013
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Thanks for the replies guys

@ekt: I emailed TD but they didn't respond... Since I will be picking up this project again after a few deadlines from school I thought I'd just order them. After all I can always shorten them if they're way too long

@smokes: The Litemodz shafts look awesome! I might email them to ask if any of those sets might be compatible for a TRF417... So I could actually try them out!

I also noticed that RDRP has released 'RR' suspension hangers (the ones I use for the front suspension) with different kickup settings. Sweet! That means the kickup it now adjustable from -3 to 3 degrees - if needed (with a 'kit' setting of 0).
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  #209  
Old 09-03-2013
mrspeedy mrspeedy is offline
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I'm pretty sure the std RR hangers could be shimmed up with washers anyway to give you some kickup ... thats how we adjust the FR hanger for antisquat ...
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  #210  
Old 13-03-2013
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I'm not sure it is possible on this car - without raising the gearbox. Not to worry though, the first proto seemed better off with less anti-squat/kickup, so this neutral setting should work nicely.

Anyway, I've got an update on the car again



So what's new?

- I (finally!) finished the rear shock tower and wing mount setup. I'm not 100% happy with the shock tower mount block, but it's the best I have done after some 4-5 retries at this and more than a month of thinking about it. I do really like the wing mount: The wing elegantly floats on two small mounts that attach to the single vertical plate that runs to the center of the chassis. It doesn't just hold the wing, it reinforces the shock tower too.
- The chassis has gotten another 15mm longer. This is to allow ever more space for the electronics, and at the same time shorten the rear arms. Less unsprung weight of course, but also, if the arms break - or an updated version is needed - they cost a bit less to replace.
- New front suspension arms. These are made to twist less because there is more distance on the narrowest point of the suspension arm. Also, the shock is moved a little to the back to allow a brace to pass in front of it. I also beefed up the arms around the suspension shafts - they are now 9mm around there instead of 8mm. I plan to do the same on the rear arms, but they're not finished yet. The front arms also have more room at the front hub, so the plastic DEX410R hubs (that have the grub screw in a different place) also fit on the car.
- Updated bottom chassis plate. Based on what I rear on breakage on the DEX210 of carbon and moulded plastic chassis around the holes for the suspension blocks, the chassis plate is 1mm wider on each side at the gearbox part - it doesn't sit in the way of the suspension, so why not reinforce it? Lastly, the part where the chassis gets wider at the front is angles further backwards (less 'square') - this is to allow more clearance between the tires and chassis on full steering lock.
- New front bumper. This one is angled more up to reduce the chances of it snagging on something or digging in - with some playing around on the geometry I also managed to keep the same amount of flex (=protection) on the front end.
- Shorter wheelbase. The wheelbase was ridiculously long (285mm), and I decided to shorten it a bit and give it +0.5 degree toe-in. I'm expecting it will need the added toe-in for stability with the narrower tires, but of course I'll only find out once I have the car up and running.

Edit:
A brief look at donor bodyshells:


The Schumacher K1 bodyshell seems to have a very suitable chassis profile. There is just one problem - for all existing bodyshells - on my car. The sidepods need to be much higher than usual. I might be able to achieve this with bodyshells that are not pre-cut (unlike the K1's body). So I need to find out if there's an aftermarket alternative yet for this car, or...

...I rotate the servo 180 degrees and put the steering linkage in the center of the car. This does mean no big electronics fit on the top deck anymore - and I'll make a small mount to neatly guide the motor wires. It does mean that I can run many more bodies on there (butchered or nearly standard), a good thing for the earlier stage of the project. A bit like this:


I do realize that the cab will be in an awkward spot on the car It's definetely not definitive what body I'll use, but I'm throwing it out here anyway what my findings are so far
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  #211  
Old 14-03-2013
mrspeedy mrspeedy is offline
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Sorry I really don't mean to pick holes cos I think you're doing a fanatsitc job ...

The rear suspension .. its slopes the wrong way ... surely it should angle upwards towards the front of the car, this should make it handle bumps better and squat less on power ... I'd also lay the rear shocks down as much as possible to give minimal weight transfer under power ..

Just my thoughts
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  #212  
Old 14-03-2013
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Hehe don't worry about it, all advice to possibly make the car go faster is welcome

To clarify what you're pointing out, do you mean looking on it from the side view, the arms should be horizontal, not sloped like they are now? Or do you mean when looking from the top view, the angle of the hinges should be changed? Or... Is my brain failing me and am I way off from what you mean? (It wouldn't be the first time it'd happen to me)

I'd love to make the shocks lay down more. In fact, I'd love to make gullwing arms. I'm not doing that because a symmetrical design is handy though in the prototyping stage - you need two types of arms in the spares box, not four. Laying down the shocks further results in a bit of trouble with the spring retainer at the bottom, they will interfere.

There are multiple solutions to this: using different rear shocks (no DEX210 front ones, but TRF201 front ones - small bore, and more importantly, 10mm shorter). I'd like to keep the same shocks all around though. Another solution is to use an insert piece that holds the shock that mounts the damper what would normally be below the rear arm. The part can be reversed to mount the arm on both sides, whilst also allowing a low mounting. I'll have to think about these options for a bit, they all have their pros and cons
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  #213  
Old 14-03-2013
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Nice job, Paul
Just don't be tempted into using the K1 body

Why not go all the way and get your own shell vac-formed-if you make your own mould, it's not that expensive.

Steven
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  #214  
Old 14-03-2013
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Quote:
Originally Posted by RC-trix View Post
Nice job, Paul
Just don't be tempted into using the K1 body

Why not go all the way and get your own shell vac-formed-if you make your own mould, it's not that expensive.

Steven
Thanks! and another thanks for confirming that about the K1 shell I'm not usually a fan of cab forward bodies (though somehow I don't find the K1's body that bad - on the K1), but once I saw in Photoshop where that cab would be I was having my doubts.

As for vaccuum forming, it's not so much costs (there's even a vacuum forming machine at school, the only question being if that machine has the right surface area for a buggy body). It's the time it takes to make a proper mould. I talked with Bugle about some experiments with Polyurethane foam for a bodyshell a while back. I haven't found the time yet to actually try it out, but the idea is to put a hard, heat resistant coating on the PU foam and see if it is durable enough for vacuum forming. If it is, it means I have solved the 'time' issue, a pretty nice PU foam model can be made in as little as 8 hours
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  #215  
Old 14-03-2013
mrspeedy mrspeedy is offline
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Sorry I'm not being very clear ..

Typical FF buggies below, pretty sure you will have seen these before, but they all have the rear wishbones setup with a good degree if anti-squat, which must help with reducing weight transfer under power and also allow the rear end to run better over bumps ..

Most of these also have the rear shocks laid down using a small standoff on the arm to raise the lower shock mount, I'm no engineer but most of what they did looks like it made sense, particularly the HPI version with its raised rear wishbone mount ... also looks the dogs doo da's to me

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  #216  
Old 14-03-2013
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Paul, a while back I had the chance to visit a professional vac-forming facility (in the Netherlands), and for low-volume work, they use plywood moulds with a few aeration holes.

They gave me a quote back then of about 50-80€ for a one fifth body.
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  #217  
Old 14-03-2013
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Thanks, I didn't look at it like that yet! Nice!

The height of the rear suspension hinges is already a bit adjustable on my car - the outer blocks can move freely up and down when spacers are used. The inside can move up to 2mm up. My plan was to try out different angles on the arms by spacing the outer ones further up than the inner one (or the other way around).

I think with a few small mods I can increase the clearance for the inside suspension block to move up by about 12mm - that should allow a lot of adjustment to find out how much of an effect it has on performance Though with 12mm of spacing the blocks might need some braces over the top (connecting to the chassis plate elsewhere) to keep the chassis plate in good condition.

By the way, what I did notice on the first proto is that the stance mattered a lot to the car. Raising the back end really made the car much more responsive and agressive. I'm not sure whether that's down to the anti-squat effect you described or the stance, but the stance as you see it in the SolidWorks model is not likely how it will be in practice (perhaps on high bite carpet, but otherwise certainly not)
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  #218  
Old 15-03-2013
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Quote:
Originally Posted by RC-trix View Post
Paul, a while back I had the chance to visit a professional vac-forming facility (in the Netherlands), and for low-volume work, they use plywood moulds with a few aeration holes.

They gave me a quote back then of about 50-80€ for a one fifth body.
I'm assuming that is when you supply the mould? If that inc. making the mould then I'm really interested, as a nice wooden mould still takes quite a bit of effort to make and machining services don't come cheap usually

Edit: I've spoken to the someone in the workshop at the university, and he expects that as long as it's coated, the PU foam should hold nicely. I also found a company who states on their website they often use PU foam (CNC machined) for their vacuum forming moulds. So now I'm on the lookout to find a nice coating for it that doesn't melt or become sticky and soft when the polycarbonate is pulled over the mould.
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  #219  
Old 15-03-2013
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Thats if I supplied the mould - but there may be less labour-intensive ways to make a mould, one of the employees was into RC and he had made ABS copies of a Tamiya body taking a cast.

Their site http://www.heku.nl/het-proces/vacuumvormen
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  #220  
Old 15-03-2013
mrspeedy mrspeedy is offline
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If you can get the mould lazer cut then MDF works just fine, its how we make most of our prototype work now ... its fine for one off's but the quality is not up to scratch for large quantities or for retail ...
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