Repairing a FS12-LT Engine (MRE TA01 Nitro Conversion Build Thread)

[futureworks 864]

Here's where it has got to this morning. I adjusted the positioning on the throttle arm on the carb so that it's as far back (towards the back of the car) as it can go before snagging on the engine/manifold when the throttle is fully open. Hence this gives me, as pictured the best position I can achieve with the throttle fully off. The only way to create any distance between throttle arm and throttle servo horn, it seems, is to orientate the latter in an offset manner - not visually appealing and an inelegant solution in my eyes, but that's where my thinking has got me to so far. (I wonder though if that leaves the braking action overly compromised). It leaves about 14 or 15mm between the connector holes on the throttle arm and servo horn (see yellow line on pic), so not much space, and the solution (as no space for putting in ball connectors and tie rods) will I think have to be a DIY metal rod between the two, a bit like those that are used on old MSCs. Happy to take soundings on all of the above if others have other ideas, suggestions etc.

[KEV THE REV 2319]

How about this . If you extend the length of the servo horn throttle arm to more in line or just past the throttle arm you could possibly make up a small ball link rod  . As the servo horn moves it will move in an arc , so the link will need to accommodate this , so it should sweep from stand still at just past the line of the throttle arm to just before the line of the throttle arm at full throttle

[KEV THE REV 2319]

How are you getting on with this ?

[futureworks 864]

2 hours ago, KEV THE REV said:

How are you getting on with this ?

I’ve bought a set of brake/throttle linkages for a kyosho inferno Neo 2/3, as I realised that I probably needed some other parts to help make all of the linkages work, and the parts looked like they might help. I’ve got the kyosho parts now, and might even have some time this w/end to have another go at this. Update coming in due course 👍. 

Another one of these nitro chassis builds also happened to pop up on the main club site the other day (so now 3 in total inc mine and acprc’s), so that’s  another TCer scratching their head over how to make this conversion work! https://www.tamiyaclub.com/showroom_model.asp?cid=137022&id=9189

[KEV THE REV 2319]

Ok , hope it works out , thanks for the reply 

[futureworks 864]

So, some progress me thinks. Those Kyosho Inferno linkages have been very helpful, along with a few other bits and bobs in the spares box. Essentially, whilst the brake arm side of things was straightforward, the throttle was the real headache. I tried a few ideas out until I thought about adding a further element of servo horn to the existing part, using a standard Tamiya kit part (the sort of servo arm you'd get for a mechanical speed controller on the TA01/2). This extra horn is mounted - with a spacer to raise it slightly so it doesn't snag one one of the alu parts making up the drive-chain assembly - onto the existing TGX Throttle servo arm, offset by around 45 degrees as you can see. On top of that is the throttle rod attachment piece from the Kyosho parts, which can swivel, which was a key reason for buying these bits. The throttle ball connector had to be screwed in on the inside side of the engine throttle arm as you can see.

Overall, I think it's not a bad outcome, not perfect and needs some minor adjustments still, but in essence, looks satisfactory from a 'reasonably neat engineering' perspective. I still wonder if there's a simpler approach - after all, presumably whoever actually designed the MRE conversion set for a TA01 back in the day had a clear idea about how the throttle linkage would work, despite the throttle/brake servo position being so close to any engine you'd care to fit.

Next step, will be to change the wheels to the 53140 Aluminum ones I put on a previous post, and also the Cross front and rear suspension sets, which includes carbon shock stays and stabilizers.

 

 

[futureworks 864]

[KEV THE REV 2319]

Now that's what I'm talking about.  That swivel part is the key . I bought a few of them from Blacksmiths products for my nitro projects . Looks great 

[futureworks 864]

3 hours ago, KEV THE REV said:

Now that's what I'm talking about.  That swivel part is the key . I bought a few of them from Blacksmiths products for my nitro projects . Looks great 

Thanks @KEV THE REV, your input certainly helped. I’m pretty chuffed with the end result 👍

[futureworks 864]

Having thought that I'd finally sorted out the throttle/brake linkages, a test I did shortly after the last post I made here told me I wasn't quite there. Felt a bit dispiriting to be honest, so left it for a week or so until having another crack at this today. This project has been so fiddly, as there's so little space to work with. I'd love to know what the designer actually had in mind for creating these linkages! 

The brake arm linkage works fine, that's never been the issue and the geometry is as it should be to enable the movement required. The problem was the throttle linkage, as the rod was not sufficiently horizontal - important given the very limited space between throttle lever on the engine, and the servo horn - so that meant it didn't have the smoothness of movement needed, and it was snagging and just looking awkward when moving. After a few experiments (including trying a different carb with a piston type throttle, rather than lever - from a FR-15S, and a different linkage arrangement - didn't work) I realised the best thing to do would be to keep the engine/carb as was, and raise the engine slightly. So I've inserted two spring washers for every bolt, added between the engine mounts and the engine itself. That raises the engine by about 1mm. I also made some minor changes to the make up of the small parts on each link rod, as what I’d done before wasn’t quite right. 

Finally now, this works smoothy for both throttle and brake - you can see both rods are horizontal, so everything is now as it should be (or at least, with the design I have developed).

[KEV THE REV 2319]

1 hour ago, futureworks said:

I'd love to know what the designer actually had in mind for creating these linkages! 

Now you know , they get paid for you doing all the R&D . glad it's worked out though . A lot of this kind of work is fiddly to say the least .