TR-15T Brushless Monster Racer Conversion

[Ann3x 222]

So instead of continuing to hijack KonteMax's build thread, I thought I'd post my own :).

Background: I love the Astute family of cars. I own a restored Astute, Super Astute, Dynastorm and a Hilux Monster Racer (fitted with a Dynastorm transmission) already. I love the technical evolution across the series with each model solving specific problems that the predecessor had (reaching a culmination in the Dynastorm imo). There is however one outlier in the series - the TR-15T.

Coming last of all in the series and being Tamiya's 1st ever Nitro car it falls in spirit somewhere between the Dynablaster and the KingCab. A Nitro powered, mid engined, low slung tarmac racer it's always struck me as something of a strange beast but with some really interesting properties:

• Fibre Reinforced parts (many physically identically to the DS but much stronger material)
• Mid Engined - The gearbox is reversed compared to the Dynastorm/blaster giving it a mid engine and also a totally different "Motor plate" with mounts on the opposite side.
• Nitro Engined - A 1st for Tamiya, it has a Nitro engine (which I despise! - far too noisy and messy for my tastes)
• Low slung - It's a stadium racer but with buggy sized tyres and clearance?!?! Why? It's even lower than the dynablaster!

When an opportunity came to get one NIB for a reasonable price, I couldn't resist but to satisfy me properly it would definitely need converting.

The Goal: "Sympathetically" (ie using as many original Tamiya parts as viable and in a way that Tamiya themselves might have done it) convert the new TR-15T to electric whilst remixing it to be more like a "proper" monster racer (eg HMR, KC). I'd like to end up with something that looks and handles like a KC/HMR (or better given the mid-motor) but still has the TR-15T's general theme.

The Plan: In order to achieve this goal a fair few parts would need creating or modifying:

• Dynastorm Battery Tray
  • I feel that this is a part that Tamiya might have used if they had produced an electric TR-15T
  • Takes "traditional" stick packs (shorty packs just feel too "new" too be right here)
  • Chassis needs to be re-drilling to fit the battery tray
  • The height of the DS battery tray is 25mm but the TR-15T support posts are 27mm
• Custom Motor Plate
  • A DS plate wont work due to the "mirror image" issue of the reversed transmission (mount holes are on wrong side, offsets are reversed). Max explains this well in his thread so I won't reiterate.
  • Needs a Spur cover solution - As a nitro car the spur is exposed. I could either leave it exposed (bad imo) or use a DS motor cover (further complicating the hole pattern of the motor plate)
• Custom Top Plate
  • The TR-15T top plate is wholly unnecessary on an electric (big cutouts for engine, tank and servos), it's way bigger than needed and is a 2 part piece but it does have a quite distinctive shape that I'd like to retain.
  • Also to take a traditional stick battery pack WITH the mid motor, longitudinal space on the chassis is limited, the original steering servo location won't work, I'll need a new approach using a top plate mount.
• Custom Body
  • The TR-15T body has pre-made cutouts for the nitro engine which are redundant for electric and will result in a weakened body and lots of dirt ingress.
  • After a fair bit of research, I *believe* that the body is based from the Stadium Blitzer mould with some modifications (lengthened wheelbase, hood vents and external rollbar), with some styrene work it should be possible to replicate the TR-15T and still avoid the "nitro gap". Needs some more thinking here.
• Conversion to "Monster Racer" shape.
  • Wheels are fine as is (standard size 2.2 same as Dynblaster) but Tyres are far too low profile to be a real monster racer
  • Shocks are too short for "true" Monster Racer suspension travel
  • Some geometry might need adjusting (eg anti-roll bars)

1st stage is to mock up what I want to do with some easy to handle materials to check for anything majorly flawed in my plan.

[Percymon 2185]

Interesting project - look forward to seeing your progress

[Ann3x 222]

So, onto phase 1. Mocking up:

Motor Plate:

I need a motor plate that fits the mirror image transmission but can also accept the dynastorm cover. Hmmm. Hardboard mock-up time!:

Dynastorm on left, TR-15T on right, note that the 3 threaded holes that attach the plate to the gearbox are mirror images.

When held back to back, the gearbox holes line up perfectly but the case holes are in very different places.

Rough mock up from hardboard:

Looks pretty good! This is all 3 plates stacked up together:

With a "Motor":

 

And now on the car:

It's a tight fit but it will work. The gearbox cover JUST clears the shock tower but does bind on the suspension pin plate which will need a slot taking out of it.

[Ann3x 222]

Now for a mocked up top plate. Cardboard should be perfect:

I will make my top plate one piece of 2mm Carbon Fibre vs the 2 piece FRP of the original. I don't see the point of FRP nowadays, its just as hard to work with as CF and much heavier. To consolidate the 2 part TR-15T top plate into one piece, I'll use a dynastorm plate as a template for the front and the TR-15 plate at the rear with the mesh point being the steering posts:

As I said initially, there won't be room for a steering servo if I use a centrally mounted stick pack so I need to create space for the servo within the top plate. This might (will) cause some issues fouling the battery installation but I think I can find a workaround for this.

Overlayed onto this are the holes for the Dynastorm battery plate, I will use the original grey TR-15T engine mount as a backplate for the battery.

Fit's well:

You can see that I've also started with the geometry mods to make it more like a Monster Racer. Short Re-Re Hi-Caps all round with some longer HPI 61mm shock shafts in the rears (with limiters) and the standard tamiya "long" hi-cap shafts in the front. I've got some Proline Dirt Works on the rear and you can see the size difference from the fronts. New fronts are on order.

I've also mocked up a steering rod from some 2mm wire. Seems to work fine but as I suspected it fouls the battery preventing easy removal. A bent link might work? In any case, I'll work this out later. Now onto the build proper:

1/ Drill chassis

2/ Cut Motor plate from Aluminium

3/ Cut CF Top Plate

[Percymon 2185]

A shorty li-po battery pack  might help..

 

1. perhaps able to place transversely across the chassis

2. mount longitudinally and be able to move forward/aft to balance the chassis

or

3. mount longitudinally towards the motor and create sufficient room for the steering servo at the front

 

[Ann3x 222]

Oh definitely, a shorty would solve all issues easily and I have 3/4 of them in fact. But who wants easy! :).

Shorties didn't exist when the dynastorm / TR-15T was around and one of my aims for this build is to stay true to the "spirit" of that time. So a stick pack it is!

I will find a workaround for the steering rod.

[Percymon 2185]

Very true !

 

What about a 6 cel hump pack then like the Sand Scorcher ?

[KEV THE REV 2433]

Nice project . TR15T body shell is more Dyna Blaster than S/B . The TR15T body is only pre-cut around the wheel arches so you could use an original un-cut , or a TBG one

[Ann3x 222]

1 hour ago, KEV THE REV said:

Nice project . TR15T body shell is more Dyna Blaster than S/B . The TR15T body is only pre-cut around the wheel arches so you could use an original un-cut , or a TBG one

The one I have is partially pre-cut around the engine hole too (curved areas only). Maybe some variation in kit prep during the run....

Do you have a pic of the SB vs DB? From my pov this is why I think SB is closer related:

The angles of photos ive used dont do it justice and the SB seems to have no hood bumps in some photos (and definitely does in others), but after a lot of squinting at photos of other trucks, my TR-15T shell and my hilux I think SB is closest....

[KEV THE REV 2433]

I've got a DB shell in TR15T livery which had a TR roll bar fitted to it and no cut out in bed . I'll get a pic of it next to a TR15T shell . Probably overall more authentic than the SB shell with cast in roll bar. Need some time to get this done

[Ann3x 222]

Ok so, 1st phase of the build itself is to drill the chassis for the Dynastorm battery mount.

Fist line up battery mount with chassis and mark out. I did this using the battery pack I intend to use (a std stick) hemmed in at the rear by the nitro engine mount which has pre-drilled holes. You can see I have trimmed a gap in the front of the battery tray for the wires to escape from under the top plate.

Mark the holes using the dynastorm battery case as a jig (I clamped it in right place, checked it was properly aligned then ran a fine drill down each of the 6 holes to mark hole location). Drilled with a 2mm drill then a 3.5mm then countersunk (it's quite a deep countersink, I ended up using an 8mm drill on slow speed).

From the top:

Looks good! You can see a little raw aluminium around the countersink, but that cant really be avoided without re-anodising (ain't happening!):

You can now see that the TR-15T has 27mm uprights vs the 25mm height dynastorm.

Weirdly the TR-15T steering pillars are 25mm - notice how the dynastorm battery tray is the same height as them at the front:

So the FRP top deck as standard must be angled!?

No! in fact this is because the "normal" TR-15T has a 2 part (and 2mm thick!) FRP top plate. This is where the offset comes from (this took me a while to work out....). By replacing the 2 part top deck with a stiffer 1 part unit I have caused myself an alignment problem!

I think I can either:

1. Put 2mm spacers on top of the dynastorm battery tray - but this still leaves the steering & front mount points 2mm too low (I could use the original FRP front plate as a spacer i guess but feels a bit messy).
2. Shave 2mm off the TR-15T engine mount and chassis posts

I wanted to make this a non-destructive conversion but I'm erring towards #2 now.... Seems neater.

[Ann3x 222]

Anyway, I still need to solve the top plate height issue but that shouldn't stop me fabbing some more stuff. Motor plate time.

I took my mock up and cut out a real plate from some 2mm aluminium plate I had hanging around.

• I Drilled 2.5mm holes to start for every hole, using my mock as a template (3mm tapped, press nuts and larger holes) then drilled the big holes out with hole saws.
• Initially I tapped the gearbox mount holes with a 3mm hand tap but it felt a bit delicate, with some experimentation I think there is space for some slim press nuts which will be much stronger.

Press nuts attached by redrilling to 3.5 (or 4) mm, then using a washer and bolt to seat them firmly.

Notice the different thickness of press nuts on each side of the plate. There is no space for the thicker nuts behind the Spur but plenty to seat the gearbox cover on, more threads = more strength!

So far, so good right?

Wrong. I have miss-aligned my mainshaft bearing hole (the most important one!) :'(:

This is a terminal issue because the TR-15T mirror mounted gearbox relies on a bearing seated in the motor plate to counter the extra layshaft length from the mirror image transmission. If I want to use the original 10mm OD flanged bearing - I have to start again! 

I figure the best option is to try and re-align the hole by extending to 12mm and using a bigger bearing (there is space between the plate and gearbox). This is a shot in the dark as realigning a pre-drilled hole is random luck (and rarely works). Still, a bit of filing, a 12mm holesaw and hey presto!:

With no small amount of luck you can see a 12mm OD/ 6mm ID flanged bearing fits perfectly!!! Wow - I got really lucky there. You can see the bearing size difference compared to original:

I'm not so happy with the motor mount holes (especially the slot) as they are a little messy but, lets see once I get a pinion to fit (I think a 19t will do given wheel diameter). They do physically fit, just a bit off-alignment and messy.

On goes the slipper which is *similar* to the dynastorm/blaster. Note the *similar* comment.... In fact there is one difference, the TR-15T clutch has 3 alloy spacers (circled in photo below) which seat under the clutch bolts. If you mount it with these installed under a dynastorm gear cover the clutch then fouls the cover (it took me AGES to work out what was causing the binding). I have no idea why the TR-15T has the 3 spacers as they seem to serve no purpose.... weird. Remove them and all is good.

Slipper now fully mounted:

In order to mount the gearbox cover, a small notch is required in the suspension hinge pin plate otherwise it fouls. I dont think this should affect rigidity a lot, other option is to mod the gearbox cover but these are rare items....:

Now it mounts nicely:

It JUST clears the rear shock tower:

One thing I realised after I fitted the motor plate. The dynastorm and TR-15T original motor plates are actually 2.5mm (vs my 2mm plate). I hope this wont matter too much.... I hope.....

Next up the carbon top plate.

[Collin 2047]

The split upper deck wasnt that bad design. With removing some screws you can lift it up and clean the car much easier. No removing of servos and all electric. Great invention for a Nitro.

[Ann3x 222]

28 minutes ago, Collin said:

The split upper deck wasnt that bad design. With removing some screws you can lift it up and clean the car much easier. No removing of servos and all electric. Great invention for a Nitro.

Interesting.... Shows what I know about nitro :). 

For me, as an electric guy, it's just more flex & weight but I can see the advantage with the dirt you get from a nitro (that's why I'm not a fan). 

[Collin 2047]

I would do a sandwich upper deck. Both, DS front and custom deck glued together with epoxy.

Btw. its just a question of percent of gasoline in your veins, if you like nitro or not.  

[kontemax 1780]

14 hours ago, Ann3x said:

So instead of continuing to hijack KonteMax's build thread, I thought I'd post my own :).

It was not a problem

Max

 

[Grastens 2802]

I admit I was skeptical at first, but I see now that this is an inspired retrofit!

@Ann3x, I don't suppose this means you have a complete nitro engine and fuel tank for sale? I happen to have a beat-up TR-15T that could really use those parts; such a deal would really kick-start the restoration...

[Ann3x 222]

2 minutes ago, Grastens said:

I admit I was skeptical at first, but I see now that this is an inspired retrofit!

@Ann3x, I don't suppose this means you have a complete nitro engine and fuel tank for sale? I happen to have a beat-up TR-15T in parts that could use the motivation...

Collin already asked me the same question in fact. Atm I'm planning on keeping the engine (so the mod is theoretically reversible at least). If that changes I'll be sure to give you both a heads up. 

[Grastens 2802]

Noted! The engine on mine is quite incomplete, all the tubing is missing, and the fuel tank is a lost cause, so anything would be appreciated.

In the meantime, I will stay tuned to see where this build goes

[Ann3x 222]

Sooo.... A carbon top plate.

1st I have made a better template that is more accurate and includes the front section as one piece:

Note the cut outs either side of the battery's rectangle. The DS battery holder has raised grooves on top to seat the DS top plate at each end. In the cutout I've just put in the front perpendicular cutouts but there are also rear ones which are slanted. To make it fit you could either shave the DS battery tray so the top is flush (then no extra holes needed) OR you need to put in recess holes as the per my template.

In the spirit of my non-destructive conversion I'm going to make the holes.

Time to prep for CF handling.... Mask, glasses and dust extraction are essential imo as this stuff is killer for your lungs. Also might want to consider some gloves as the splinters are quite nasty (I didn't, my hand regrets it!). Anyway, to cut it I 1st clamped the template to the CF sheet, then used it as a jig for the screw holes, m3 bolts through the 4 corner holes to "lock" position before moving onto cutouts.

I drilled holes in all the corners for the "big" cutouts (size of hole depends on radius of corner I wanted to achieve) so that I don't need to dremel right into the corner (easy to overshoot with a vertically oriented rotary tool). Then its a case of following the template edges with a cutoff wheel on a slow-medium speed (a few sizes of cutoff wheels helps a ton here - keep hold of your small ones). After that hand files and sanding drum on the dremel to smooth off the edges.

Eh Voila:

One carbon top plate.

The edges are pretty good but screw holes are a bit scruffy and there are a few work marks if you look closely. Nevermind, the screw holes will be covered by the screw heads themselves and with hand tools it's always easy to scuff a surface or 2, I think you'd need laser cutting or significantly better tooling (and more skill) to achieve a lot better. I've chosen to use button headed screws on my top plate but you could countersink if you want for a tidier finish. The one hole I have countersunk is the aerial hole which is CS on the reverse side of the plate - a proud screw there could be a catch point otherwise I think.

General fit looks fine:

Notice the new proline rib tyres are also on now - it's looking a lot more monster racery :).

I still need to seal the edges of the CF to avoid delam. this is best done via the perm marker + CA glue on a cotton bud approach imo. I like to buff the edges to a polish after drying purely for cosmetic reasons.

Well, it went fine (fine meaning I only stuck my fingers together once ). A little acetone solves that anyway. A nice shiny edge that shouldn't delam too easily. I've buffed up the straight bits but the notches Ive CA coated but left unbuffed (no access for a dremel).

Time for a more thorough test fitting:

Starting to look close to finished now. Let's bolt it down properly and mount the steering servo etc.

In general - all is good, holes are close enough to alignment to take screws - not perfect but nothing majorly problematic wrt fit. On closer inspection however there are a few issues to sort out:

Issue 1: Our old friend the standoff height issue (27mm TR-15T vs 25mm Dynastorm). Clearly I need to sort this as the CF is stressed as-is when i tighten down the battery holes. As I said previously I'm erring towards shortening the TR-15T parts by 2mm to resolve this.

Issue 2: Another old friend here, the servo's rod's path prevents removal of the stick battery pack. Again, I think the answer here is a custom shaped rod with a bend to clear the battery's left side. I've got something more substantial now in place for the servo link - a 3mm tapped aluminium tube of the right length (129mm) as opposed to the 2mm wire I mocked up with. Possibly I can just bend this tube to clear the battery and then use some longer adjusters to accommodate the longer path that the tube will be taking, if I bend it too far tho I think it will foul on the battery pin so it'll be a close thing.

I have a spare 129mm tube so I'll have a try at this at least. If not a CF plate should be possible.

Issue 3: This is one I didn't foresee - the Dynastorm battery plate pins are now situated too shallow to accept the DS battery strap. This is because on the DS the battery strap mounts directly onto the battery tray (with no 2mm CF top plate in between). I can see 2 options here. Either I cut the top plate further to allow the battery strap to recess to the original level (seems like a messy option) or I make new battery plate pins that are 2mm longer on one side. I have a micro-lathe so I think new pins should be fairly easy to machine, as long as I can find some Alu / Plastic stock to use.

No way the battery plate will fit under there as-is.

Issue 4: Battery pin hole alignment. I have a confession to make, I initially forgot to mark the battery pin holes on my template and added them at the last second. Looks like I misaligned them a bit. The pin fits ok when the top plate is loose but is very much stuck once the top plate is screwed down. I don't think this really matters - I'll just insert the pins before I put the plate on.

Barring the 3 issues that I need to sort out I think that is the majority of the build complete. Next step, solve the 3 snags above and then consider what to do with the bodyshell.

I've got one day off left until work re-starts for me. It'd be v nice to sort the mechanical bits tomorrow I think .

[novicelad 787]

Any updates @Ann3x?

[Ann3x 222]

6 hours ago, novicelad said:

Any updates @Ann3x?

Ask and you shall receive. Things have moved on. Ive just got a little distracted and forgot to post :).

Issue 1: The standoff height issue (27mm TR-15T vs 25mm Dynastorm). I milled down the TR-15T posts and also the TR-15T plastic end plate to 25mm. Now fits perfectly.

Issue 2: Battery clearance of steering rod. Bending the 129mm tube worked perfectly. Now clears the battery on loading and doesn't seem to soften up the steering actuation or risk the pivot ball popping off.

Issue 3: Battery plate pins are situated too shallow to accept the DS battery strap. I machined up some custom alloy pins on my micro-lathe. Was a bit of a hassle in fact as the size was too small to be comfortable. In retrospect I would have 3d printed the new pins but hey-ho - the alloy ones work fine.

Let's get Lathing:

They aren't perfectly equal as I was at the size limit for the lathe / my skills / the alloy i had and sheared a couple of trial pins. Shouldnt matter as wont be visible on the model and wont affect working.

Issue 4: Battery pin hole alignment. I'm just going to fit and forget. It isnt perfect but it works fine as-is, just means my battery pins are non-removable.

Left to do:

All fitted and basically "done". Still there are some things I want to sort out:

1. Im not happy with the rear tyres as-is. They arent close enough in looks to the Kingcab. Anyone got any suggestions?
2. Hi-cap springs are too soft for a monster racer. I've found a set of short hi-cap tuning springs to harden them up a bit - waiting for it to arrive.
3. Still need to sort a body. I may get a Stadium Blitzer soon anyway (to convert to Bear Hawk) so might test fit the shell. If not will consider a dyna blaster.
4. Actually run the thing (my achilles heel)

So here we are today with the current state:

Notice my 3d printed gear cover and slipper cover. Pretty.

I have too many projects atm. I also think im in avoidance on my painting, keep finding mechanics to do instead of getting on with it :).

[novicelad 787]

Looks awesome!

[Ann3x 222]

On 1/3/2018 at 8:33 PM, Ann3x said:

On goes the slipper which is *similar* to the dynastorm/blaster. Note the *similar* comment.... In fact there is one difference, the TR-15T clutch has 3 alloy spacers (circled in photo below) which seat under the clutch bolts. If you mount it with these installed under a dynastorm gear cover the clutch then fouls the cover (it took me AGES to work out what was causing the binding). I have no idea why the TR-15T has the 3 spacers as they seem to serve no purpose.... weird. Remove them and all is good.

 

 

For anyone interested I realised why the spacers and cap nuts are used on TR-15T. It's to retain the brake disk which would slip off without them.

Obviously that isnt required on an electric.

On 3/6/2018 at 9:07 PM, Ann3x said:

All fitted and basically "done". Still there are some things I want to sort out:

1. Im not happy with the rear tyres as-is. They arent close enough in looks to the Kingcab. Anyone got any suggestions?

Anyone got any ideas for some more King Cab like rear tyres?

I'm really not keen on the block ones.

[Ann3x 222]

So I took it for a trial run down at the beach with an old shell.

The good news was that the handling was really stable, pretty well balanced with steering and general handling but bad news was it was very slow. I took a vid after about 10m of running, voltage had dropped a bit by this point but was still not quick even with the fresh battery.

• 2s 4000MaH Lipo
• 21T Sensored Brushless Motor
• Speed Passion Reventon ESC (I just plugged the esc in and went, could it be throttled without extra config perhaps?)
• 19t 64dp pinion with standard DS gearing

Wasn't expecting a rocketship on 2s but.... kinda weak. Anyone got any ideas?