Thursday, 18 August 2011

Good to go again! Just…

Finally got all the parts required to get the Savage X going again last night, so set to it right away to get it up and running.

As said before i had already received a new cover and back plate from HPI themselves but held out on a few other bits arriving from elsewhere to solve several things at once instead of breaking it down again.

Reinstalling a Cover Plate and Rotostart2 Back Plate on a Nitrostar F4.6

First of all check the spring loaded pin is in position in the centre of the con-rod. When i initially tore this down i didn't realise the pin was there and it shot out with some force! Luckily it didn't get far and i managed to retrieve it, and as a double bonus, the spring stayed put in the con-rod.

I also found the easiest method is to hold the truck vertically (with the back end upper most) this allows you to drop the pin in and not worry about it falling out or inside the engine somewhere!

And to make the next part easier, rotate the engine to bring the piston to BDC (Bottom dead centre), by turning the flywheel.


With the Starting Shaft located in the Cover Plate, position the slot/groove also at BDC as you will be applying this blind, the pin will of course locate into the shallow.


As you install the Cover Plate you will  need to tap it lightly to overcome the grip of the seal ring. Use something soft and blunt and only hit the plate itself, hitting the shaft will only transfer force into the con-rod and crank shaft and may damage something.

With the plate fully home, secure with the 4 cap screws and golden rule…


HPI Z159 (Green) Thread Lock is advised in the manual although anything equivalent should do the job. Also when using thread lock don’t squirt gallons of the stuff everywhere!

Even though i stress to use it, put a small amount along one edge of the full thread. Some people also advise to only dip the first 3-4 threads in. Either way it will create an ample coat across the whole thread as you install the screw. Putting too much in can sometimes effectively seize the screw and make it impossible to remove in future, or it doesn't dry correctly and therefore negates its useful properties!


I found turning a thread or 2 at a time on each screw helped to pull the plate in evenly, finished off with about a quarter of turn to tighten them up.

Next job is to add the Back Plate. This comes as a kit of parts with the screws and an Allen Key. It doesn't come with the gears, they will need to be transferred across from the old Back Plate unless they have been damaged.


I added a light film of moly grease to all the teeth and contact surfaces on the gears, best method is to just rub a bit between your fingers and then rub it all over the gears and the inside of the casing and bushes. Should keep it free running and protect against dust and water as when i opened up the old one its obvious this is not immune to contamination.


To finish off the Back Plate is assembled and fixed to the cover plate.

I started off by adding some Thread Lock to the supplied cap screws and noted straight away how much of a snug fit the holes are in the Back Plate to the screw threads. Most of the thread lock as a result was pushed back off the threads.

This made me wonder if this happened with the original installation and resulted in an inadequate amount of thread lock getting through to the Cover Plate and then working loose through vibration… although that doesn't amount the the failure of the material i admit.

Instead of the screws i applied the Thread Lock directly to the hole instead…

Not an easy task to try and squirt it in! Either use a thin sharp tool to smear some into the threads, or just apply to, and run the screw into the thread and remove it again.

Also don't forget to put the One Way Bearing (OWB) back onto the shaft and it must be the right way round! in this case the tapered end goes up against the cover plate.


Last but not last the Back Plate is added. Only three screws secure this, despite the provision for a 4th in the cover plate. This is due to the gear that takes the shaft essentially being in the way.

With the case being made of plastic its very easy to go over the top and start to crush the case if you tighten the screws too much.

I tightened them as much as “finger tight” would allow and then did a full turn of the screw. The screws bit into the plastic and gripped, but you don't get that reassuring feel that it has got hold of it fully! So don't go overboard…


Job done, i popped the glow plug out and gave it a spin with the Rotostart, and it works beautifully again!

Think the moly grease has been a worthwhile addition as it sounds much cleaner and smoother than before when the starter is spinning the engine.

Either that or it was due to it being loose before!

Happy with the repair, i got the back end bolted back up and did a test start with engine, took a few spins but eventually coughed back into life, happy with that result, it would be rude to not go out for a long waited bashing session!


Running great and huge fun all over again, started without a hitch on the first blip of the Rotostart, so it must have deteriorate over a (short) period of time as it was getting harder and harder to start and initially had me thinking my tuning had gone completely to pot!

And her comes the “Just…” as per the title!

After a couple of tanks, the Savage seemed to be struggling and loosing power… not what i want after just getting it going again!

On a few close up drive pasts, it appeared then engine was performing, but the drivetrain was failing to do anything substantial…

First thoughts were a fried clutch or the inevitable stripped gear! So i pulled up and took the body off and attempted an evaluation.

Thankfully pulling on the throttle revealed all there and then, the teeth were still present and the clutch was still doing a fine job, however the slipper was converting all the engines energy into a flailing mess of nothingness!

It was so slack you could turn the gear with your finger and it would slip… so… back home i went!

I stripped the top of the gearbox and reset the slipper spring… it did seem to have loosened off slightly, so i set it back to the HPI recommendation of tightening it all the way and backing it off one half turn and it did start gripping again. However inspecting the Clutch Pad did show some significant wear and deterioration, I'm wondering if it has been a bit too loose on a half turn and wearing itself out too quickly?

A quick test run showed it was still able to perform, but does seem a bit groggy, so I've ordered some new pads for when it finally lets go completely!

Hopefully will get them for the weekend or it will at least hold out as with a bit of luck ill be off for a bashing session in an old quarry!

Saturday, 13 August 2011

Roto-fail Update 2

Double happy today! Woke up to find a jiffy bag on the door mat containing the replacement parts for the wrecked cover plate and case.

Exceptional service from HPI UK i must admit.

The parts i received are…

  • HPI Part No. 87119 (Case for back plate unit)
  • HPI Part No. 1426 (Cover plate)


I am excited to get these fitted and have the truck back up and running, but forcing myself to hang fire while other items arrive from elsewhere. Mainly I've got some thread lock and lubes on the way to ensure a proper job and hopefully stop it from happening again.

So sadly, looks like no Savage action this weekend…

On another plus note i did receive a reply back from Horizon Hobby regarding the lack of length to the telemetry sensors for the SR3300T.

Sadly it was just a rep from the company sending me a link to the HH online shop for telemetry extensions… which are too long and don't appear to have the same type of connectors.

Shame that, so I've decided i will speak to friends in the know when it comes to electronics and get the wires extended by other means.

Friday, 12 August 2011

Roto-fail Update 1

After the last post i set about working out what would need replacing to get the Savage up and running again.

Thankfully the instruction manual has a nice comprehensive list and diagrams showing what goes where, and all labelled with the part numbers.

15 minutes later i had worked out what i needed and got it ordered online through Apex Models.

At the same time i sent a message to the Technical Services team at HPI UK, mostly asking advice on how to prevent it happening again.

I went to check my email this morning and had already received a response back from their team asking for a bit more information and some pictures of the damage. So i promptly sent a copy of the images seen in the previous post and within 10 minutes i had received another response saying they would replace the cover plate and back plate!

Very pleased with that and a double thumbs up for the team at HPI UK!

Just wish i had touched that base first instead of ordering new parts! But at least ill have a set of spares should something else happen in future.

Thursday, 11 August 2011


After raining most of the day and thankfully, clear skies by the time i got home, i thought it would be rude not to get out and play in the puddles and vegetation and make some nice big muddy splashes out in the field!

Happy as a pig in…., well, mud. The Savage was having no bother dashing through water logged potholes and providing entertainment with huge power slides over the wet grass.

As light levels started to drop, i was contemplating returning home but still had a half full filler bottle so thought i may as well polish that off to draw in a close to the evenings antics.

As i returned to my “pit area” i noticed a sort of “flapping” noise coming from the truck.

I carried out a few low speed passes and sure enough the noise continued, so i went in for a closer inspection, assuming a twig or something similar had got stuck underneath or in a wheel etc.…

As the truck pulled in, it coughed and stalled. In my wisdom of trying to suss the noise out i hadn't paid attention to the already bone dry fuel tank.

So i topped off with the fuel i had left and grabbed the Rotostart and Ignitor to fire it back up.

However when i tried to engage the rod with the starting block, something was clearly amiss. From the limited view i had inside the back of the truck it was clear that something had come loose, namely the block itself.

I decided to give up there and then and just loaded the Savage and my gear into the back of the car and headed off home for a full detailed break down.


The initial view i had was as follows, there is clearly a void between the engine and the starter…


With the fuel tank removed it was now blatantly obvious that the starter had indeed come away from the cover plate!


I was fearing an engine out job, but remembered the whole tail end of the chassis can just be unbolted, which is very easy and straight forward.


Now i could asses the damage…


Sure enough… completely void of any mounting screws!


Simply loose and removed by hand…


Damage had occurred on the starter casing with two of the lugs showing cracks. Luckily the plastic was damaged but not sprained, so i applied some super glue and allowed it to wick into the cracks. Hopefully taking hold and should make a strong bond.

In my usual manner i did manage to glue myself to everything else too!


I stripped the starter down to inspect any other damage. Luckily the gears and bushings still looked in good condition.


If the repair is a total failure… then its on to getting replacement parts. For one i need some new cap screws to replace the missing ones.

And this is where it gets worse!

My first port of call was to check the mountings to see if they had just made a bid for freedom or sheared in the cover plate.

Unfortunately the cover plate had other ideas…


Yes… two fracture points through two of the threaded mounting holes…

How long it had been like this i have no idea! Could have been like it from day one, and the remaining screws have just given up the fight.

I have a hunch this happened when the truck was built, and inferior materials may have also been a factor. Whoever constructed this truck/engine may have applied too much pressure to these screws and caused the metal to fail.

I would be highly surprised if this has happened through usage of the truck over the last week, as that area is exceptionally well protected!

Next job…. scan the instruction book for part numbers!
Ill also contact HPI to see what their take is on the matter.

Wednesday, 10 August 2011

HPI Revolution

So HPI have released a teaser showing a 1/8th scale petrol/gasoline powered monster truck, due for release sometime in 2012?

Should be very interesting!

And i think my bank balance might need to be at a suitable level come release day…


Tuesday, 9 August 2011

HPI Battery Level Indicator

Over on the Info Site i have added a page for the Battery Level Indicator option.

HPI Part Number: 308

HPI Battery Level Indicator

Bashing and Tuning

Despite the high winds last night the overwhelming urge to get out and play had me on the windswept waste lands again. This time the over half came along to get a bit of practice in photographing the Savage in action (pictures to follow soon).

In the mean time i had all intention to start tuning the F4.6 engine and get it running at full power. Sadly i shot myself in the foot after looking at the gauge for the receiver battery level and noting it to be in the first yellow marker LED, and like a tool i thought, “that will be ok”.

After a tank and a half of fuel the truck started to struggle, especially with throttle control, and i quickly twigged on that the servos were struggling to operate their designated systems, followed shortly by the DX3S informing me of a low receiver battery condition.

Inevitably the failsafe's locked the whole thing out and left me stood there feeling like a class-A fool!

Lesson learnt: charge the battery or obtain/carry a spare!

I did get a short way on tuning though, doing the norm and turning in the carb needle, checking temps, and with every following run the truck is getting faster and more brutal on the pickup. I can see why they named these trucks “Savage” now!

On the DX3S telemetry front, sadly no response from Spektrum yet, although they do say they respond within 3-5 business days.

So i attempted a temporary fix for the temp sensor…

It basically involves attaching the sensor to the side of the block with a tie wrap! A bit crude, but the sensor is technically in the right area, bar it being vertical rather than horizontal that the normal loop wire would position it.


This is followed by running the wire into the receiver box and attachment to the roll bar to help keep it out of harms way…


Thankfully it works and reports temps back to the radio, and comparing it to the infra red gun i have for the glow plug temp its pretty consistent with 3-4 degrees of what the temp gun tells me, so works well as an on the fly check in case anything gets too hot, too quick.

Anyway, battery’s are on charge and ill be prepared properly next time!

Bonus mud plugging shot!


Monday, 8 August 2011

Spektrum DX3S - Update 1

With the arrival of the Savage X, no short work was made of removing the installed radio equipment from HPI.

I was thinking of testing the capability of the RTR equipment, but i really wanted to get my hands on using the DX3S, no bother, ill perhaps test it at a later date.

A big bonus with the DX3S is the inclusion of the 3rd Aux channel as i had intended from day 1 to install the Reverser Module to the Savage.

The Reverser Module comes in 3 flavours…

  • HPI Part #87000 - Module + Servo + Mixer
  • HPI Part #87039 - Module + Mixer
  • HPI Part #87032 - Module ONLY

In hindsight I've worked out i could have purchased the module only and a 3rd servo as an individual item as the radios Aux channel takes over from the mixer.

Plugged into the receivers Aux port, the Aux switch on the radio switches between the hi and low position of the servo, which operates a sliding “lever” to engage the reverse idler in the gearbox.

Normally on a 2 Channel system the mixer would be employed, and the method is to hold the brakes for 4 seconds and the mixer flips the 3rd servo to engage reverse or vice versa. This in its own right is a minor safety system, due to the fact that the truck will be at rest without fail when the reverser engages. Running on the Aux channel does allow you to flip the switch whenever you feel like it, and to be honest i have caught it once or twice already before being completely at rest and have “crashed” the reverser! Luckily no damage, but a lesson learned to be a bit more careful.

The DX3S allows you to adjust the travel of all servos and this has been especially advantageous with the Reverser, as the construction of the control rod does not give it any nominal size or length. So i was finding that in the reverse position, the servo was attempting to pull the rod too much and was working hard against the “shock absorber” which basically consists of two small pieces of silicon fuel tube that are limited by two brass clamps. As a result the servo was jittering under the strain. Thankfully backing off the low travel down to 50% allows it to full engage the reverser and not have any problems. Result!

Another of my main interests with the DX3S and combine SR3300T receiver is the telemetry system, so i have indefinitely made a beeline to get this installed.

Unfortunately i ran into several problems when i attempted to get it fitted.

First and fore most the RPM Sensor mounting kit doesn't fit the Nitro Star F4.6 out of the box.

The first problem being, one of the two mounting plates with adequate slot spacing, is too long. With the sensor mounted it butts up against the Rotostart2 plate and the flywheel…


Thankfully not too much of a problem as the mount is made of aluminium, so is easy to cut down to size with a hack saw.

With about 5mm removed from the back end of the mount, there is then sufficient clearance between the sensor and the back of the flywheel, but another problem is then found where the small circuit board that the sensor is mounted on, and due to its shape, now pushes up against the crank case. Causing it to stand off from the back of the flywheel and not be in view of an applied decal attached to the flywheel face.

It is possible to turn the sensor board upside down, whether this will still work or not, and as a result the shape of the board allows it to move in closer, but i was now faced with the sensor being too high up, and once again not in view of the flywheel.

For now i decided to have an A-Team moment and attempt to create a mount from the available pieces to make it work.

This involved cutting one of the others down and attaching it to the main plate in order to keep it the same way up, but lower it down.

This helped but i don't believe it has gone far enough, and i don't have long enough screws to go any further, so this will be a future development.

Here is the final sensor mount, the insulation tape is to protect the contacts on the back face of the board shorting with the metal.


And here it is mounted on the side of the engine…


The next upset with this, and the fact that you can see the connection wires tie-wrapped to the chassis may be a bit of a give away… they don't reach the receiver box!

There is not much in it, but sadly not enough to allow an easy electronics install without having to do unnecessary and extensive work to the radio box, or fearing the wires getting snagged in the slipper or clutch pinion teeth.

So the next idea with this is to get an extension lead or just go ahead and extend them myself with some normal multicore wire. I am currently awaiting a reply back from Spektrum themselves on which way to go about this.

Second to this, the head temperature sensor is also in the same boat. With a nice simple method of a loop wire being wrapped around the bottom of the cylinder head, which also contains the sensor component itself, is simply clamped up by pushing a couple of silicon toggles along the wire loop to hold it still. But unfortunately this is also too short… a shame as the temp sensor was the most interesting element.

The wire for this sensor also feels much more sturdy, so I'm thinking it may be K-Type wire(?) so before i go ahead and look at modifying that i will await Spektrum's reply on the matter.

HPI Savage X Arrival!

Finally last Friday the first of my new fleet arrived in the shape of the afore mentioned HPI Savage X.

Between now and then i have spent most of my time stripping various parts of it down and installing improved and/or upgraded components after various research, this mostly consists of the Spektrum radio system, the 3 speed conversion, reverser module and some of the standard plastic bushings swapped out for bearings, ill comment more on these items at a later date.

As for running the model, due to a few social events over the weekend i haven't ended up with the time i would have liked to get it fully run in and tuned up.

The most i achieved was getting the static break in done (as per HPI’s recommendations) by running a couple of tanks with the car up on stands, and then spent half an hour mainly crashing into the flowerbeds while setting up the servo travel on the back garden, eventually this prompted the girlfriend to suggest i pack it up shortly as to not annoy the neighbours with the noise! Honestly though we do have elderly neighbours and i admit its not nice to annoy peoples afternoons with what sounds like a very angry swarm of bees!

Thankfully i do have an area not far from where i live with a nice expansive amount of waste land, well out the way of any residential areas to make as much noise as i want, so that was the next port of call.

Armed with only a couple of bottles of fuel, starting gear and my temp gun (as i had one of the social gatherings looming… taking too much fuel would have meant me never making it!) i proceeded to drive around at half throttle and just start to get everything loosened up.

The truck started effortlessly with the Rotostart2, and fires within a couple of seconds when there is enough residual heat in there. The last nitro models i had were all pull start, and i don't miss them one bit!

Although running very groggy due to it running super rich on the factory break in settings, i can see this is going to be major fun when its fully up and running. Even running very slow with only a slight squeeze of the trigger i had small amounts of air off reasonable mounds of earth and had no trouble battling through grass and brush that was roughly 2 feet deep, the Savage just powered through the lot of it.

Anyway, here is a few pictures of it in its brand new state of glory, before it gets beaten and battered!



All very nice and shiny new at that point! Might as well admire while still possible!

My only criticism at this point is the completely exposed underside of the Savage between the twin chassis plates, mainly the exposure of the brake discs to the elements and ensuing debris that will be dragged beneath the car and ejected from the tyres, I've already noted since starting that it that they get readily sprayed with 2 stroke oil and fuel that's made it through the exhaust.

I may look at custom fabricating a “bash plate” from carbon fibre for a bit of increased protection as a result.

I also bought a set of Phaltline tyres (and a set of sway bars) for a bit of car park bashing when i get the chance.


And to sign off for now, just a couple of pictures of it after the first session last night, will hopefully be getting some action shots and videos in the near future.