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Thread: My HG P407 Story

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Old 03-05-2019, 02:24 PM   #1
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Default My HG P407 Story

Firstly its probably best to start at the beginning about 35 years ago , I was 14 then and deeply into off road racing but one Tamiya model did catch my eye , the Toyota 4x4 Pick Up or Hi Lux as its commonly known , i was always in awe of its scale detail but we laughed at its rigid suspension and poor off road ability ,those things and the price put me off . Now the years spool by to the present day and after nearly a 30 year brake I'm back into RC cars , mostly restoring vintage off road racers but I've increasingly been drawn to watching youtube clips of scale crawling and i started to wonder if I'd enjoy a change of pace .
This is when the HG P407 came to my attention and the boxes started to get ticks in them .
A good scale look.
Leaf spring suspension .
Three speed gearbox .
Lots of upgrades intended for the Bruiser already on the market .
So in January one arrived on my doorstep and the journey began and my plan from the off was to create the best crawler i could from it on a fairly tight budget .
My initial thoughts were WOW! you get a lot for the money , then we move into what it's faults are .
Faults
1 The shocks leek badly
2 The suspension is over sprung
3 The tires are too hard
4 The steering has too much slop
5 The suspension has little articulation .

The shocks
Right at the beginning i was in two minds as to weather to replace or rework the leaking shocks , the first thing i did was fill them with 15WT oil , the damping effect was so strong that instead of the piston passing through the oil it instead just popped out the floating constant volume cap ! so i began by filing two flat sections on the side of the piston heads , i carried on until i got the damping effect i wanted .
Next was to address the leaks , they leaked at both ends ! so i started at the floating cap end first , what they had done was cut too deep a groove for the O ring meaning there was no seal at all ! out with the plumbers tape , removing the O ring first i wound some plumbers tape into the bottom of the groove , a little trial an error and i had a good seal once the O ring was fitted . The shaft seal came next , inside the screw on cap there was a washer a plastic spacer and an O ring , the washer was meant to slightly compress the O ring but the washer was to wide a diameter to fit into the recess for the O ring so it gave no compression at all , a quick rummage in my spares and i found some spring washers that would fit perfectly and also offer a little more compression to the O ring , it worked ! so i now have working shocks .
Now I'll add this here but i actually did this a lot later , the shocks have two additional problems , the first is the coil spring that goes over the shock shaft , why ? the leaf springs are so stiff already ? but that's only half of it , when the suspension is compressed the coil spring closes up and limits travel ! so ditch that coil spring ! Lastly at the bottom of the shock it attaches to the axle with a stepped metal sleeve and a screw but that sleeve does not allow much articulation at all , out with the Dremmel , what i did was open out both sides of the hole in the shock cap to make a conical hole only leaving the center of the hole uncut , this allows the stepped sleeve to pivot in the hole .
The bottom one has been opened up.

The left one shows the increased articulation , in fact more than shown .


The Springs
The springs are very stiff , I've already suggested you ditch the coil springs from the shocks but that has little effect so we also need to remove a leaf from the pack , at the front i remover the shortest leaf and at the rear the middle length leaf , while at it I also did the Chino mod , this is where you use a grinder to taper the ends of the leaf at the eye bush so it can pivot in the shackle . This i found gave me the best articulation and suppleness all round .
Again I did this later on but I'll throw it in here as it makes it tidier , the U bolts that secure the leaf springs to the axle have the threaded end and nut's at the bottom , this reduces clearance and offers another place to snag on so I made up a new set from M3 studding , heating the studding and bending it around a 10mm shaft , when fitted they are facing upward not down as shown .

I did this at both ends , it does mean you loose the front diff skid plate but i never liked it any way as it just looked out of scale .

Tires
The tires are just too hard and not a nice scale tread pattern in my view , i saw on another forum that someone had fitted Austar AX -3021 tires , very cheap so i ordered some and so far I'm really happy with them , much softer and a nice scale looking tread pattern .


Steering
The steering slop is a heritage thing , just like its sire the Bruiser its an awful setup so a front high torque servo mod was in order .
I did my own take on the front servo mod , moved the front shocks behind the axle at the bottom and top , for the top mount I used the front screw hole for the gearbox mount cross member and there is a hole for the old steering pivot assembly that just needed elongating a little to line up , strangely the hole for the steering pivot is on the other chassis rail as well ? So that just needed elongating a little as well the bottom already has a mount for the shock behind the axle .
Then I moved the L section steering arm from the left facing back to the front on the right knuckle .
The front cross member already has two threaded holes in the top of it so I used them to mount an L section piece of aluminium on top and over the back for mounting the servo , this mod only requires two holes in the chassis rails to be elongated to fit the top shock mounts otherwise its already there , all you have to make is the servo mount and a track rod , the rest is just nuts and bolts .
I'll post pictures tomorrow .





I got even luckier with the servo lead , I thought I'd have to extend it but because of the Y harness for the lighting system I had just enough length

Last thing mechanical that i though needed changing was the motor , so i fitted an Absimma 55T motor and I'm very happy with it .

So that's all the technical stuff so lastly the cosmetic stuff , the body was treated to a distressed look by adding rusty sections using the salting method , the interior got painted , i made some internal door panels and installed Shaggy and Scooby as driver and co driver.The body also got a full lighting kit with working indicators , brake and reverse lights .













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Old 09-14-2020, 03:15 PM   #2
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Default Re: My HG P407 Story

Been playing again , as anybody can tell you the Bruiser / P407 don't flex well and although you can get satisfactory articulation up front the rear end is another matter , the rear just don't twist and to my mind looking at it it's down to the wider position of the leaf springs , this gives less leverage on the spring compared to the front , so I've had it in mind to try and moves the leaf springs it a bit at the back , there are a few barriers to doing this , firstly the bottom lid to the servo housing is in the way of where you want the front mounting for the leaf spring to be so i modelled it up and redesigned it so give enough space for the front mount and spring , in the pictures the lid I've printed is white , this makes it easier to see hopefully but it wont stay that way .


very rough and ready for now and I've refined the lid shape but its not finished printing the new version , the longer bolt through the far side of the shackle is surprisingly secure , at the rear i printed a spacer to move the rear mount in as well


The result is quite a bit more rear flex ,ideally I'll relocate the shocks as well but for now its still much better.



that blue box is 4.5" or 11.5 cm , I've only had a very short test drive but you can now really see the rear end articulating Oh almost forgot the new lid has more clearance for the rear prop shaft as well as that was fouling on mine even before i made this mod .
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Old 09-19-2020, 11:43 AM   #3
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Default Re: My HG P407 Story

I've had a chance to give this a bit of testing and i am very pleased indeed , the rear now flexes almost as well as the front and this has a very pleasant side effect , before all the flex was up front and i always had tires rubbing the body but now that half the flex is at the rear its stopped the rubbing ! half an hour testing over rocks and obstacles and i never heard that annoying pooping rubber noise of tire on body once !
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Old 12-08-2020, 09:28 PM   #4
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Default Re: My HG P407 Story

Hi there!

I know this is an old post but I just ordered one of these trucks for Christmas and plan to follow your modifications guide.

I was wondering if you still have your 3D printer STL files so I can print the components you designed in order to relocate the rear leaf springs?

Thanks

Mario
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