Praga truck trial

[Abrs]

I personally quite like using silver solder - coz it's kinda pretty to look at afterwards

[Rob Reznik]

Hang on did i miss that? prop broke due to a bad weld? oh mr reznik please, lol !!!!!!!!!!!!!!!!!!

I apologise Mick - it was the metal that came away from the weld ;) .

[Ditch]

I saw this close up and it was definitely the bad metal pixies did the damage. Mick's weld was fine....... both bits.

[mrmmick]

love you guys lol

[Rob Reznik]

need to get a move on with the Praga and get it sorted - took the short prop ( 38cm's) to a prop specialist today hoping to get some advice on double cardan joints - alas they are not only expensive and the ones they had look weak but there didnt seem to be any more movement on them than the standard ones so possibly back to the drawing board - the other issue is there is not enough movement in the shaft and it keeps popping out so have to restrict the movement of the axle - anyone any other thoughts??? - still working on the steering and thinking about turning the front wheel stations around ( swapping sides) as this will protect the front brake chambers better and move the drag link pivots to the front where it will be easier to mount a straight solid link which will be pushed by a double acting ram - only disadvantage is that it will be more exposed but should solve this with a bash plate - also having problems getting the front tyres to stick out further forward than the chassis rails which I want to do to help drive up solid 90 degree banks

[zoltan]

Can you post any pics up of the prop? I had a good look at the forum meet but can't remember the layout now

[Rob Reznik]

will do tomorrow

[Rob Reznik]

think I may have sorted the prop issue out - here is the original - dont forget its only 38cm's long



it goes in here



but was speaking to the farmer today and he took me over to have a look at the Tractor rear PTO's which turn at 90 degrees although I doubt whether they will turn anything at that angle they are a huge improvement and think they will do the job




anyone forsee any problems?? - next question does anyone have one going cheap I could play with?

[paulob1]

sounds workable,,,a pto rotates at 1500 rpm...it must be useable...

did we progress the ownership by the club of the Praga at all...is this still on the cards...ie so that it can pay for its upkeep etc...I would happily donate a sum to its upkeep so that it can be made available for off roading weekends for club members...

[Rob Reznik]

nothing happening on that front AFAIK - still doing some more thinking on that matter - was thinking about flipping the front hubs around and having the link bar across the front linked to a double acting hydraulic ram and removing the two leaf springs and substituting them with one across the front like the older Scammells - would also be able then to move the axle further forward in front of the chassis/bumper making it easier to drive up banks - would need to add some link bars to the axle and a bash plate to protect the link bar/ram but should work - just need the time/money and parts - I have the enthusiasm though .

[paulob1]

are you still keen on the idea Rob...I will start a new thread and see if i can drum up interest...

[Rob Reznik]

no problem Paul - it will have to go in the end but as with all of them I want it right first .

[marcus]

Have used agricultural PTO shafts on my landrover as the original ones kept pulling apart! Home made ones are fine for offroading but would recommend a professional job for road use, prop judder at 85 mph in a series one is not nice If you are fitting a hydraulic ram for steering to restrict its travel to prevent snapping bits off just put some thick walled tube inside the ram unit, done this to a JCB steering ram on the landy about 10 years ago, 2600 psi and never a problem!

[Rob Reznik]

Took the Praga out for last run before she goes to her new home ;)

[youtube]http://www.youtube.com/watch?v=43K8sabN ... re=related[/youtube]
[youtube]http://www.youtube.com/watch?v=5-0OHQG4m2Y[/youtube]

http://www.rcscalers.pl/showthread.php? ... 1czony-%29

[Charlesm]

Very clever modelling and filming

[KarlJ]

I especially like the 1/10th scale blood stains on the passenger seat, very authentic ;)

[marcus]

So most of you will know now that the Praga of Death has a new owner


Here's us picking the POD up early this year

Dropped some batteries on and away it went

So my plans were
1 Modify props
2 Roll cage
3 Power steering
4 Front axle like my Scammell Explorer
5 Front difflock



First I purchased a rear axle from the Czech Republic for £220 brand new, the postage was conciderably more
Drilled the welds out of the diff housing and pressed the axle tubes out then did the same on the original front axle
Pressed the steering axle tubes into the locking diff housing remembering to turn the housing upside down so the front wheels turn the correct way



Remade the locking mechanism
Welded the axle tubes back in the housing
Next I made the whole axle pivot in the middle so no springs or chassis stuck out the front, just 10 inches of tyre


Mounted a hydraulic pump driven off the fan belts(not ideal) and a ram where the original steering arm went, without the springs the lock is much better now. Danfoss steering valve off tractor bolted to bulkhead and now can turn from lock to lock with 2 fingers Mounted hydraulic tank behind cab which knocked the bottom off the fuel tank at Halford

The props were quite simple just using the bits Rob provided with the truck



No vehicle is 100% perfect, maybe thinner tractor tyres would be better in the Halford clay

I also have all the bits now for the roll cage
Will make the diff locks air operated from in the cab
Transfer box jumps out of hi and low, do I repair or just buy a new one?
What vehicle do I buy now as Averill has taken custody of the POD

[Rob Reznik]

Nice work Marcus - that work on the front axle will have solved a lot of problems - reading through your work makes it sound like it was a 10 minute job but I know better !!! - did you replace the middle prop with the standard one which was shortened or did you fit the agricultural one? Those tyre pressures still look high - the biggest problem with the Wagtails clay is the tyres not cleaning themselves - if you watch some of the European truck trial videos you will see both poor and very good driving styles which are important on a big truck - momentum is crucial as well as trying to keep the wheels spinning and in some cases also moving the steering from right to left to help cut through.

I was also thinking about linking the axle breathers and maybe have them pressurised when going through water? - I would have thought 2-3 psi would do but maybe they are OK as is?

I never used the low ratio so didn't know it was jumping out - 1st is low enough in Hi so why replace the box? If you still want low I would suggest checking that it is fully engaging first - maybe its not quite in? Was it popping out while driving on the flat or did it come out when you were going over rough ground? - if the latter maybe the chassis was flexing and causing the linkage to move? - I had problems with the Clutch pedal sticking when the chassis was twisting.

The link bar (track rod) between the front two wheels is also weak - we bent it when hitting something on front wheel at speed and at an angle - straightened it by lifting truck with trolly jack on it but its something you may want to look at.

One of the leafs on the rear offside spring occasionally popped out of the hanger - you need to check this - also that rear cross member needs 'sweating' off and bolting on - my fault but it will causes some problems when you do some serious off roading!

Nice steering wheel - have you fitted any proper seats yet with a harness?

Anyway nice work - I'm glad to see its being improved on

forgot to ask - you still going to do more work on the Zil? ;)

[marcus]

Middle prop is my own design, works good but can still improve it. Have kept your seats but put in 4 point harnesses. I thought about pressurizing the axles, easy to do, also the bell housing, managed to fill it with mud whilst in my hole causing slippage when on full power. Didn't know about springs slipping out etc, is that covered in the warranty ;) As for the Zil, its not finished but they never are are they?:)

[Rob Reznik]

Any photos of the Prop? - also one of the pivot on front axle would be nice - wouldn't worry about the rear leaf popping out I forgot you don't drive it hard enough so will never have a problem ;) - how on earth did you get stuck in that small puddle