Thunder Model
British Scammell Pioneer
TRMU30/TRCU30 Tank Transporter 30 ton

Thunder Model kit 35200
Guide to modifying the front suspension/fenders to articulate
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Articulating front suspension/fenders:
The Thunder Scammell Tank Transporter kit provides a partial set-up for movable steering with separate stub axles (C51, C52) trapped between the axle jaws (these are moulded integral on the ends of the transverse elliptical springs) but when you fit the steering rods these fix the steering in position negating any movement, this is further compounded when fitting the fenders that glue to the outer axle jaws and also when fitting the steering linkages back to the main steering box. You can of course fix the wheels in any position you choose during assembly by gluing the parts in an offset position but to make a fully articulated steering set-up there are some modification needed to the steering linkages/rods and to allow the fenders to turn in unison with the wheels as per the real thing.

This guide will hopefully aid in achieving this should you want fully articulated steering for your model?

The front leaf spring is moulded in two halves (A7, A8) that include the 'stub axle swivel jaws' at either end and these are sandwiched together trapping the movable stub axles between them. You first need to trim the excess moulding tabs and small raised marks from the inside faces of the springs to get a perfectly flat mating surface so they will join flush. But don't glue the spring halves together yet as there are some modifications needed before hand.

Steering modifications:
The stub axles (C51, C52) have the steering arms included and the first step is to make the push-pull rod (A33) movable when attached to the steering arms.
First; Drill a 0.4mm hole in the ends of the push-pull rod and insert a 0.4mm wire pin, it's best to use wire as plastic rod or stretched sprue will not be strong enough take the movement stresses. Don't worry too much about the length of the wire pin this can be trimmed later, but about 3-4mm exposed will do. You then drill a 0.4mm hole in the ends of the steering arms, there is a recess used to locate the part to serve as a guide for drilling.

Next a 0.75mm plastic rod pin is added to the stub axles (C51, C52) that will extend up though the top half of the axle jaws. Note; the .75mm rod was actually closer to 0.9mm and I needed to drill a 0.9mm hole in the parts to take the so called 0.75mm rod. Drill the 0.9mm hole in the centre of the top rotating lug on the stub axles, make sure you identify the top correctly and drill a smaller pilot hole perfectly in the centre of the lug and then enlarge this hole via slightly larger drill bits until you get to the 0.9mm required, this will lessen the stresses during drilling preventing damage to the part than if you tried to drill the larger hole all at once. With the holes drilled glue the lengths of plastic rod with about 7mm exposed into the stub axles and leave to dry completely.

Stub axles and push-pull rod with added pins and holes as above
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You then need to drill a corresponding 0.9mm hole through the ends of the axles jaws to allow the pin to fit between the jaws and extend out the top, you have to drill this hole while the spring halves are separate so clamp these together and gently drill the holes again using progressively larger drill bits. With the holes drilled separate the spring halves and using a sharp #11 blade (or similar) clean out any reside from the hole edges to allow the pin to fit neatly, test fit the stub axle with pin as you may have to slightly widen the holes for the pins to move freely, this is easily done with spring parts separate using the #11 blade to trim the holes if needed? Note, drilling these holes will remove the small pin moulded on to fit the top steering arm (C38) but don't worry as the arm will be re-attached to the rod later.

Image of the separate spring halves showing the 0.9mm hole drilled while clamping the halves together.
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The two spring halves can now be glued together while trapping the stub axles between than and glue carefully to ensure no glue gets onto the stub axles and especially onto the plastic rod pin, make sure this moves okay while the glue dries. Once glued you can fit the two-part Perch Bar (A12, A13) and ball socket plate (C55) as well as the curved front axle (D12) with this assembly glued to the insides of the axle jaws. The fit here is very positive so there shouldn't be any fit problems.

The upper steering arm (C38) can also be attached but this MUST only be glued to the plastic rod pin, take care not to get any glue on the axle jaws in the process and check the stub axle and steering arm can still move freely in unison with the stub axle after attaching the arm, if any glue gets on the jaws just move the stub axle with pin back and forth until the glue loses it's 'bite' and moves freely. Note the arm should be set at 90 degrees to the wheel hub during this process and the plastic rod pin should extend about 3-4mm out from the axle jaws at this stage.

Assembled front suspension with upper steering arm attached.
Note the plastic rod pin extending out from the top of the axle jaws.

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The long push-pull bar (A33) can now be slipped through the holes in the Perch Bars and attached to the two steering arms by fitting the wire pins on the bar into the holes in the arms. To secure the pins I added a small thin card disc made with a punch & die with a 0.4mm hole drilling in the centre, this disc was secured to the pin with a small drop of thicker cyanoacrylate making sure not to get any glue onto the bars or arms, test to make sure they all move freely and then the wire pin can be cut down (I used nail clippers) and filed to remove any burs and make flush with the card disc, this clean-up method applies all subsequent pin attachments so I won't repeat this each time.

Underside view showing the small card disc holding the parts in place.
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Prepare the top steering arm (C38) by adding a 0.4mm wire pin to the outer end and also to one end of the connecting bracket (C40) while drilling a 0.4mm hole in the other end. Add a pin into the steering box (D23) by again drilling a 0.4mm hole and add the wire pin before gluing the box firmly to the chassis and allow the glue to dry completely and finally drill a 0.4mm hole at both ends of the steering push-pull rod (D26).

Rods and links modified.
Thunder Model

After ensuring all the stub axles/pins and arm move freely the suspension unit assembly can be attached to the chassis as per kit instructions and the steering linkages back to the chassis steering box can be attached.
(1) fit the pin you added to C40 into the hole at the end of the push-pull rod (D26) and secure with a plastic disc as before or whatever method you prefer but again make sure the parts move freely.
(2) fit the other end of the bracket C40 to the steering box D23 and secure in place again making sure it moves freely.
(3) fit the large bracket on the end of the push-pull rod to the end of the upper steering arm C38 and again secure with a card disc while again making sure all the joints move freely, it is most important you check each joint as you go to avoid and problems with glue getting where it shouldn't along the way.

Assembly as above.
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The Fenders:
Next assemble the fenders (A29, A30) to their mounting brackets (E18) allowing the dry completely, then note the locating pin on the bottom of the brackets, this has to be cut off and a 0.9mm hole drilled centring on the pin location. A word of caution here, the 0.9mm hole comes quite close to the edge of the bracket and you should hold the bracket tightly between stout tweezers while drilling to make sure the edge of the plastic doesn't distort or break while drilling.

Modifying the fender support brackets, note the fenders left and right are different sizes.
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On the actual vehicle the fender brackets are mounted on top of the axle jaws assembly allowing these to turn with the wheels and you basically replicate this with the modified fender brackets being glued to the plastic rod pin extending out from the axle jaws. Fitting this to the right side is easy as you have the upper steering arm in place so you can glue the fender bracket over the pin and onto the arm, but just make sure no glue gets to the jaws.

Attaching the right fender bracket as described.
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Attaching the left side fender is a little trickier as you have to fit the bracket to the pin extension but ONLY glue the bracket to the pin making sure not to get any glue on the axle jaws in the process. As the glue starts to 'go off' check the wheel hub moves along with the fender attached to the pin. Once you have checked that there is no glue in the wrong place leave to dry completely before testing the steering again but if all goes well when dry the steering along with all linkages/arms and the fenders should move a one as you turn the wheels.

Attaching the left fender bracket requires more care to not glue to the axle jaws.
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Once the glue has dried and everything moves you can trim the 0.9mm pin flush with the fender bracket for a better appearance and the wheels fitted to the hubs or left off till later in the assembly depending on your preferences?

Images of the completed assembly showing the wheels turned right and left as required with all linkages and the fenders moving in unison.
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Hopefully this guide will assist in articulating the front suspension/steering for those who wish to do so, this guide will be incorporated into the full kit review which will be posted shorty.
Note; the side 'back' and 'next' buttons are inactive but will be activated with the full review, thank you

Please note, the initial comments on the rear suspension were incorrect and removed after being on-line for about 30 minutes. If you had seen these please disregard what was posted, thank you.

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Army Wheels #AW18
Capricorn Publications
Pioneer: Scammell R100, SV1 and SV2, TRMU20 and TRMU30 in British Army Service
Warehouse Military Vehicle Datafiles WD3
Warehouse Publications
Scammell Maintenance Manual
and Instruction Book
Scammell Lorries Limited
The Military Scammell Illustrated
Lizzie & Pat Ware
Warehouse Publications


Page created 5 December 2017

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