RcTek : Information & Resources for the Model Car Racer

PB Racing Dart - SVM Columbia Mark 5 Competition Clutch

We have tried and seen various modifications to the standard Dart clutch but decided to take a more drastic measure in order to have a clutch that offers minimal maintenance and a fair degree of control.

Click on any of the images below to see a bigger version.

Note: This article was first published in 2001 and needs updating as the parts may not be still available.

SVM Columbia Mk5 Competition Clutch

PB Racing Dart fitted with an SVM clutch

PB Racing Dart fitted with an SVM clutchPB Racing Dart fitted with an SVM clutch

We have successfully fitted an SVM Columbia Mark 5 Competition clutch to our Dart after studying the Radiosistemi car already in our possession. All parts were supplied by Alro Racing Systems, whom we thank for their expertise.

Please note that this modification was only made possible due to Rear Outboard Brakes being fitted to the car.

The actual fitting of the clutch was fairly straightforward with only a small amount of material needing to be removed from the side plate and the chassis. Also required was an adapter to hold the spur gear in place as the clutch and gears have been moved in by some 19mm.

The Chassis Cut-out

PB Racing Dart fitted with an SVM clutch

The image shows the cut-out that was made in the chassis, which was 10mm deep to allow for sufficient clearance for the spur gear.

The adapter for retaining the gear is also clearly visible, which is discussed below.

The Side Plate Cut-outs

PB Racing Dart Side Plate

PB Racing Dart Side Plate Cut Outs for SVM Clutch

The side plate (left) had to have the corners cut away (right) so that the clutch bell could be fitted into place.

Although this has weakened the mounting points for the engine, the forces generated by the gears are not in the vertical plane and so should not present a problem as long as the set screws are kept properly tightened.

We may add a diagonal brace to one or both of the top mounting holes in the engine just to be on the safe side of things.

The Adapter

PB Racing Dart spur gear adapter

As the SVM clutch is far nearer the engine than the original PB clutch we had to move the gear carrier (# 73/235) in to match the new position of the pinion. Rather than cut down the layshaft, we made an adapter that slides over the exposed end of the layshaft, which allows for the PB clutch to be refitted if necessary.

A new locating point has to be put in the layshaft for the grub screw in the gear carrier. This can either be done with a grinder or, as the layshaft is not hardened, a drill.

The combination of the set screw and nylock nut does not require any threadlock. The set screw is long enough to ‘bottom out’ in the threads in the layshaft and the nut locks the gear in position.

SVM Parts Required

SVM Competition Clutch BellSVM Competition Clutch Adapter

SVM Competition Clutch

The SVM Columbia parts you will require are the Adjustable Competition Clutch (# S5325), which is shown to the right.

The 26T pinion (# S5355) is only available as an alloy screwed on type and is shown in the image to the left with the corresponding clutch bell (# S5360).

The clutch nut, which is shown on the left can be bought as a one piece standard item (# S5112) or a two piece Racing Clutch Nut assembly (# S5112A).

Also required are two of the Clutch Bearings (# S5040) and a circlip to retain the clutch bell.

The screwed on pinion gear does not need any threadlock on it for retaining purposes as it self tightens in use.

The springs in the competition clutch should be slightly compressed before assembly.


This modification has been tested and makes a significant improvement to the Dart as there is no ongoing maintenance to consider. We will be drilling a hole in the clutch bell to make adjustment quick and simple, although caution must be exercised as the steel is hardened.

A 28T pinion (# S5356) is available and should fit, although this has not been tested.

Because the clutch is further in, there is now room to move the engine sideways in order to better balance the car up, should the need be felt.

Please feel free to submit your own tips/modifications and thoughts to us.

Update — December 2008

The SVM clutch didn’t stand up well to competiton/abusive use and the shoes wore rather quickly and I will be reverting to the standard PB version.

Related Information

Standard Dart Clutch Modification

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© 2001, 2009 by Darren Burnhill