Motor retainers

Brand
Diameter
Motor diameter (mm)
Hazard type
Dimensions
Inside diameter
Motor mount
Outside diameter
Rocket length
UN Classification
Weight
In stock
Type
Quantity in pack
Price

You need a system to retain your motor in it's mount. Some motor mount kits will include this, however some won't and if you're making your own from some motor tube you will need to ensure the motor doesn't escape (either way).
A thrust ring at the front of your motor tube, and a retaining system at the rear should work great.
You can choose engine hooks that hold the motor in place, or motor retainers that screw into place. 
You can even make a 29mm mount and use adapters to have the option of using both 24 and 29mm motors too, although this will add some weight. 

 
BrandEstes TypeEngine hooks
Stock: 6 item(s)
£265
+
 
BrandKlima Length68mm Quantity in pack6 TypeMounting brackets
Stock: 24 item(s)
£750
+
 
BrandEstes Diameter24mm Hazard classNot dangerous goods UN ClassificationNot dangerous goods Quantity in pack2 TypeMotor retainers
Out of stock, contact us.
£799
 
BrandEstes TypeMotor retainers
Stock: 4 item(s)
£669
+
 
BrandEstes TypeMotor retainers
Out of stock, contact us.
£3569
 
BrandLOC Precision Diameter29mm Hazard classNot dangerous goods Motor mount29mm UN ClassificationNot dangerous goods Quantity in pack1
Stock: 10 item(s)
£976
+
 
BrandLOC Precision Quantity in pack2 TypeMotor retainers
Stock: 27 item(s)
£260
+
 
BrandKlima Diameter18mm Outside diameter18mm Quantity in pack6 TypeThrust ring
Stock: 23 item(s)
£210
+
 
BrandKlima Diameter23.8mm Dimensions23.8mm x 6.7mm Inside diameter18.6mm Length6.7mm Outside diameter23.8mm
Stock: 2 item(s)
£4189
+
 
BrandPublic Missiles Ltd Diameter29mm Hazard classNot dangerous goods UN ClassificationNot dangerous goods Motor diameter (mm)29mm Quantity in pack1
 
BrandBlackcat rocketry Inside diameter29mm Motor mount29mm Quantity in pack1 TypeMotor retainers
 
BrandBlackcat rocketry Motor mount29mm Quantity in pack1 TypeMotor retainers
Stock: 4 item(s)
£1792
+
 
BrandBlackcat rocketry Diameter24mm Weight9g Quantity in pack1 TypeMotor retainers