Twinwall ducting- what sort of minimum bend radius will work

[oldbutnotdead]

What it says really- burying some 50mm twinwall ducting between house and garage for comms, alarm and video cables and the best route to avoid uprooting 2 apple trees and faffing round a drainpipe is going to need a 90 degree bend about 2500 from the garage end of the duct.

The ducting is allegedly smooth internally- not quite smooth but certainly less knobbly than the outside. The supplied drawstring is very very skinny- that'll be getting replaced with some 6mm polyprop. What sort of bend radius will give me the best chance of cables not snagging while I'm pulling them through? Total duct length will be 28 metres- 24 of it in a straight line

Cheers

 

[ban-all-sheds]

What sort of bend radius will give me the best chance of cables not snagging while I'm pulling them through?

As large as you can possible create.

 

[333rocky333]

Do you have any drain rods, bend them and will give you an idea, then in the future if needbe you can at least know you can rod it

 

[bernardgreen]

Used plaited rope if possible instead of the cheaper twisted rope or use a swivel joint between cables and rope. Twisted rope tends to un-twist when stretched.

Using a twisted rope to pull in several cables and a replacement draw cord at the same time will end up with the cables twisting around each other and the new cord making any alterations at a later date very difficult.

 

[oldbutnotdead]

As large as you can possible create.

That occured to me as well while I was typing the post- 2500 looks favourite then

Do you have any drain rods, bend them and will give you an idea, then in the future if needbe you can at least know you can rod it

Good idea, I'll try that tomorrow when I'm back over there

Used plaited rope if possible instead......... swivel joint

Interesting and useful. I'm going to try and draw all the cabling through before I fill the trench in but who knows what the future will bring.......think I'm stuck with the budget twisted polyprop, haven't inspected it carefully but very good point about the twists.

 

[flameport]

10x the diameter of the conduit would be a reasonable minimum, so 500mm radius in this case.

 

[oldbutnotdead]

10x the diameter of the conduit would be a reasonable minimum, so 500mm radius in this case.

Ta- any harm in going bigger would you think? (I'll be doing this bit of the dig by hand)