Prop catcher
loggyboy - 22/1/12 at 11:19 PM
After seeing a few minor horror stories of props letting go, thought id make one up for mine. Infact, i decided to make 2, 1 for each end. This meant
I didnt have vertical members to mount on so came up with this template:
Was fairly happy with that so set out making it.
The steel I used is quite thin (1.5mm ish) but due to having the circular ring I felt that its really only ever going to guide the prop, and due to
being fairly well contained forces would be minimal, and should certainy allow me to come to a stop before it destroyed itself.
One side of my steel sheet was very rusty (untread peices on left), so some 'green gel' helped out, followed by a good rub down.
And just some lightening holes to make me feel better about adding weight!
Whatta ya think?
Just gotta add some rivnuts to the chassis to mount it on, then powder coat, and make the 2nd one for the front, but that will have to wait till the
gearbox is in so i know where it needs to be located.
[Edited on 22/1/12 by loggyboy]
A1 - 23/1/12 at 02:15 AM
off topic, but see that drill youve got... ever had a problem with them? ive had two now where they go onto overload mode and stop having any speed
variability. bit of a pain.
i like the prop catcher though! puts your mind at ease a bit 
designer - 23/1/12 at 07:02 AM
That's a good job.
Personally, I'd only put one on the front, despite what is said on here, because if the UJ's are well maintained the one that will
let's go is the front as it is the one taking mist stress.
MikeRJ - 23/1/12 at 08:34 AM
quote:
Originally posted by designer
That's a good job.
Personally, I'd only put one on the front, despite what is said on here, because if the UJ's are well maintained the one that will
let's go is the front as it is the one taking mist stress.
Why does the front one take more stress than the rear? Both take the same amount of torque, and any articulation should be very similar.
Irony - 23/1/12 at 08:59 AM
Personally I'll be making 2 but I think if I was making just the one I'd put it on the front. I have visions of it coming off a jabbing
into the ground at speed and punching the rear of the car upwards........
Thinking about it.... what is the problem with making just one and putting it in the middle. The chances of both ends of the shaft coming off are
remote.
loggyboy - 23/1/12 at 09:06 AM
quote:
Originally posted by Irony
Thinking about it.... what is the problem with making just one and putting it in the middle. The chances of both ends of the shaft coming off are
remote.
I did think about that, but due to the clearance left (Mainly down to my poor manufacturing tolerances!), I felt that the angles left if there was
only a central one, the prop could still move a fair amount. As the tunnel is quite narrow the loom, brake and fuel lines could still get caught,
where has having 2 the movement is limited to the amount of gap ive left only.
designer - 23/1/12 at 09:16 AM
The front UJ takes all the initial 'shock' force so, if both are in the same condition, it breaks first.
Putting a prop catcher in the middle will let the prop flail more and trash any steelwork, pipes, wires, etc.
[Edited on 23-1-12 by designer]
40inches - 23/1/12 at 09:26 AM
I have one fitted, simple but effective.
Prop Catcher
loggyboy - 23/1/12 at 09:38 AM
quote:
Originally posted by 40inches
simple but effective.
Has it been tested then? or are you just hoping so?
(not saying that it isnt/wont be - just wondered!)
loggyboy - 23/1/12 at 09:45 AM
quote:
Originally posted by A1
off topic, but see that drill youve got... ever had a problem with them? ive had two now where they go onto overload mode and stop having any speed
variability. bit of a pain.
Been fine for me. Got it last Christmas for about £80 (maybe 60? i forget) from B&Q, came with 2 batterys and it seems to be working well, done
plenty with it too.
adithorp - 23/1/12 at 12:07 PM
quote:
Originally posted by Irony
Personally I'll be making 2 but I think if I was making just the one I'd put it on the front. I have visions of it coming off a jabbing
into the ground at speed and punching the rear of the car upwards........
Thinking about it.... what is the problem with making just one and putting it in the middle. The chances of both ends of the shaft coming off are
remote.
The main danger with a broken prop is it flailing around not sticking in the ground. That tends to take out the rear loom and fuel lines and in a few
cases, the tunnel panel and even chassis tubes... and then your ankles/arse! The prop catchers job is to restrain the prop as close to in line as
possible. As long as it's inline then it just spins and doesn't need the catcher to be very strong. Putting it in the middle increases the
angle that a broken shaft can move out of line and the amount of flailing.
MikeRJ - 23/1/12 at 12:22 PM
quote:
Originally posted by designer
The front UJ takes all the initial 'shock' force so, if both are in the same condition, it breaks first.
Think about this: if the rear UJ was disconnected how much torque would be put through the front UJ? Only the amount required to actually accelerate
the mass of the prop itself which is tiny in comparison to the loads required to move the car.
scudderfish - 23/1/12 at 12:42 PM
quote:
Originally posted by Irony
The chances of both ends of the shaft coming off are remote.
If both ends come off, you don't have to worry about the prop flailing into your thigh as it is 50m up the road behind you
roadrunner - 23/1/12 at 01:00 PM
I think this is an easy job worth doing.
I will do mine this winter while the engine swap is ongoing , it will be easier to do.
Nice job by the way.
And if all thought about bad things happening while we are driving, we would never get off the drive.
Brad.
matt_gsxr - 23/1/12 at 01:07 PM
How are you going to attach the prop catcher to the chassis?
If you weld it then will you ever get the prop out again?
loggyboy - 23/1/12 at 01:43 PM
quote:
Originally posted by loggyboy
Just gotta add some rivnuts to the chassis to mount it on
Rivnuts, 2x m5 on the 25mm bottom rails, and however big ones I can fit on the smaller 19mm rails on top.
foskid - 23/1/12 at 02:21 PM
quote:
Originally posted by 40inches
I have one fitted, simple but effective.
Prop Catcher
I like that one, Afraid I'm going have to plagiarize that I hope you don't mind.
40inches - 23/1/12 at 02:46 PM
quote:
Originally posted by foskid
quote:
Originally posted by 40inches
I have one fitted, simple but effective.
Prop Catcher
I like that one, Afraid I'm going have to plagiarize that I hope you don't mind.
That will be 2 of us then 
.Can't remember where I saw it originally, one at the front would be nice, but a bit difficult on a bike engine
Edited to add that I say them first here: http://www.locostbuilders.co.uk/viewthread.php?tid=155223&page=1
but wanted to panel the tunnel in and couldn't wait, so I made my own. I think FASTdan was selling them for £20 for 2 sets
[Edited on 23-1-12 by 40inches]
40inches - 23/1/12 at 02:53 PM
quote:
Originally posted by loggyboy
quote:
Originally posted by 40inches
simple but effective.
Has it been tested then? or are you just hoping so?
(not saying that it isnt/wont be - just wondered!)
Don't see why it would not work, not keen to find out though
It would be plenty strong enough, 8mm cap heads through the chassis member with nyloc flange nuts.
Wouldn't use rivnuts though, although they may hold it long enough before breaking free.
loggyboy - 23/1/12 at 03:17 PM
quote:
Originally posted by 40inches
Don't see why it would not work, not keen to find out though
It would be plenty strong enough, 8mm cap heads through the chassis member with nyloc flange nuts.
Wouldn't use rivnuts though, although they may hold it long enough before breaking free.
Im not to concerned as the forces on the rivnuts and assoc bolts would be lessened by the fact the plates are bent over, so the shape of the catcher
itself would be taking any force from a loose prop. The bolts are really their to just stop the catcher from falling over.
big-vee-twin - 23/1/12 at 04:36 PM
Think fast dan sells them for a reasonable cost, not worth messing about - just get one from him.
loggyboy - 23/1/12 at 04:40 PM
quote:
Originally posted by big-vee-twin
Think fast dan sells them for a reasonable cost, not worth messing about - just get one from him.
His are mounted to vertical members, which is fine if you just want one central one, as in the strikers case the vertical members are not located in
the positions I wanted the catchers in!
mcerd1 - 24/1/12 at 08:15 PM
quote:
Originally posted by loggyboy
quote:
Originally posted by big-vee-twin
Think fast dan sells them for a reasonable cost, not worth messing about - just get one from him.
His are mounted to vertical members, which is fine if you just want one central one, as in the strikers case the vertical members are not located in
the positions I wanted the catchers in!
same problem with my dax - but I've got even less tubes to attach too 
svante - 25/1/12 at 01:27 PM
I didnt have one....
But the propshaft didnt separate, it just got a little off center.
It was all caused by a broken weld in the gear extension.
I broke the gearbox in half
loggyboy - 15/6/13 at 08:07 PM
just thought id add the pics of them both finished and powder coated to this thread.
Dusty - 15/6/13 at 11:58 PM
I think the design and materials are OK but would put more thought into the positioning. Props do go at the joints and yours would be restrained in
that case. The prop tube can also fail, more toward the centre and if your prop fails six inches in front of the rear UJ you would have a lot of prop
thrashing about. I would move both a little more toward the centre of the prop or am I being a bit anal?
loggyboy - 16/6/13 at 12:10 AM
quote:
Originally posted by Dusty
I think the design and materials are OK but would put more thought into the positioning. Props do go at the joints and yours would be restrained in
that case. The prop tube can also fail, more toward the centre and if your prop fails six inches in front of the rear UJ you would have a lot of prop
thrashing about. I would move both a little more toward the centre of the prop or am I being a bit anal?
If I was running a massive torquey v8 or turbo I would agree, but chances of the acctual prop shaft failing from 150ft/lbs is slim.
