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Prop Catcher
Daddylonglegs - 20/4/11 at 07:23 AM

I'm in the process of fabricating a prop catcher for the Locost. Having looked at several on here, I've decided to go with the style here.

The only thing is, I'm running a live axle so there will be a reasonable amount of up/down movement of the prop. What should I leave as a gap to allow travel?

The last thing I want to do is cause the prop to wear at the catcher and have 2 small prop shafts flailing around in the tunnel

Thanks.

JB

designer - 20/4/11 at 07:45 AM

Usually it is the UJ at the engine end of the prop that fails and the catcher should be within six inches of that.

Keep it simple. Why not just mount a bar across the lower members?

daviep - 20/4/11 at 07:48 AM

You need to jack up the back and let the axle go to full droop and then take off the springs and lift the axle into full bump. I would leave 10mm clearance in droop and 25mm clearance in bump to allow for the bump stop compressing.

Regards
Davie

mcerd1 - 20/4/11 at 07:50 AM

edit - davie beat me too it ^^

if you make them like that there should be no way that it can touch unless the prop breaks



[Edited on 20/4/2011 by mcerd1]

Daddylonglegs - 20/4/11 at 07:54 AM

quote:
Originally posted by designer
Usually it is the UJ at the engine end of the prop that fails and the catcher should be within six inches of that.

Keep it simple. Why not just mount a bar across the lower members?


I think the theory is that the closer to the prop you can 'catch it' the less chance it has of building momentum and wreaking havoc! I've seent he result of what these things can do and it's scary

Cheers Davie, I'll be doing just that this evening

Edit: BTW, I've asked D&F if they can supply the bolts for the diff flange, but if they can't, does anyone know where I can get them? The mounting holes seem to be around 7.5mm-so I'm guessing 5/16?)

Also, I am going to thread lock them, but is it better to wirelock?

[Edited on 20/4/11 by Daddylonglegs]

macc man - 20/4/11 at 10:40 AM

I would say that prop catchers are more suited to IRS installations that have very little prop movement. Best just to fit a diagonal bar to the central chassis where your legs are. Unless the prop is restrained to a very small degree I dont think it would do much good.

snapper - 20/4/11 at 10:58 AM

If in doubt then steel plates either side welded to the tunnel bars will stop it coming into the cockpit.
It's a road car and your not a professional racer so the extra weight and safety is worth it IMHO

FASTdan - 20/4/11 at 01:33 PM

I was thinking something along the lines of this (2-off to make a full circle obviously).....

Description
Description

6mm MS plate. The only mode of failure would be buckling, will run a quick FEA to establish the force needed to buckle this but I suspect it would be far greater than the force required to shear the fasteners.

Possible future product depending what price I can do them at?

designer - 20/4/11 at 02:54 PM

quote:

6mm MS plate


That's overkill, aluminium that thickness would do.

FASTdan - 20/4/11 at 03:33 PM

quote:
Originally posted by designer
quote:

6mm MS plate


That's overkill, aluminium that thickness would do.


Yeah I had considered that and I suspect you are right. Its a pretty rigid structure and the FEA indicates its massively overkill.

Weight wise in 6mm MS its 800g per pair of plates, as compared to 300 in alu.