Practically Classics Forum

I am bored of welding (plus the feed on my welder has broken (parts on order)) so I'm doing "little" projects this week. One of these is to fit a gas lift to the bonnet of my RRC.
You can buy gas struts in various lengths and throws, I am fairly sure I can find out what I need by marking the bolt positions on the outside of the car and measuring between them with the bonnet open and closed. But how do you work out the force required? My bonnet is "spring assisted" which makes it lighter but it is still fairly heavy. I don't want to go too low pressure and have it still needing assistance likewise I don't want to go to high pressure and have it ping back and jolt the hinges.

This page puts it so much more succinctly than I would from memory (and old notes from my student days. )

Enjoy.

TerryG wrote:I am bored of welding

What are you welding,a rotter?

I spend 3 hours looking for how to calculate this last night and the closest I got was using a luggage scale to lift the bonnet from the position of the hinge mounting bolts, you spend 5 minutes and come up with the formula.
I'm sure Google on my laptop is broken

Terry, instead of asking with words, I asked Google images with a picture of a tailgate strut and that page was connected to the thirtieth image on the first page of hits, some of which involved asps - the sort used by Police Officers to hurt the bad guys - as they look quite similar in a poor light.

I'm sure the luggage scale way of working it through would have had more potential for entertainment!

Terry,
There's a firm on line making and selling gas struts for various vehicles. They are SGS engineering. They may be able to help you and save a lot of head scratching! I tried ringing them a couple of weeks ago, I need hatchback struts for my Maxi,only there was a problem with their telephones. Probably resolved by now as I have been too busy to chase them up. And a block of wood holds the hatch open quite well

I thought the wood came as standard with any Maxi beyond a few months of age! The outfit in the link I posted this morning are alive & well and taking orders, so - Young Farmer - if yours are still in hiding by the weekend, give them a shout. Someone at the place will probably have the Maxi rate and size tattooed on the inside of his eyelids as they're so often needed.
The Corolla's "Liftback" (Oh please, it's a boot lid FGS!) struts are original and after 25 years are still capable of bruising the chin quite annoyingly if I pull the lever to open the luggage region and park myself too near the car as the back comes up.

Cheers gents, I have sent a couple of companies emails as I can't be the only person in history that has wanted to do this.
Hopefully the other half will pop to see her mum tomorrow evening so I can borrow the bathroom scales and weigh my spare bonnet.
To see what the difference is between doing it properly and guesstimating, I took the opportunity to use the kitchen scales earlier. At the leading edge of the bonnet I need 5.8-6.4kg to lift it. As I would quite like it to stay open if there is a bit of a breeze say 7. The bonnet is 97cm long but the pivot is 13cm behind the trailing edge. The only place I can mount the bonnet end of the struts is 5cm from the back of the bonnet and in line with the pivot so assuming I remember correctly how a lever works, I need 45kg of lift between 2 struts to open it. I need to work out what the stroke options are based on my existing bolt holes but that can wait until tomorrow as I forgot to measure their locations today.

TerryG wrote: I'm sure Google on my laptop is broken

honest, it wasnt me!!

err whoops apocalypse!

I might have to look into this as the neon's bonnet has an ever increasing hole for the bonnet prop!
Let us know how you get on and I will start with a few needed measurements!