Rear Tyre Carrier

[Jim_Phillips]

I have been giving some thought to the design of a rear tyre carrier.

The last one I made had a couple of problems. Namely, the fixing point to the vehicle was the same as for a tow bar - the chassis. This meant that I couldn't fix a tow bar. The other problem was the weight of the tyre was a long way from the fix point, this put a lot of stress on the hinge. The whole thing was under engineered and has since been discarded.

My latest idea (no jokes about British Engineering please) is to mount the tyre on one end of a hydraulic ram... The tyre will slide away to allow access to the drop down door rather that swing away. I plan to mount the ram onto the pintle hook point. The Tyre will be fixed to the end of the ram - hey presto! In my mind's eye it all looks quite neat.

Before I start searching the scrap yards for an old hydraulic ram, can anyone see a pitfall with this plan? BTW, I don't intend to use hydraulic pressure to move the tyre - that would be too clever ...

Cheers, Jim

 

[landtank]

I don't quite understand what you have planned but I can't imagine a weaker point of attachment than that pintle point. Slee sells the hardware to build your own swing away carrier. I have a 35" on mine with no problems. I do however have a Kaymar and am not clever enough to make my own,

Rick

 

[Jim_Phillips]

This is to give a rough idea of what I have in mind...

 

[woody]

sorry, this has to be said....hehehehe

The used/old hydraulic ram sounds like the perfect British idea, should leak just enough oil...

(yes, I have a MGB that drips too...lol)

The drop down mount will suck if you need access to the rear and have to climb over it every time.

 

[Jim_Phillips]

Woody - That's a cheap shot There will be no oil in the thing - no leaks! I'll be the one that's laughing when you're begging me for the US distribution rights...

Cheers, Jim

 

[Jim_Phillips]

>>>The drop down mount will suck if you need access to the rear and have to climb over it every time.

Why would I need to climb over the ram? I'm looking for a ram off a fork lift truck - those things are only a few inches in diameter.

You'll see..... Jim

 

[Beowulf]

Jim,
As I understand the project, the tyre will move horizontally when you want access to the tailgate, correct?

If so, then:
1. How do you compress & extend the hydraulics?
2. Does the tyre move toward curbside or streetside?
3. How to you control torsional movement. i.e. does the tyre lock in the open and/or closed positions with a pin?  

I think you're on to something here. I like this idea much better than mounting the tyre on the bonnet.  :G

After almost 2 years with mine under the truck and now a couple of months with it on a swing-away arm, I'm beginning to see why you would want another arrangement.  Case in point; we were helping some friends move this weekend. I loaded the back of the Wonder Truck with boxes. Another helper parked their car directly behind mine, not leaving enough room for the tyre carrier to open so I could open the hatch, unload, and get on my way. No big deal, just a little "gotcha" with the swing out arms.

Keep us posted!
-B-

 

[Jim_Phillips]

-B-

The tyre can move either to the street side or kerb side. I plan to have it move out to kerb side. I'll need to do a little experimentation with the hydraulics. It may work with no oil in it - then again it may benefit from having a little friction. In which case I will connect the 'oil in' to the 'oil out' That way the oil will just move from one side to the other - ie. removing, replacing an equal amount.
The locking mechanism is demonstrated in the pic. The red bar slides inside a sleave of a slightly larger diameter. It is secured with a pin when closed. This bar also prevents the trye from falling away from the vehicle and gives it extra stability as well as taking some of the load off the ram oil seal.

Cheers, Jim

 

[Keep]

I agree with -B-, it takes too much room to open the rear doors now that I have a swing out. Jim could be on to something here.

 

[landtank]

Wouldn't a heavy duty draw slide work better? This way it would stay straight up and have better mounting. The slides I'm thinking of have three pieces and extend to twice there closed length. Something about 4" wide would be enough and usually these can slide apart completely with just a lever action so the tyre and mount could easily be removed leaving just the base on the bumper.

 

[Jim_Phillips]

Rick

I thought about that too - how would you keep the sliding mechanics from getting clogged up with dirt and grit?

c

 

[Beast II]

I think that is a brilliant idea. What do you think it'll cost to build ?

 

[Gumby]

I'm liking it too. I had a swing away for about two years. All the problems I had for road use i wrote off because it was "good for wheeling, screw the rest" Turns out after I wheeled it a couple of times, I didn't like it back there either. Now I use the cell in town and I'll put the spare in the back on the trail. Getting it out of the back is really not much less of a pain than getting it off the carrier was. I really am enjoying my easy access to the hatch again. Way too many times I would just use the back doors rather than wrestle with the latches and swinging the tire out.
Hydraulic might be a bit too complicated though. I like the idea of a heavy duty slider. Might be easier to tuck in a bobbed bumper too.

hmmmmm... Time to fire up the solid modeling software.

 

[Jim_Phillips]

It was the draw sliding mechanism on an old metal filing cabinet which first triggered the idea. I'll visit the scrap yard tomorrow and see what I can dig out. I still like hydraulics simply because it's a sealed unit. Nothing to seize up and a clean look. We'll see. Let me have any ideas..

Cheers, Jim

 

[woody]

aahhh...yer second sketch cleared everything for me....but I'm still waiting for leaks...

problem I see is, hydraulic cylinders are round, and you'd need to control the rotation of the tire mounting somehow, both in the stored position and while extended....However, it does look like a neat idea!

We have farm-type cylinders locally for $50, 8" stroke.

IMO, you might find more rigidity with a "drawer-glide" type arrangement...seems to work well for rollercoasters and monorails and such, and might better lend itself to opening BOTH directions.

 

[semlin]

It sounds neat, but wouldn't the weight of the tire bouncing up and down laterally on one end of the ram destroy or bend the ram shaft pretty quickly?

What about putting the ram onto some kind of pivot so that the ram pointed up 12 o'clock when underway then swung down to 3 o'clock (or 9) horizontal like a clockhand when stopped and then you slid the tire out of the way. It would require an L shaped mounting bracket as illustrated below (for a clockwise rotation) with "t" being the top of the ram and centre of the tire mount, "p" being the bottom of the ram and the pivot point and "o" being a removable pin on the end of the bracket that you would pull out to release the mount to rotate and then replace as a rest for the ram. You could also put a diagonal cross brace between "T" and "O" for added strength.

T
[]
[]
p=====o


my 2 cents anyway

 

[Photoman]

Jim,
I have a good bit of experience with hydraulic cylinders. I will speak in generalizations as there are many different kinds but the same basic idea. As Semlin pointed out they are not designed for lateral loads. On the back of the rod (the part inside the cylinder) is just packing like leather washers. They are tapered on the outside edges. For a double acting cylinder like on forklifts half the tapered packing is facing one way and the other half the other way. The leather like packings extend beyond the metal part of the packing about 1/8" or so and are held on to the rod with a single bolt in the end (center) of the rod. It is hard to slide the rod in and out. When I rebuild them I remove the front of the cylinder and use the hydraulics on the machine to blow out the rod. The front of the cylinder that unscrews has a seal on the outside, one or more wipers to remove dirt, and a plastic/teflon insert to guide and support the rod. Woody made a very good point about controlling the rotation of the rod. Another way to make your idea work is to use air. You can run a hydraulic cylinder with air. The feed would have to be reasonably slow to keep from shooting that puppy out but it would work. $.02 worth.
Bill

 

[landtank]

For stability and strength you could use two pistons. They could be of smaller diameter since they are sharing the load.

 

[Jim_Phillips]

I'll keep everyone posted on this. Thanks to all for input and ideas.

The only way to find out if the design works is to build it and test it. I'm going to see Fred Watson Scrap Merchant ( AKA Scrappy Watson) and have a poke around his impressive junk yard.

If I see a drawer type mechanism I might be tempted to switch design plans but I intend to go for hydraulics. Anyone that remembers my Hub socket from SOR days will no doubt testify that I don't tend to under engineer .....



Cheers, Jim

 

[cruiserdan]

Jim,

You will paint it this time, won't you? 8)