P38 winch bumper build

[elbekko]

I've been thinking about getting a winch bumper for my P38 for a while. Nothing out there really speaks to me. Either it's ugly or ludicrously expensive.
I want something that follows the stock bumper and body lines as closely as possible, and is sturdy but doesn't weigh more than the moon.

I bought this winch a while back: VEVOR 13.5k winch
It appears to be surprisingly decent quality. I've had the gearbox open to clock the freespool lever, and everything inside looks good. Decent grease in there too, although I'll probably replace that anyway.
The only thing I might change (eventually) is the solenoid, as it's a bit too chinese to my liking.
Overall, it seemed very much worth it for the price.

So, onto the design. I've been battling Fusion 360, but I think I'm starting to get sort of used to it.

The top, bottom and chassis plates are 5mm, the front plate is 3mm. The idea is to use S355 for some extra strength.
Integrated skidplate/radiator protector which bolts to the front chassis crossmember.
Winch goes feet forward, pulling force should be pretty well in line with the bolts through the chassis.
Some stiffening ribs can probably be added in the side wings here and there.
Fusion estimates the bumper is around 42kg like this, which I think is fairly in line with bumpers like this? Maybe a little more than I would've liked. But doesn't seem any worse than the FirstFour bumper I had on my RRC, that had its own gravitational field.

The winch is modelled very roughly, but should be close enough for the purpose.

My main points I'd like feedback on:

* Will the 3mm front plate be enough to take the forces from the winch? Or should I maybe more go for a "cradle" of 5mm plate that is a U bent up between the chassis rails, and then skin the remainder in 3mm?
* How hard will it be to bend 3mm plate around that curve? My idea is to weld and hammer, but not sure how well that'll work, especially with S355?
* How do I get Fusion to give me a flat pattern for the whole front plate, including the curves? It refuses to see it as a bend, so won't put it into a DXF correctly. Worst case I need to remodel it somewhere to get it cut out.
* Not sure how/where to add recovery points yet. In between the chassis plates would probably be best, but can't really decide what I want. My first thought was to extend the chassis plate through the bumper as an eye, but that's then only 5mm plate, and won't be easy to make and make look good.

Feedback and thoughts very welcome

A dump of pictures. The blue component is the body line. The little cylinder coming out at an angle is the freespool lever (clockable per 30ish degrees).

 

[miketomcat]

I built a bumper for my discovery years ago. I built the whole thing out of 5mm plate

The winch was feet down, however I forgot to add an up stand across the back of the tray. Consequently it bent and broke the winch casting so I added a bit of 5mm angle across the back.

The second bumper was on the tomcat. This one was a 6mm bought winch tray (an unequal C section) this I added sides and chassis mounts, this never moved.

Personally I don't think 3mm is enough for the winch mount unless beefed up. Other than that I like it.

Mike

[elbekko]

2 hours ago, miketomcat said:

Personally I don't think 3mm is enough for the winch mount unless beefed up.

Even with feet forward? It should minimise the twisting forces you get with feet down, and is stiffened up by the 5mm plates top and bottom.
But yes, it's a concern. Hence why I'm thinking of making the winch cradle a single, bent piece of 5mm, and then 3mm for the wings.

Thinking, maybe it would be better to have the top and bottom plates 3mm, and the front plate 5mm? Would probably reduce the weight a bit as well.
Or everything 3mm except for the winch U cradle at 5mm. Then I don't have to try and bend 5mm plate for the curved corners.

Edited May 16, 2023 by elbekko

[miketomcat]

I would go 5mm for the winch cradle and 3mm for the wings. You want the wings to protect the body but not at the expense of bending the chassis. You could go 3mm all over and add stiffening/bracing where required but assessing where to best put the bracing may be tricky.

Mike

[elbekko]

I'll see if I can knock out a design for that tonight, shouldn't be too difficult.

Any feedback on recovery points? I see on your pictures you had small rings, was that good or would you have preferred something else?

[miketomcat]

The disco were part of the leg that bolted to the chassis doubled up in thickness. Worked well with shackles.

The tomcat were M16 lifting eyes bolt through the front face with a 3" square doubler on the back.

The ibex has a bit or 10mm angle braced and doubled bolted to a deadicated point on the chassis.

Mike

[landroversforever]

First thoughts on weight.... that sounds heavy for what is a pretty 'small' bumper. My Defender ARB is 44.2Kg and my First Four Tubular one 21Kg. 

I'd agree with Mike that the 3mm probably isn't stiff enough for a winch of that style, the rely too much on the mounting staying rigid and flat or they jam up. That said, 3mm if you can make it stiff enough might be work OK. 

Boxing in the back of it, or even just lips, will massively stiffen up the wings.

For the flattening of those curved pieces for cutting.... how have you drawn them? In Catia I'd do that as a surface and use the sheet metal workbench to recognise that and then make it up to the metal thickness. Does that make sense? They need to be recognised as sheet metal components to be able to be spat out. 

Worth adding that my laser guy likes stuff as step files for cutting as it recognises bends etc in the software and is tailored to their tooling radii. It will add/remove the relevant material. Example of which was a part for work which had been designed with some stupid ~25mm radii that was purely aesthetic... his software was able to sort out bringing it down to the ~4mm rad they used for it in the end. Something like the curved panels can also be done with many smaller bends, small enough that a small DA sand after it looks curved rather than bent. 

[elbekko]

Made another iteration, with the cradle as one piece of 5mm, and outer chassis plates 5mm as well. The rest is 3mm.
This brought the estimated weight down to 33kg, and 3kg for the skid plate (also from 3mm).

That seems a little bit more reasonable. And should be sturdier too.

13 minutes ago, landroversforever said:

Boxing in the back of it, or even just lips, will massively stiffen up the wings.

Boxing in the lips is a good idea, not sure how easy that'll be to do. One side has the windshield washer reservoir there...

19 minutes ago, landroversforever said:

3mm probably isn't stiff enough for a winch of that style, the rely too much on the mounting staying rigid and flat or they jam up.

That's a good point, and a good reason for the 5mm cradle. It'll also be welded along the side plates to the top and bottom plate, which should stiffen things up substantially.

I've also been playing with the idea of supporting the winch on the bottom and top plate using some tabs that go to the tie bars. That would remove even more twist from the system, I think.

13 minutes ago, landroversforever said:

For the flattening of those curved pieces for cutting.... how have you drawn them? In Catia I'd do that as a surface and use the sheet metal workbench to recognise that and then make it up to the metal thickness. Does that make sense? They need to be recognised as sheet metal components to be able to be spat out. 

I managed to find it in Fusion now - a lofted flange. In the previous iteration I modelled it as a solid and converted to sheet metal, but it didn't want to make a flat pattern from that.
Now it does want to, which is good.

15 minutes ago, landroversforever said:

First thoughts on weight.... that sounds heavy for what is a pretty 'small' bumper. My Defender ARB is 44.2Kg and my First Four Tubular one 21Kg. 

I would think this is probably fairly similar in size and design to the ARB (but without the wings). Tubular ones are usually lighter, yes, but also fugly on a P38...

For the record, with some dimensions:

[landroversforever]

Other thought with the winch cradle and a way to take some weight out... Is there a reason you're going feet forward with the winch? If you go feet down the front and top panels don't need to be anywhere near as strong, and you can then add ribs to keep the mounting face flat. 

[elbekko]

1 minute ago, landroversforever said:

Is there a reason you're going feet forward with the winch?

In my mind that seems the stronger direction for all the forces involved. Feet down you're trying to twist the bottom plate into a pretzel between the chassis legs.
But I'm no engineer

[landroversforever]

Just now, elbekko said:

In my mind that seems the stronger direction for all the forces involved. Feet down you're trying to twist the bottom plate into a pretzel between the chassis legs.
But I'm no engineer

You are to a certain extent, but it does mean you can keep the plate stiff far more easily IMO. 

[landroversforever]

If it's any help, one of my plans if I use the ARB on the build is to convert it into a feet down mounting for the winch so I can still use my fancy fairleads. I'm not worried about making that strong enough. with ribs etc to make it behave like a much thicker piece of material. 

[miketomcat]

I think V2 should work out fine. I can't see in the picture but does the winch mount have a return on top and bottom edges? Mine had a return at the front (the fairlead was bolted through it) but the back (by the radiator) didn't this is where it bent, once I welded a small (about 1") return on it never moved again.

Mike

[elbekko]

31 minutes ago, miketomcat said:

I think V2 should work out fine. I can't see in the picture but does the winch mount have a return on top and bottom edges? Mine had a return at the front (the fairlead was bolted through it) but the back (by the radiator) didn't this is where it bent, once I welded a small (about 1") return on it never moved again.

Mike

That's a good idea, I could pop a piece of angle over the back.

 

9 hours ago, landroversforever said:

If it's any help, one of my plans if I use the ARB on the build is to convert it into a feet down mounting for the winch so I can still use my fancy fairleads. I'm not worried about making that strong enough. with ribs etc to make it behave like a much thicker piece of material. 

I was under the impression that feet-forward would be easier to make stronger, lightly. Hence why that was my original design decision. Feet down could definitely work, but would make accessing the freespool a little bit harder, as it's popping up in a perfect spot right now.

[Bowie69]

Can you not rotate the gearbox and therefore move the freespool?

Honestly I think it's easier to get an up/downstand on a feet-down mounted winch, but I'm not sure about the P38 limitations.

[elbekko]

1 hour ago, Bowie69 said:

Can you not rotate the gearbox and therefore move the freespool?

That's what I did to get it in a good position for feet-forward. But not sure how well that'd work feet-down. The standard position it with the freespool straight up, and then it'd go straight into the body/grille. All solvable, but this way it actually comes out quite neatly just in front of the body line.

[miketomcat]

I don't think there's any problem with feet forward especially if that lower guard is removable giving good access to the winch.

Mike

[Daan]

I think 3 mm could work, granted a flat 3 mm plate does not do much for you, but once you give it decent returns top and bottom, you have a channel that is plenty strong. My rear winch mount is just a folded channel of 3mm with the winch bolted on top of this, feet down. Lots of holes drilled into it, around 8 kg. 

All you need to do is to have an as direct line of force from the winch mounting points to the chassis. The rest is just hanging around it for show.

The bash plate, I would remove the slots, and just have some holes at the bottom for drainage. What has worked for me is to have a bit of box section on top of the bottom edge with a stay going upwards to the chassis to stop it bending in the middle. 

Daan

[elbekko]

1 hour ago, Daan said:

I think 3 mm could work, granted a flat 3 mm plate does not do much for you, but once you give it decent returns top and bottom, you have a channel that is plenty strong. My rear winch mount is just a folded channel of 3mm with the winch bolted on top of this, feet down. Lots of holes drilled into it, around 8 kg. 

All you need to do is to have an as direct line of force from the winch mounting points to the chassis. The rest is just hanging around it for show.

Thanks for confirming my initial thinking. And I think with this design that line of force is about as direct as it can get.
The 5mm cradle is probably a good tradeoff in strength vs weight, and allows me to make the rest of the bumper out of thinner material.

Speed holes aren't the worst idea, might be worth putting some in the bottom plate to reduce weight. And would help with drainage.

1 hour ago, Daan said:

The bash plate, I would remove the slots, and just have some holes at the bottom for drainage. What has worked for me is to have a bit of box section on top of the bottom edge with a stay going upwards to the chassis to stop it bending in the middle. 

Part of the radiator is behind there, and without the slots too much airflow would be blocked. The stock bumper has slots there as well, for that reason.

[elbekko]

1 hour ago, miketomcat said:

I don't think there's any problem with feet forward especially if that lower guard is removable giving good access to the winch.

Mike

Realistically the bumper will have to come off to get to the winch. But that's no huge issue, I think

[steve200TDi]

For recovery points you could ad some round bar and bend it in a loop, then welded it to the 5mm plate down each side for maximum strength. his is what I did on my winch bumper.

I've annotated your drawing here:

I also used 6mm steel for the winch tray part between the chassis and folded up the edges as seen here:

Steve

[elbekko]

2 hours ago, steve200TDi said:

For recovery points you could ad some round bar and bend it in a loop, then welded it to the 5mm plate down each side for maximum strength. his is what I did on my winch bumper.

I've annotated your drawing here:

That looks pretty good. And smart to add it to the outside plates, so a double-line pull would load both plates.
Also in line with my first thought of extending those plates out through the front plate to form a ring, but I think round bar will work and look better.

[landroversforever]

9 minutes ago, elbekko said:

That looks pretty good. And smart to add it to the outside plates, so a double-line pull would load both plates.
Also in line with my first thought of extending those plates out through the front plate to form a ring, but I think round bar will work and look better.

If you put those kinds of bent bar style ones on and put them in line with the chassis rails and angled correctly, you'll be able to weld them one leg to each plate. That's obviously dependent on how far into the bumper the chassis legs extend.

[Bowie69]

Also, bent bar means soft shackles don't get ruined on the edges of flat plate with holes in it.

[elbekko]

2 hours ago, landroversforever said:

That's obviously dependent on how far into the bumper the chassis legs extend.

You can see that here:

On 5/15/2023 at 10:30 PM, elbekko said: