1970 lowboy brake conversion

[Jizzo17]

Hello everyone, 

I have purchased a new to me equipment trailer which only has service brakes on the rear axle. It came with two axles from another trailer with ~100k miles on them. They have the service and park break chambers. I would like to add the r12 and r14 valves to the trailer and plumb them up correctly with the anti compounding valve. 
The trailer has two air tanks along the frame rails. One is fed from the service side and the other is fed from the supply side. But they both feed into sides of the only r12(?) valve. Which may be normal for that old of a trailer but it has me puzzled on how I can connect it all together.

So if anyone has a tank off a trailer that has those valves already mounted I would be interested in purchasing it. Or someplace that might have one. That way I can just bypass the old tanks and lines to just run new ones. 

[mrsmackpaul]

I would think any business that sells trailer and truck parts would have a good selection of tanks on the shelf 

Most low loader trailers dont have enough room for tanks in the area around the axles and the like

 

They always look like they have bucket loads of room but when on full oscillation the axles cans tend to move a lot more than people think 

 

Paul

[Geoff Weeks]

Heavy equipment trailers were exempt from the spring brake requirement and may be still are.  You need to plumb it correctly with an SR-5 valve not just with a relay valve.

Look at Bendix's air brake manual for the correct plumbing or leave as is a carry some chalk blocks. 

Edited 5 hours ago by Geoff Weeks

[Jizzo17]

Thanks for the help. I have a few places I could call around to for what I’d need. They are just an hour or so away from me.

 

I think I could swap the 30/30 cans to just single 30s. But im not sure which would be easier/more cost effective to do. It may be one of those six in one hand, half a dozen in the other scenarios. 

Edited 6 hours ago by Jizzo17

[Geoff Weeks]

Coupla things, screw clamps on rubber air lines are not permitted. No way "one is fed from service the other from supply". You've got to get what you have legal before trying to add spring brakes. Without seeing the whole air system, I can't tell what is buggered up and what if anything is correct.

What I can see from that one picture will get you shut down in a heartbeat. You've got kinked copper line. 

I would correct the  defects that will get you shut down. I towed many trailers without spring brakes (I was a heavy hauler) over the years. Once the system is correct, you can see if there is enough room to add what is needed for spring brakes.

Also need to correct what is wrong with the RH S cam bracket, the push rod is not inline with the slack adjuster. It looks like something with the slack adjuster bushing isn't right, preventing the can as push rod from being properly in line.

everytime I look I see more wrong, right chamber fully extended, left chamber fully retracted, what the heck is going on there? Stuck or air to one chamber only? 

Edited 5 hours ago by Geoff Weeks
updates

[Jizzo17]

I really don’t know what the previous owner had going on with the brakes. I’m going to cut those axles out and weld new ones in. And will also put new air lines in. This is really just a trailer to haul my trackhoe and dozer between farms. But I want to make it as safe as possible. 
 

I just thought it may be easier to buy one of those tanks with the valves attached and mound it inside the frame. 
I’ve added a pic of what I’m referring to. 

[Geoff Weeks]

1st, it looks like they are 12" brakes so new axles will also need to be "low boy" axles, 2nd that is a lot of brackety to weld in for no gain.

What is wrong with the current axle?  

Axle and brake are two different things. 

That may be an SR-5 but I can't tell from the picture.

What size tires does it have on it now?

[Jizzo17]

I don’t think there is inherently anything wrong with the current axles. But I also haven’t tried pulling it with it loaded. All 8 tires are no good is the issue. 
 

I don’t know the tire sizes off the top of my head but they are the same height off the ground to the top of the tire. The newer axles and tires came off an oilfield trailer. I have enough space between the brake hardware to mount the center bracket for the walking beam suspension. Someone before me has already replaced one of the axles. As it’s not the same as the other you’ll be able to see in the picture. 

 

Edited 2 hours ago by Jizzo17

[Geoff Weeks]

Those look like 20" rubber not the 15 that most lowboy's from that era had. 9.00x 20, You can mount tubeless demountables on there 295-75-22.5 would be the same OD or you could go smaller 255's which would lower the deck height a bit.

I think I'd start by assessing what is there, and how well it is done.

If the axles are installed in alignment with the king pin, I wouldn't change. If it was scabbed in and everything is out of alignment, then you are going to have to cut it out to align anyway. Alignment is done by how the brackets are welded on. Everything will be "floppy" until welded, and you better get it right.

One looks to be "Propar" axle and one looks to be a axle where the spindle is smaller for the outer bearing.

One thing I see in the latest picture that concerns me: Will the tires clear when the suspension is tilted to either extreme?

It looks like they will hit when the rear is compressed fully and the front might hit when it is compressed fully.

Better to find that out now, rather then after you do all the work. It wouldn't surprise me to learn it had 15" hubs on it from the get go, and someone changed without checking clearances.

New axles with 12" brakes and 17.5 tires would be the modern equivalent. I did one axle job on a trailer, measure 4-5 times and weld once! 

 

[Jizzo17]

Yea the plan was to swap the 22.5 or 24.5 rims that are on the replacement axles to some 17.5 low pros if I ended up having clearance issues. 

[Geoff Weeks]

Check the clearance 1st. The tires you have on there now are equal to lo-pro 22.5 in diameter, if it hits now, then really the only choice is 17.5 which take a different brake set-up (12.25 x 8 drum) S cam and bracket. Most cases you can't just swap hub and brake spider, as the spider is welded on.

Going off road, you know those axles are going to have to pivot to the extreme going over rough ground. Better to know now rather than do the work and get stuck or tear up tires.

I've not see a early low boy like that with anything other than 15" hubs (which will take 17.5 tubeless "adapters") 

Set up with new axle and hub pilot 17.5's would make that a good trailer if the rest isn't all cracked and scab welded.

 

[Jizzo17]

I realized that I wouldn’t be able to swap to 17.5 after i got off here and started thinking about it more. 
 

i shouldn’t have a problem with clearance with the 22.5 because i drug that trailer across a couple ditches and the wheels were spinning freely. 

[Geoff Weeks]

255 70 22.5 is the smallest you'll be able to fit to what you have there now, Will be smaller than the 9.00x 20s'.

I'd still check before I assume. Loaded will make a difference.