Macman Posted July 11 Share Posted July 11 I have been told there is a way to upgrade to spring breaks on an LTL by using parts from an R model. Does anyone know how this goes? Quote Link to comment Share on other sites More sharing options...
67RModel Posted July 11 Share Posted July 11 If the original setup is anything like the rotochamber arrangement on a B81 / Early DM800 good luck. When I had my B81 I tried everything possible off the shelf to upgrade the brake chambers but nothing was suitable. The only path forward was a lot of custom fabrication or potentially buying all the parts off of a later model DM800, but even this would probably require fabrication to mount the S cam shafts to the axle housings. Bottom line is the brakes on those models were just not set up for modern 30/30 or even 24/24 chambers. There just isn't enough room. Any small amount of suspension articulation would crush the brake chamber between the axle housing and the frame rails. I have since sold the B81 so its not my worry anymore but I could never come up with anything straight forward that would work. Do you have any pictures of the LTL brake setup? I'm not familiar. 1 Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted July 11 Share Posted July 11 On my B model i tried puting a 24/24 chamber on but its very tight to the rim. I'd assume you would have the same issue. To get 30/30 chambers you Probably need spiders and S cams off a R model to get the cans away from the rims. Possibly re clock them so the cans don't hit the frame rail. That being said I have never tried to swap b and R spyders so not sure it will inter change? Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 11 Share Posted July 11 This has been around a few times (maybe a lot more) on here So from memory Off set slack adjusters, there is such a thing And a plate the bolts onto the old bracket that offsets the can maybe a inch - inch a half Abd of course the plumbing Doing this means a 30/30 can bolts on and it is a really straight forward conversion Paul Quote Link to comment Share on other sites More sharing options...
Macman Posted July 12 Author Share Posted July 12 Wow thank you all for your help. I will try to find some of these parts. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted July 12 Share Posted July 12 6 minutes ago, Macman said: Wow thank you all for your help. I will try to find some of these parts. My memory is fuzzy but I know the axle tubes from b models to R models are definitely different. For example a r model differential will not drop in a b model era housing. The spiders may swap over. Another thing to consider if your truck currently has camelback is just swaping in R model axles. It might be the same labor but you could get some 4:17 ratio and have a great highway speed now. Just a thought Quote Link to comment Share on other sites More sharing options...
67RModel Posted July 12 Share Posted July 12 (edited) In my experience with the B81 you needed to get the cans way inboard of the frame rails close to the pig. You would need really long S cams. Offset slack adjusters ain't gonna get it gone. B81 stuff is massive though and takes up a lot of space. Then comes the part where the axle housings do not have provisions for S cam and can mounting anywhere. You would need to fabricate something to the axle housing to be able to mount all this stuff. There are a ton of "ifs" and unknowns involved. Mostly trial and error and that is hard to do considering how expensive all the components can get. I honestly at one point thought about getting a pull type maxibrake can and mounting it ahead of the rotochamber and connecting it to the slack adjuster with a chain. That was honestly the easiest way possible to get emergency brakes on that setup. I'm kind of glad that truck is gone. It was too impractical even for a hobby truck. 12.00-24 rubber, 9.10 gearing, quad box, 40 mph top speed, and that archaic brake set up made it not really practical to drive. Edited July 12 by 67RModel Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 12 Share Posted July 12 I think a lot is gunna depend on what backend is in the truck I just assumed it was a Mack 44 as they are the most common out here Once you go to 58's and bigger the room to mount things gets pretty tight Paul Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted July 13 Share Posted July 13 in 60's-70's there was a "conversion " set up which had the spring parking brake can mounted inside the frame rail. camshaft housing bolted to rail with hole in frame for camshaft going to outside rail . early set ups had a long 1/2 dia steel rod connecting slack adjuster on axle to cam going through frame. setting parking brake moved the rod which pulled on axle mounted slack. bad idea! rod too long kept braking. change over repair was putting HD cable on replacing 1/2 dia rod. this set up was used on DM's as well with other models.. Quote Link to comment Share on other sites More sharing options...
Macman Posted July 14 Author Share Posted July 14 On 7/12/2024 at 7:04 PM, mechohaulic said: in 60's-70's there was a "conversion " set up which had the spring parking brake can mounted inside the frame rail. camshaft housing bolted to rail with hole in frame for camshaft going to outside rail . early set ups had a long 1/2 dia steel rod connecting slack adjuster on axle to cam going through frame. setting parking brake moved the rod which pulled on axle mounted slack. bad idea! rod too long kept braking. change over repair was putting HD cable on replacing 1/2 dia rod. this set up was used on DM's as well with other models.. This truck has a hand operated parking brake lever with a cable running back to the linkage on the front axle. 1 Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted July 14 Share Posted July 14 with changing times/ rules and regs ; hand brakes didn't make the grade . parking brakes systems needed to be a higher capability for holding. in comes the mechanical spring brake. another earlier failure was the brake systems using same service can with dual function valve . flip dash switch , valve sent air to cans (same as if someone sitting in seat holding down on treadle valve. great till truck ran out of air ;releasing brakes. 1 Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 14 Share Posted July 14 15 hours ago, mechohaulic said: with changing times/ rules and regs ; hand brakes didn't make the grade . parking brakes systems needed to be a higher capability for holding. in comes the mechanical spring brake. another earlier failure was the brake systems using same service can with dual function valve . flip dash switch , valve sent air to cans (same as if someone sitting in seat holding down on treadle valve. great till truck ran out of air ;releasing brakes. Never saw a parking brake like you describe using air to apply, as its weak point is obvious. Early air braked vehicles (every one I've seen) had drum or disk driveshaft brakes for parking/E brake or had the weird system B models sometimes used with the remote "cans". I did see one hydraulic "hydrovac" system modified with a toggle to open the "back" chamber to atmosphere to apply the service brakes as an additional brake for winching. I'm sure it wasn't factory and was done at a shop, the lines were too small and the length of them would slow the boost application. Tru-Stop disk driveshaft brakes were the only one of it's kind that could meet the required stopping distance, but lacked the self applying component of spring brakes. They could be single or dual caliper depending on what was needed. My Dart had the dual caliper originally but was long gone by the time I got it, brackets and cross bars were still on the truck. It is early 50's. The requirement for self application on loss of air pressure is what killed "hand brakes" on trucks. They did continue on some buses, however. Quote Link to comment Share on other sites More sharing options...
h67st Posted July 15 Share Posted July 15 If you're just going to bobtail or run light, you can install 2024 chambers on a lot of these old trucks. My H model has the SWDL56 (IIRC) rear bogie; it used to have rotochambers next to the frame rail: I "clocked" them one bolt hole to get the chambers below the frame rail. The chambers are very close to the rims because I have 10:00-20 tires; if you are running 22.5 or if you have 22" hubs then this won't be an issue. 1 Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted July 15 Share Posted July 15 20 hours ago, Geoff Weeks said: Never saw a parking brake like you describe using air to apply, as its weak point is obvious. Early air braked vehicles (every one I've seen) had drum or disk driveshaft brakes for parking/E brake or had the weird system B models sometimes used with the remote "cans". I did see one hydraulic "hydrovac" system modified with a toggle to open the "back" chamber to atmosphere to apply the service brakes as an additional brake for winching. I'm sure it wasn't factory and was done at a shop, the lines were too small and the length of them would slow the boost application. Tru-Stop disk driveshaft brakes were the only one of it's kind that could meet the required stopping distance, but lacked the self applying component of spring brakes. They could be single or dual caliper depending on what was needed. My Dart had the dual caliper originally but was long gone by the time I got it, brackets and cross bars were still on the truck. It is early 50's. The requirement for self application on loss of air pressure is what killed "hand brakes" on trucks. They did continue on some buses, however. one unit for sure which had the service/parking brake set up was an old martin lowbed a customer had. small 12 (1/4) in brake pads . set buttons and drop trailer; brakes were locked, using air to hold them. system lost air =trailer lost parking brake. it used to be dropped on blocks since there weren't any landing gear. driver in hurry backed under before hooking lines , trailer rolled away, which is why going for a CDL =requirement was to hook lines before truck went under trailer. old rule based on old system. many trailers rolled away if backed under first. I made a set of 3ft long with 4 in pipe with 3 in pipe inside having 3 sets of 2 in holes for pin to raise/ lower legs. and yes they bent those backing under at high speed . 1 Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted July 15 Share Posted July 15 12 hours ago, h67st said: If you're just going to bobtail or run light, you can install 2024 chambers on a lot of these old trucks. My H model has the SWDL56 (IIRC) rear bogie; it used to have rotochambers next to the frame rail: I "clocked" them one bolt hole to get the chambers below the frame rail. The chambers are very close to the rims because I have 10:00-20 tires; if you are running 22.5 or if you have 22" hubs then this won't be an issue. funny to see those rotochambers- have rebuilt quite a few in the day. 6(?) bolts separate chamber from base; inside a large o-ring and wiper with spring =not a HD maxi spring. outer shell would develop a ring inside and leak. almost positive they aren't legal any more. Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 15 Share Posted July 15 (edited) 3 hours ago, mechohaulic said: one unit for sure which had the service/parking brake set up was an old martin lowbed a customer had. small 12 (1/4) in brake pads . set buttons and drop trailer; brakes were locked, using air to hold them. system lost air =trailer lost parking brake. it used to be dropped on blocks since there weren't any landing gear. driver in hurry backed under before hooking lines , trailer rolled away, which is why going for a CDL =requirement was to hook lines before truck went under trailer. old rule based on old system. many trailers rolled away if backed under first. I made a set of 3ft long with 4 in pipe with 3 in pipe inside having 3 sets of 2 in holes for pin to raise/ lower legs. and yes they bent those backing under at high speed . Oh, that is different, yeah trailers before -121 didn't have parking brakes, only emergency (break a way) brakes. Most vans and flatbeds got spring brakes around 1975 but specialized and heavy haul were exempt and may still be. I thought you were talking about tractors using air for parking. Never heard of or saw that. I've towed many trailers without spring brakes. RGN's multi piece heavy haul stuff etc didn't have any parking brakes. I think they may now need them, but in the 90's they didn't. The newest heavy haul stuff I pulled had an extra air tank and manual valve to release the brakes so they could be "assembled" into hauling configuration from being stacked on the main deck for transport to-from the load/unload points. Std procedure was to back close to the trailer, air it up then pull the red line and back under. Edited July 15 by Geoff Weeks Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 15 Share Posted July 15 (edited) 3 hours ago, mechohaulic said: funny to see those rotochambers- have rebuilt quite a few in the day. 6(?) bolts separate chamber from base; inside a large o-ring and wiper with spring =not a HD maxi spring. outer shell would develop a ring inside and leak. almost positive they aren't legal any more. Wrong! Are legal but cost about 10x what a diaphragm chamber does. They are smaller in diameter for the same "size" and will fit where clamp chambers will not. You see them more on heavy off road equipment than on on-road trucks. Also can be had with spring brakes built in. When spring brakes are in the chamber the spring is in the 1/2 closest to the push rod, and a tube surrounds the push rod and butts up to a large (thick) washer on the push rod, applying the brakes. I almost lost a finger to one of these when searching for an air leak on a bus when the brakes tripped and caught my finger between the tube and washer. The one that got me, was a rotochamber on a Austrian bus (Graff-Stief sp?) , but worked like the Maxi, unless I am mistaken and it was a Maxi? I don't think so, it happened over 40 years ago so my memory could be off. A -30 rotochamber is smaller in diameter than a -30 clamp chamber. Re-reading your post, I think you are confusing old Maxi-brake with roto chambers. Roto chambers don't use O rings, they use a rubber cone kinda like an air bag with out the top and bottom plate. Maxi-brakes had a piston (as did other types of piston spring brake chambers) Maxi's were the ones that couldn't be "caged" in the field like most modern brakes can. easy to mix them as they look somewhat similar. Roto chambers claim to fame is they have an almost constant force over the whole travel. Top to bottom, Maxi, rotor chamber, rotor chamber diaphrgm. Edited July 15 by Geoff Weeks add pic's Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 15 Share Posted July 15 (edited) To get back to the OP problem, I was doing some reading on the exceptions to the spring brake requirements. 393.41 sub parts B and C seam to indicate that spring brakes would not be required if the tractor NEVER towed a trailer, as it pre dates the requirement. The spring brake requirements were only retro-active for "combinations". Which I guess explains why you can see single vehicles (straight trucks) with driveshaft brakes later than when spring brakes were common on tractors. Also mentions the "heavy haul" exception. It does seam to indicate that if you did put smaller cans on to gain spring brakes you would be against the law as now the brakes are not as effective as when the truck was built. Whether that would bring you grief or not, I don't know? Edited July 15 by Geoff Weeks Quote Link to comment Share on other sites More sharing options...
Macman Posted July 15 Author Share Posted July 15 2 hours ago, h67st said: If you're just going to bobtail or run light, you can install 2024 chambers on a lot of these old trucks. My H model has the SWDL56 (IIRC) rear bogie; it used to have rotochambers next to the frame rail: I "clocked" them one bolt hole to get the chambers below the frame rail. The chambers are very close to the rims because I have 10:00-20 tires; if you are running 22.5 or if you have 22" hubs then this won't be an issue. On 7/12/2024 at 7:04 PM, mechohaulic said: in 60's-70's there was a "conversion " set up which had the spring parking brake can mounted inside the frame rail. camshaft housing bolted to rail with hole in frame for camshaft going to outside rail . early set ups had a long 1/2 dia steel rod connecting slack adjuster on axle to cam going through frame. setting parking brake moved the rod which pulled on axle mounted slack. bad idea! rod too long kept braking. change over repair was putting HD cable on replacing 1/2 dia rod. this set up was used on DM's as well with other models.. This truck has a hand operated parking brake lever with a cable running back to the linkage on the front axle. 1 Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 15 Share Posted July 15 1 minute ago, Macman said: This truck has a hand operated parking brake lever with a cable running back to the linkage on the front axle. Yeah, that would still be legal the way I read it, as long as it isn't towing a trailer. So I guess it depends on your plans for the truck? Quote Link to comment Share on other sites More sharing options...
67RModel Posted July 15 Share Posted July 15 (edited) If I recall correctly my B81 had type 20 rotochambers on it. I searched high and low for the 2050 Maxibrake like Geoff attached a picture of. A 2050 Maxibrake is a type 20 rotochamber with a 50 pound per inch spring in the emergency side. It didn't flare out and get larger on the spring chamber. Haldex still listed it as a part number in their catalog but it was discontinued. I could never find any. This was 2 years ago now. and yea my B81 had a handbrake on the drive line with a brake drum and shoes that looked like it belonged on a VW beetle. No way was that thing stopping the truck it was rolling with some momentum. It was 23,000lb unladen Edited July 15 by 67RModel Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 16 Share Posted July 16 Some blokes restoring old petrol IH trucks out here put a RTO 610 RoadRanger in They loose the transmission brake These trucks have hydraulic brakes They make a big band brake up for a transmission brake and fit a maxi can to that These pass inspection okay as I guess they do everything needed A long and large band brake or perhaps a modern disc brake with a maxi can mounted on the tail shaft would achieve the same result Think it was mid 80's when at least 1 trailer axle had to have maxi brakes fitted in Australia Only my low loader doesn't have maxis at all All my other trailers have them on all axles, I started doing this many years ago after a mate said "what happens if you break down on a big hill" This one statement and finding a road train stuck on the Carnavon gorge put the wind up me As every trailer since has had major works done I have put maxis on all axles, bigger air tanks, the lot, brand new airlines front to back I'm not worried about me or my trucks but I would hate to hurt someone by something as simple as maxi brakes Sort of light bulb moment for me and the low loader will get the treatment one day Paul Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 16 Share Posted July 16 Somewhere I read that Heavy Haulers with out maxi's had to have eough chalks carried to hold the rig. We always had dunnage to block the wheels. From what I could find researching on line, the rules I knew are still in effect, Pole trailers and heavy haul under a listed deck height were exempt from the spring brake rule, so Goldhoffer (sp?) platform trailers, and trunnion axle trailers are exempt. Quote Link to comment Share on other sites More sharing options...
h67st Posted July 16 Share Posted July 16 In the old days of trailers using air pressure to hold the single-stage chambers as a parking brake, when we would hook to a trailer with no air and charge the parking gladhand, the parking brake would set momentarily until the trailer tank got enough air in it. A lot of our drivers almost got into trouble thinking that they would stay set but then they released. My dad had some old trucks in the early 70's, he had his mechanic convert them to spring brakes but there was a steep learning curve after that. Me and my dad stopped at a truck stop in 1975 somewhere around Kentucky that had a steep parking lot; we got out and headed up the hill to get lunch. When we got to the building, there was this old guy sweeping the drive and he said, "Mister, your truck's rolling away". My dad ran after it but the trailer jackknifed and thankfully the landing gear leg hit the fuel tank so the cab didn't get smashed. After that my dad made sure to set both buttons when he got out! Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 16 Share Posted July 16 Before maxis were on trailers all the landing legs had wheels on them so when your backing in if the trailer rolled a bit the legs didn't get bent Another thing of the past thats long gone and a lot of drivers today wouldn't even know why older trailers had the landing leg wheels Paul Quote Link to comment Share on other sites More sharing options...
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