Anyone mounted a lift for a heavy motorcycle on the rear of their coach?? They usually have two additional receivers to help support the load, it would be about 1000 lbs 2 feet out from the coach. Bad ideal, works great?? OK for MCI or Prevost but not GMC??
Ken
Oh No!!!! :o ::)
http://www.busconversions.com/bbs/index.php?topic=18363 (http://www.busconversions.com/bbs/index.php?topic=18363)
That thread did not go well. Several posts were removed including the original post that started the thread. However, there is enough left that you can get the idea.
I posted a quick calculation in that thread that you can looks at. That was looking at the loading statically. I am concerned that the dynamic loads could be significantly higher.
People do this, but mostly with S&S that have a full frame.
You are a good enough fabricator and have a good sense of what is correct, that I think you could pull it off. My comments in that thread were aimed at new folks to make sure they think their way through the issue and have some idea of why it might not work on all buses.
Jim
Ken, I am certainly no expert on this, but your Prevost, which I think has a frame, is much more likely to be capable of it than MCI or GM with monoque construction.
I have seen it done on a Prevost. I have a 4106 and I would not say its impossible but I would not recommend it. Too much weight IMO.
I would think that if you can put a 20K hitch on a Prevost, you can put a motorcycle lift. I recall the thread and pictures of the person who changed out the subframe on his Prevost to tow a giant stacker trailer.
Brian
Quote from: rv_safetyman on August 15, 2012, 10:47:55 AM
Oh No!!!! :o ::)
http://www.busconversions.com/bbs/index.php?topic=18363 (http://www.busconversions.com/bbs/index.php?topic=18363)
That thread did not go well. Several posts were removed including the original post that started the thread. However, there is enough left that you can get the idea.
I posted a quick calculation in that thread that you can looks at. That was looking at the loading statically. I am concerned that the dynamic loads could be significantly higher.
People do this, but mostly with S&S that have a full frame.
You are a good enough fabricator and have a good sense of what is correct, that I think you could pull it off. My comments in that thread were aimed at new folks to make sure they think their way through the issue and have some idea of why it might not work on all buses.
Jim
Your words say no no, but you seem to encourage me at the same time. Reminds me of a time when I was much younger.
I agree, sitting still is no problem, F=ma, big bump in the road, 1000 lbs, 2 feet of leverage from the mounts, that's a lot of force.
I should have searched for the old thread, sorry.
Ken
When I bought my bus, I ordered a cheap (read: cheap in every sense of the word) 1000lb motorcycle carrier on amazon and had it shipped to the bus. The seller installed it, I rode to Montana from Seattle and loaded the bike. I ride a Kawasaki Concours, which is an easy 800lbs wet with gear. It was nervewracking and also buckled the loading ramp. We adapted and overcame and got the bike loaded. It seemed a bit unstable so we put a few straps from the corners to the back window. I made it home without incident. The bus drove fine. Note my bus has a frame and is mid engine so the pickup points are there and access isn't as critical to the rear.
However, the bike was extremely sooty when I got home. Like, chimney sweep in Mary Poppins. It looked like a diesel exhaust pipe turned inside out. The bus hadn't been ran in awhile but i think that would always be a issue to some degree. And, there was a rub mark on the back door due to the extra straps.
I am not going to give up on the plan yet. I plan on installing the small car hitch reciever sized things on each back corner of the bus to stabilize and strengthen the carrier. My carrier has provision for a receiver in the back of it. I would like to triangulate and brace that appropriately so I can load the bike and flat tow the wife's jeep and tow both without damaging the jeep, the bus or most importantly the bike. And not have redneck-looking straps etc running all over like before.
I don't think the front carrier as mentioned in the linked thread is completely without merit, but I would want to weigh the bus first. Many buses are right at the limit on the front axles. I would consider it for a vespa or equivalent but realistically not for a hog.
There are tilting ones that would load easier than what I've got and are strong too, but simpler than a lift.
Ken, first of all, I try ***NEVER*** to tell anyone that something can't/shouldn't be done. In my first few years as an engineer, I had a lot of customers prove me wrong :-[. I saw people do things with belt drives that defied any logic, let alone engineering principles.
What I do try to do is present the issues that need to be addressed and let folks make their own decision.
Most folks know that I am always concerned about hanging a big trailer on the back of a bus. I talked at length to a fellow who had a mobile machine shop in a trailer that he towed with a GM bus. He towed the trailer to a whole bunch of vintage sports car races (met him at Watkins Glenn. His trailer was home made and rather large (at least 20 feet). He had all kinds of machining and welding equipment (mill, lathe, etc) in it along with a lot of steel for fabrication. It had to weigh at least 10K. And he towed this behind a GM!!! In my wildest dream, I could not imagine that he had not had a problem. I can't recall the details, but he had a lot of miles on the bus/trailer and had zero problem.
I tell that story so that folks know that I understand it can be done. However, this was done by a fellow who knew structures very well (was clearly not an engineer - and that was good ;D). I could also tell several stories about motorhomes and one Eagle that had frame failures.
Now back to the question that started this post. The thread that I sited was mainly aimed at Eagle buses, but had some thoughts about other buses. The issues with big trailers or a bike rack is two fold. The first issue is, can the suspension handle the load? The second issue is, can the bus structure handle the load?
Concerning the suspension issue, I would start with weighing the bus to determine how each axle is loaded. The axles will have a rated load and that should not be exceeded. Of course, part of that rating is the mechanical limit of the axle and the other part is suspension support limit. My thought on the Eagles is that the support system (Torsilastics) should not be overloaded. Not that they are fragile, but quite a few Eagles are already over GVW and adding that much weight on the rear axle could easily put the Torsilastic over limit. This is especially true since the later Eagles have bogie rather than tag axles.
With your Prevost, I would not worry too much about pushing the air bag limit. Plus you have a tag that probably has more capacity than the bogie on an Eagle (about 10K). I can't address the mechanical capacity of the rear end, but I think you can find that information.
The ability of the structure to handle the load is a tough one. On Eagles, they were never designed to pull a trailer and thus they were not designed for the vertical tongue load. Then the have a SLIGHT propensity to produce FEO2 (r*&t :o). That degrades the strength of the tubing. In my case, I double tubed every tube in the main engine rail structure and added tubing to tie the engine rail structure to the main bulkhead. As a result, I would not be afraid to load the rear structure with up to 1K load, but I would be concerned about the Torsilastics.
As I recall, you did some upgrade of the structure when you did your conversion and you have air bags. If you weigh the bus and the axles seem to have some room to add a load, I would tell you to continue to evaluate the rack design.
Jim
Check speck for tongue weight for 20000lb prevost hitch. should give you your answer. allow for distance from bus. I'm sure your cradle is stronger than stock. Just a idea. DKO just had one installed. Bob
Yep you see the Overbuilt on some Prevost but they all have the 20,000lb receiver and cradle
good luck
Clifford, I have been trying to sort out how long Prevost has been manufacturing their bus with the trailer hitch frame structure. I had been told that they upgraded their structure in more recent times and that the older (?) models did not have that design.
Jim
Jim, our 1997 model had a 10,000# hitch from the factory only 500 # tongue weight I believe around 1992 or 93 was the 1st factory hitch for Prevost from the factory
Some with 80 models say theirs was factory that I doubt looking at the welds lol
A easy way to tell is have the Prevost guys check their parts book it will be there if it was a option for that year model
good luck
If I understand DKO most of the strength was in the cradle? Cost him 5 Grand? maybe to change to pull big trailer.
Ken, I believe you can fab and build a better one than Overbilt I am not impressed with those.
I was watching a guy build one in OR he told me the secret was to have the load past the center of the hitch he was shooting for 1 ft above the center of the hitch I still don't know what difference that would make lol
Quote from: robertglines1 on August 15, 2012, 05:37:42 PM
If I understand DKO most of the strength was in the cradle? Cost him 5 Grand? maybe to change to pull big trailer.
$6500 at Prevost to upgrade engine cradle from 10,000/1,000 to 20,000/2,000. So far so good pulling about 15,000. I have been to western Montana and back with it.
However, I would not do it if I did not need to. The extra weight just "weighs" on my nerves too much.
DKO
I wanna do it, but I just can't feel good about hanging an extra 1000 lbs, 2 feet out, on the rear of my bus. Even though I think I could build the best one ever. I'll pull a trailer or a ½ ton truck with the bike in the truck bed. There's a thread on Prevost Community under the chassis section, read the letter from Prevost. I took a friend out to the Nashville Prevost dealer last night to pickup his coach. I ask the service manger if they had installed the Overbuilt Lifts, he said "yes we've done several of the 20,000 lbs hitches / engine cradles" I said no, I mean the lifts for heavy street bikes that require 2 addition receivers installed on the chassis. He said "no, I've seen them on coaches but I never installed one". He didn't say "we won't install one" but I suspect they won't. Especially after reading the letter from Prevost.
Ken
Ken, I would love to see that letter. Can you give us a link, or can you copy it and send it to me.
Thanks
Jim
Try this
http://prevostcommunity.com/forum/threaddetails.asp?Category=Chassis&ThreadID=607&offset=10 (http://prevostcommunity.com/forum/threaddetails.asp?Category=Chassis&ThreadID=607&offset=10)
the letter is near the bottom.
Ken, thanks for the link. I read through the whole thread and it pretty much goes the same direction that the treads on this board does. Many folks are very concerned about the ability of the structure to handle the static and dynamic loads of a motorcycle rack on the back of motorhomes. Others say they have seen a lot of them on the road with no problem.
One guy talked about risk vs reward. That is really the key.
As I said in this and the other thread, I have first hand knowledge of an Eagle "frame" failure and a motorhome frame failure, plus a couple of second hand stories of similar problems. In the case of the motorhome, I drove with the owner lots of miles to vintage car races. He towed a stacker trailer with two small cars (BMW 2002 and Lotus Elan). These are not heavy cars and we did not carry a ton of tools or support equipment. I can't recall the make of the motorhome (think Monoco), but it was a name brand diesel pusher. It did have a pretty big overhang. I doubt that the coach had 150K miles on it when the original owner sold it to a person I know fairly well. He was towing a trailer down in the SE and lost a transmission. Turns out that the frame cracked and sagged and that put the transmission in a bind. Totaled the transmission and had a lot of damage to the coach.
I know most folks think I am too conservative, but I try to play devil's advocate so that folks know what the worse case issues are.
Jim
I am sure that this is a somewhat crackpot thought, but could it not be possible put some landing gear, maybe spring loaded, beneath the carrier that would keep a substantial amount of the weight off the frame? It would still be easier than using a trailer.
Most of the carriers I have saw are on the Prevost MH chassis design for slides they are a different design than a non slide Prevost chassis hell for strength with the beam on both sides on the slide models I think they would carry one ok maybe not
good luck