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| TravisBickle |
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TravisBickle
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 Posted: 22:09 - 17 Nov 2020  Post subject: SW Motech engine crash bars PLUS crash bungs??? |
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Hi guys.
Got my delivery today for a number of bolt-on accessories I'd been waiting some time for from Sportsbikeshop (Yay!  ).
Amongst other things are a set of SW Motech engine crash bars.
The bike already had a set of R&G crash bungs installed from before I bought the bike.
I was wondering if using them in conjunction with each other would actually serve any purpose or actually defeat the object of having the crash bars in the first place?
I think I remember reading / hearing somewhere that crash bars are preferred INSTEAD OF crash bungs as if the worst should happen and the bike ends up on its side, the impact would be absorbed over a wider area and because the bars are fixed to the body at 3 points on each side the impact would be distributed across three separate points of the body. Whereas with the crash bungs only being bolted to the frame at 1 point all the impact would be taken at a single area, potentially damaging the frame.
This being the case, would having the crash bungs installed on top of the crash bars actually defeat the object of having the crash bars in the first place? As it looks to me with the crash bungs in place if the bike went down they'd take all or nearly all of the impact anyway (please see photos attached). The crash bungs stick out substantially further than the crash bars.
I've installed them over the top for now but have kept the bolts supplied with the crash bar kit in case you guys recommend taking them off.
So what you think, is it recommended to ditch them or keep them?
https://i.ibb.co/NF0pDSW/20201117-123430.jpg
https://i.ibb.co/CBLQshF/20201117-123421.jpg
https://i.ibb.co/r6wJBtL/20201117-123417.jpg
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| TravisBickle |
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TravisBickle
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| Posted: 03:32 - 19 Nov 2020 Post subject: |
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33 views but no replies?
This makes me sad 
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jeffyjeff
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| grr666 |
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grr666
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| Posted: 09:30 - 19 Nov 2020 Post subject: |
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I'd keep both. Why not? You'll be glad enough of them if they're needed.
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| MarJay |
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MarJay
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Posted: 11:30 - 19 Nov 2020  Post subject: |
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There's a fair amount to unpack here. This is not going to have a simple answer.
My first thought is, if they don't interfere with each other, and they both provide impact protection then why not?
However:
Some people have got anecdotal evidence of R&G (and other makes of ) crash protectors bending and damaging parts of the bike in an impact, or in some cases stripping threads in the engine/frame mountings. I have experienced this with some DHM (Motrax) crash protectors on my old SV650. I had an accident, and ended up with a tiny segment of the frame dented by the edge of the alloy crash protector.
I should add a coda to that, which is that R&G are very experienced with crash protectors, and try to engineer out this type of thing, and make the protectors with this in mind.
They are also engineered to slow the bike in a slide, which the crash bars won't do. So you could end up making things worse by having a combination of the both? It's hard to quantify as it depends on the type of accident you are having!
If it were me I'd leave it. In fact, if it were me I'd have not bothered with the crash bars at all, as I much prefer the R&G protectors.
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another. |
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| TravisBickle |
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TravisBickle
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| Posted: 20:12 - 20 Nov 2020 Post subject: |
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| MarJay wrote: | There's a fair amount to unpack here. This is not going to have a simple answer.
My first thought is, if they don't interfere with each other, and they both provide impact protection then why not?
However:
Some people have got anecdotal evidence of R&G (and other makes of ) crash protectors bending and damaging parts of the bike in an impact, or in some cases stripping threads in the engine/frame mountings. I have experienced this with some DHM (Motrax) crash protectors on my old SV650. I had an accident, and ended up with a tiny segment of the frame dented by the edge of the alloy crash protector.
I should add a coda to that, which is that R&G are very experienced with crash protectors, and try to engineer out this type of thing, and make the protectors with this in mind.
They are also engineered to slow the bike in a slide, which the crash bars won't do. So you could end up making things worse by having a combination of the both? It's hard to quantify as it depends on the type of accident you are having!
If it were me I'd leave it. In fact, if it were me I'd have not bothered with the crash bars at all, as I much prefer the R&G protectors. |
Thanks for the input. I'm guessing if the accident is bad enough / fast enough / high enough impact to bend or break the frame through the crash bungs' existence then I'm guessing you're probably looking at a write-off anyway and any crash bung / crash bar combination isn't going to save the bike? I'm also guessing that crash bungs are there to save some expense on smaller collisions and drops rather than worse prangs likely to write the bike off completely?
The engine bars were partly chosen to give me a mounting point for additional lights so I kinda stick by the decision to stick them on there in any case.
I think I'm going with leaving them both on. I was very grateful the previous owner (West Yorkshire Police) had the foresight to fit the bungs when I had to lay it down at a standstill when I lost my balance trying to do a U-turn on a camber/hill at a weird angle in Sevenoaks once as they took all the weight and didn't damage the fairings or any other part of the bike at all  just a small scuff to the bung and to the bar slider.
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jeffyjeff
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TravisBickle
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sickpup
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MarJay
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MarJay
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sickpup
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| Posted: 10:26 - 27 Nov 2020 Post subject: |
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| MarJay wrote: | It's not about the number of points, |
I'm pretty sure that spreading a load over more than one point lowers the pressure on each individual pressure point.
| MarJay wrote: | but the surface area and the material used. |
Yes and no.
| MarJay wrote: | Crash bars seem to bolt on using very low surface area brackets, |
Which is pretty much irrelevant as long as the mounts are strong enough but not so strong as to transfer damage to the vehicle.
| MarJay wrote: | and the entire force experienced over the width of the entire bar is transferred by a material of equal or greater flexibility to that of the frame, |
Which is what you want as you want the crash bars to take the damage.
| MarJay wrote: | via a very small surface area bracket. |
Which is pretty much irrelevant as long as the mounts are strong enough but not so strong as to transfer damage to the vehicle
| MarJay wrote: | Crash protectors tend to spread the load over a wider surface via a nylon part which is flexible and sacrificial. |
And this bit is completely wrong. The size of the nylon bung is pretty irrelevant except that the longer they are, the more leverage there is and the higher the risk of damage to the mount and the vehicle. The relevant part is what they are mounted to and in the case of most bungs they are held on with a single bolt and all the force is concentrated through that single bolt. Earlier in the thread you said...
| MarJay wrote: | Some people have got anecdotal evidence of R&G (and other makes of ) crash protectors bending and damaging parts of the bike in an impact, or in some cases stripping threads in the engine/frame mountings. I have experienced this with some DHM (Motrax) crash protectors on my old SV650. I had an accident, and ended up with a tiny segment of the frame dented by the edge of the alloy crash protector. |
This tends not to happen with crash bars as the load is spread across multiple points and the bars bend before the mounts do and then the mounts bend before the bike does.
Honda use crash bars on their bikes ,BMW use crash bars on their bikes, Harley use crash bars on their bikes. As crash bars cost more to make than a nylon bung with a bolt through it you have to wonder what the reasoning behind this is if nylon bungs are better.
Car manufacturers use crumple zones to dissipate and absorb energy which is pretty much what crash bars are.
Yes there are differences between how cars get damaged and how bikes get damaged, not many cars fall over but no other modern vehicle uses a form of crash protection that can pass the damage direct to the chassis and expect the vehicle to be usable afterwards |
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MarJay
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| Posted: 11:43 - 27 Nov 2020 Post subject: |
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Classic Sickpup. Press me for reasons on why I happen to hold a particular opinion (which I presented as opinion) and then shoot down those reasons. You really do like setting traps don't you?
I happen to disagree. Having a large surface area go down to one or two small surface area points concentrates the force imparted on the large surface area down to the small. Hence why high heels sink in mud but normal shoes don't.
Yes there are issues with torsional forces on a crash bung, but that only really occurs if the bungs are badly designed or catch on an obstacle like a kerb or other road furniture. The bungs that caused the issue for me on my SV had a dome shape on the end, which meant the contact point on the floor was smaller than a wide bung would be. The spacer on the bung was steel, and the bolt used was not a hardened one, which meant that it was designed to bend and designed to press the steel spacer into the soft alloy of the frame. It was not an R&G bung, and wasn't really designed as much as it was thrown together by Motrax (not the last word in quality!).
R&G bungs do actually get designed with some of the factors in a crash in mind, and usually place a fairly wide spacer made of nylon against the frame. The bolt itself is as short as it can be and still hold on the bung, meaning the force is mostly placed on the bung rather than the bolt.
But to be honest, all of this is irrelevant as this was expressed as a personal opinion rather than fact. It's impossible to know which are better because you would need to deliberately crash bikes in a repeatable way to show which is better. You also make the point that manufacturers supply engine bars. It's also true to say that the manufacturer has a vested interest in selling you parts after you have a mishap.
The main reason I happen to buy R&G bungs for all of my bikes is that in the event of a low speed drop, they protect engine cases and bodywork. I've had infinitely more low speed drops than high speed, and I think that the R&G bungs provide a good compromise between the two. My track bike has engine case protectors but no crash bungs. Take from that what you will.
But to reiterate I can recommend whatever I want to recommend, but it is opinion, and I have explicitly stated it's opinion, and anyone who says they know for a fact that you're better off having bungs, not having bungs, having bungs and bars or whatever is talking out of the top of their head, because it depends on so many factors, not least of which the type of accident you end up having.
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sickpup
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| Posted: 13:44 - 27 Nov 2020 Post subject: |
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Classic Marjay, expresses an opinion with an air of authority as if it is fact and not opinion and then gets pissy when pulled up on it.
I also didn't say that certain manufacturers supply engine bars, I wasn't aware that any do. I actually said they fit crash guards such as on the 650 and 700 Deauvilles, the Pan Europeans, The Police spec BMW's and various Harley's that had anti-roll over bars and often bars in the lower fairings.
To suggest they use crash bars instead of bungs as they have a vested interest in you damaging your bike is a pretty pathetic and childish argument. |
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Tdibs
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MarJay
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| TravisBickle |
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TravisBickle
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| Posted: 17:53 - 28 Nov 2020 Post subject: |
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Oh my! What have I started here?
Could end up in the flame wars section at this rate 
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Old Thread Alert!
The last post was made 5 years, 303 days ago. Instead of replying here, would creating a new thread be more useful? |
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