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floppydisk35

I can finally afford to make a FWD dragster

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First things first, yes I know it's been about a year since I last logged in, sorry for that. :/

Anyway, last year I kept wanting to do a FWD dragster since last year, but I didn't have the money. No money, no car. Now that I've saved something, I think I can actually come up with something. In general, I have a set of parameters in mind;

a. MUST be completely fwd.

b. hocus pocus of parts up front for steering, transmissible, motors and suspension, and from the middle end to the rear end a plate or two to hold the batteries, rear wheels, servo, and maybe ESC in place. No rear shocks, for added traction.

c. direct belt driven system.

d. touch approximately 90, maybe 100km/h.

e. must not spend more than €4/500.

So, onto my list of boring questions...:(

a. since direct drive seems like a good idea to me, what belts can support such 'tension'? It needs to be pretty short, since the motor will be hanging in front of the front axles - also, the diff will be locked: no need to go round bends, being a dragster.

b. it needs to have a FWD body, and thus I'm thinking of either a Golf Mk.5, or a Civic. Since they fall in the 190mm range, and fat tires will be used for traction up front, the tires would then be pushed in the chassis. Are there any short arms, and shock towers present to accommodate this? If a 200mm width is to be kept, and 2 tires take about 5cm each, only 100mm are left to mount a shock tower, arms, diff, knuckles, steering mechanisms, ... Do such short parts exist?

c. power plant, what's best? I need to get the most out of two 2S LiPo, 3200mah with 20C burst. Both of them will be mounted on at the same time. Also, since not much juice may be pulled from them at the same time, what if (oh, what if, what if!) a capacitor is connected in series with the Lipos for added power at a switch's flick?

Final question..

d. is all this possible?

Next Friday I'll meet with my friend to possibly compile a shopping list, but we obviously need input from other people. :blink:

Thanks in advance, for your kindness! And sorry I haven't visited anywhere recently..!

-Paul. :lol:

EDIT: Forgot to mention that the main chassis and structure will all be custom made and cut, even the motor mounts. :)

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Just wondering... Have you looked at the FF03Pro kit? If you have, could you tell me why it isn't suitable for this FWD dragster project? (other than it being a kit you buy and assemble instead of something you've made and built yourself?) I've often toyed with the idea of making my own chassis aswell (in particular an FR chassis) but I simply keep finding kits to buy. :blink:

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You can probably hit 90-100km/h regularly with an off-the shelf front-drive car and an off-the-shelf modified motor running off 2s.

If you want to build something custom - that's great. My main concern is what tyres you you have in mind, and do believe they will actually grip any better than the narrow racing tyres which are very highly developed. And in what distance do you hope to hit 90-100km/h?

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Just wondering... Have you looked at the FF03Pro kit? If you have, could you tell me why it isn't suitable for this FWD dragster project? (other than it being a kit you buy and assemble instead of something you've made and built yourself?) I've often toyed with the idea of making my own chassis aswell (in particular an FR chassis) but I simply keep finding kits to buy. :blink:

Umm, that is the reason - I want to make something myself. :( Yes, it is easy to slap in a big motor, but then where's the fun? :lol:

You can probably hit 90-100km/h regularly with an off-the shelf front-drive car and an off-the-shelf modified motor running off 2s.

If you want to build something custom - that's great. My main concern is what tyres you you have in mind, and do believe they will actually grip any better than the narrow racing tyres which are very highly developed. And in what distance do you hope to hit 90-100km/h?

Hi, about distance...hmm, make that a 100m. Also, I was thinking of big fat foams for the simple reason of traction - also for high speed stability. Anyway, 90-100km/h was chosen only for modesty. I'll just take it as fast as I can, I guess! :) Still, I found these 1/10 pan cars tires from BSR Racing for 20 bucks. Seems plausible!

Anybody know a good brushless motor accepting 4s? Oh and, do wheels and tires with around 15mm thickness exist?

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make the wheel bigger & the foam as thin as possible.

Thick foams squirm under power; also more chance of chunks flying off.

btw M03 Mini has already hit 100km/h

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make the wheel bigger & the foam as thin as possible.

Thick foams squirm under power; also more chance of chunks flying off.

btw M03 Mini has already hit 100km/h

Whoa that's....that's fast! :P Well, I guess I have to up the stakes, now! Anyway, my friend came over a couple of days ago, and we decided to go crazy on the thing... thus a sketch was drawn!

el4sgg.png

Practically, the motor turns a spur by means of a belt, spur is connected to a (locked) diff, driving the wheels. This means that the motor will be out of the bonnet, blower style. The reason being that for a donor car, we will be using parts from a Thunder Tiger SSK and Tomahawk, apparently. Initially I wanted the motor to be mounted transversely and connected directly via a belt, but since the differential is located halfway between the wheels, the motor was going to be badly offset. Therefore longitudinally mounted it shall be!

Apart from the list of things which might go wrong (belt failing, unaligned gears, etc), what are other drawbacks of such system?

Thanks for reading! :lol:

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Apart from the list of things which might go wrong (belt failing, unaligned gears, etc), what are other drawbacks of such system?

Well, for one thing, you want your drive shafts to be as close to horizontal as you can get them, and if you go and stick a big spur gear on the end of the gearbox you won't be able to do that because you'll need to get clearance between the spur and the chassis. To do that you'll need to raise the gearbox, and to do that will mean increasing the shaft angle.

I'm not sure I understand the reason why you're trying to depart from the usual motor/gearbox/differential approach. It's tried, it's tested and you know it can give you the speeds you need. Plus you have the added tuning options of slipper clutch and adjustable ratios already incorporated into the design. Using a gearbox from an FF chassis doesn't stop you custom making the rest of it.

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Umm, that is the reason - I want to make something myself.

Cool. I thought that might be the reason. Good luck with the project and keep us updated. Breaking 100km/h should be an awesome thing to see.

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Cool. I thought that might be the reason. Good luck with the project and keep us updated. Breaking 100km/h should be an awesome thing to see.

Thanks a lot!

Well, for one thing, you want your drive shafts to be as close to horizontal as you can get them, and if you go and stick a big spur gear on the end of the gearbox you won't be able to do that because you'll need to get clearance between the spur and the chassis. To do that you'll need to raise the gearbox, and to do that will mean increasing the shaft angle.

I'm not sure I understand the reason why you're trying to depart from the usual motor/gearbox/differential approach. It's tried, it's tested and you know it can give you the speeds you need. Plus you have the added tuning options of slipper clutch and adjustable ratios already incorporated into the design. Using a gearbox from an FF chassis doesn't stop you custom making the rest of it.

You are right, using the widespread and well-known method you mentioned is the safest way to go, but i want to have the least amount of mechanical parts, even if that might increase the amount of difficulties in creating that..And yes, that spur will be somewhat angled, together with the motor...

Thanks for your reply - no, really! I appreciate it! :P

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HPI makes 200 mm shells for FWD cars, IIRC.

With regards to your home-made chassis, why place the motor at a 90 degree angle? The torque will cause a load of torque steer, something you want to avoid in a dragster. The motor axle should be parallel to the drive axles.

Using a F1 gearbox is not viable because some minor amount of steering is required, and the axle of the F1 won't permit that. Rear wheel steering would be the only option, a bad idea for a high speed car.

FF-03 could probably be tuned up to go 100 km/h, but perhaps you should consider tracking down a Yokomo YR-F2 (just Google it), which has almost a direct drive transmission...

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HPI makes 200 mm shells for FWD cars, IIRC.

With regards to your home-made chassis, why place the motor at a 90 degree angle? The torque will cause a load of torque steer, something you want to avoid in a dragster. The motor axle should be parallel to the drive axles.

Using a F1 gearbox is not viable because some minor amount of steering is required, and the axle of the F1 won't permit that. Rear wheel steering would be the only option, a bad idea for a high speed car.

FF-03 could probably be tuned up to go 100 km/h, but perhaps you should consider tracking down a Yokomo YR-F2 (just Google it), which has almost a direct drive transmission...

In fact I once had the opportunity to buy one, and the belt is what had hit me most, and the weird shock absorber placements. :P

Anyway, the reason why it is not going to be transversly mounted is because of this;

sgpxy8.png

If the diff is exactly between both wheels and a direct drive system is applied (from motor to diff), the motor has to be offset. Since I guess a heavy 550 motor will be used, this will, I guess, provide more torque steer than the set up I want to apply... On the other hand I can apply the Yokomo's type of transmission, but since I don't want any gears meshing together involved, well...

PS: Next Friday I'll be meeting my friend again. Hope we'll do some progress. Also, I might start the actual chassis design next weekend. ;)

PPS: I know it's bonkers but, I prefer calling it "interesting". ;)

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In fact I once had the opportunity to buy one, and the belt is what had hit me most, and the weird shock absorber placements. :D

Anyway, the reason why it is not going to be transversly mounted is because of this;

sgpxy8.png

If the diff is exactly between both wheels and a direct drive system is applied (from motor to diff), the motor has to be offset. Since I guess a heavy 550 motor will be used, this will, I guess, provide more torque steer than the set up I want to apply... On the other hand I can apply the Yokomo's type of transmission, but since I don't want any gears meshing together involved, well...

PS: Next Friday I'll be meeting my friend again. Hope we'll do some progress. Also, I might start the actual chassis design next weekend. :)

PPS: I know it's bonkers but, I prefer calling it "interesting". :P

The motor can be centred from left to right, no problem. You'll end up with a belt slightly more to one side and one outdrive longer than the other (so the suspension+driveshaft geometry stays symmetrical). Similar things are done with transmissions of 2WD buggies, F1 and Pan cars, the FF03 to name an example that could be counted as a competitor for what you want to make... and many more.

The thing is, things don't necessarily get better by making them different than the stuff already out there. From a performance point of view, even for a dragster, you want a low centre of gravity, so the motor on top of the gearbox would be something you'd try to avoid at all times. Also, more gears and I believe bevel gears in particular will drastically affect the efficiency of the drivetrain.

However, do you really want the car to be better than the stuff already out there? Or does it need to be the car that you designed because you like a certain way it's been put together (like the gearbox)? Many companies or projects strive to reach to an ideal, and often that reflects in their design in a good way (different components and decisions about how they work make sense because they try to reach to that same goal in the best way possible) so perhaps if you make one for your projects and try to maximize that about your car - will that be in the region of performance, the looks, not often or not yet seen mechanisms, or combinations of these? ;)

Also, there's of course much more than the gearbox. Even a dragster needs some kind of setup in terms of weight balance, suspension setup and perhaps even downforce. I'd look at more than just those and try to get as much information from people who have already made a custom FF car or optimized an existing one for drag racing, or make the car as adjustable as you can (Think wheelbase, camber, toe, adjustable wing perhaps, moveable battery position on the car for the weight balance) - if you're looking for maximum speed/performance, that is. Things like this make sure that you can optimize your design from the ground up, or as you go (setup/adjustability).

Anyhow, I'm really looking forward to seeing more of this project! :) It's a very cool idea to make an FF Dragster!

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The motor can be centred from left to right, no problem. You'll end up with a belt slightly more to one side and one outdrive longer than the other (so the suspension+driveshaft geometry stays symmetrical). Similar things are done with transmissions of 2WD buggies, F1 and Pan cars, the FF03 to name an example that could be counted as a competitor for what you want to make... and many more.

In fact, that was what I was originally thinking, to shift the differential to the side! But since I will be lifting off parts from a Thunder Tiger SSK the differential is just, where it is and cannot be moved. To be honest though, I haven't yet checked this. If there exists a possible way of shifting the diff a great deal, I might actually revert back to the old plans. Sorry for not mentioning that in the previous comment. :)

The thing is, things don't necessarily get better by making them different than the stuff already out there. From a performance point of view, even for a dragster, you want a low centre of gravity, so the motor on top of the gearbox would be something you'd try to avoid at all times. Also, more gears and I believe bevel gears in particular will drastically affect the efficiency of the drivetrain.

However, do you really want the car to be better than the stuff already out there? Or does it need to be the car that you designed because you like a certain way it's been put together (like the gearbox)? Many companies or projects strive to reach to an ideal, and often that reflects in their design in a good way (different components and decisions about how they work make sense because they try to reach to that same goal in the best way possible) so perhaps if you make one for your projects and try to maximize that about your car - will that be in the region of performance, the looks, not often or not yet seen mechanisms, or combinations of these? ;)

I don't want to sound like an idiot (but I bet I surely do!), but I don't really want to be better than anything else - this is the first RC I will be building. I haven't even built an RC kit! Well, I used to disassemble half my FF01 after dusty runs...

Anyway, yes I do know the fact that a lower centre of gravity is desirable in EVERY situation, and in this case a 300gram motor sitting on top of a bonnet isn't what you call sensible. About performance, it will all be to how much the motor has to offer rather than how parallel the motor is to the car's axles, and how sensible I've been with the set up. What I want is something that looks weird - not necessarily meaning good. Well, I'm not going to strap fireworks at the back, though...:P Anyway, at the end of the day I want to feel good because I've done something fun. :) Still, to be honest I don't know what bevel gears have to offer, but if they're less efficient than two meshing straight cut gears, I might then opt for the latter option.

Would it be a good idea to use the YR-F2's transmission idea for a dragster? That is, a pinion and a spur, and a belt...

Also, there's of course much more than the gearbox. Even a dragster needs some kind of setup in terms of weight balance, suspension setup and perhaps even downforce. I'd look at more than just those and try to get as much information from people who have already made a custom FF car or optimized an existing one for drag racing, or make the car as adjustable as you can (Think wheelbase, camber, toe, adjustable wing perhaps, moveable battery position on the car for the weight balance) - if you're looking for maximum speed/performance, that is. Things like this make sure that you can optimize your design from the ground up, or as you go (setup/adjustability).

Anyhow, I'm really looking forward to seeing more of this project! ;) It's a very cool idea to make an FF Dragster!

In terms of balance, everything needs to be shoved up to the front as much as possible for added traction, and I guess stability. For suspension, only the front end will have proper suspension, while the rear end will have the wheels fixed directly to the chassis plates. The reason being not to let it squat under acceleration. Also the rear tires need to be thin to avoid friction, but since there will be a loss of grip, I was thinking of downforce by means of a small wing attached to the rear end. And, to be honest I wasn't thinking of creating everything adjustable, but fixed - and the final result will be, it. The idea of making everything adjustable might be a better idea (I feel stupid for not actually thinking of this!)

Anyway, thanks a lot for helping me in this, I reeeaaally appreciate it! :P

Great Vigor already does that

http://www.modelengines.com.au/retail_cata...ref_cat_id=DVHB

Real hard to build anything "unique never-been-done-before" these days huh? :D

Upon seeing that, I immediately remembered how a friend of mine just yesterday said that everything's "innovative" has already been made... I made a bet that she won't find anything similar. Well at least I don't know any front wheel drive dragsters..till now. :(

Anyway, thanks for all the interest shown here! I will keep you all updated.

But for now I'll toggle about the idea of the transmission... :)

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In fact, that was what I was originally thinking, to shift the differential to the side! But since I will be lifting off parts from a Thunder Tiger SSK the differential is just, where it is and cannot be moved.

TT SSK and the other thing u mentioned... they look like 1/8th scale gas buggy / monster truck?

Have u decided exactly what scale you're making?

Or more importantly, have you already got a bodyshell you're building to?

Unless you're planning on custom fabbing the shell too...

Still, to be honest I don't know what bevel gears have to offer, but if they're less efficient than two meshing straight cut gears, I might then opt for the latter option.

bevel gears turn drive thru 90degs

Would it be a good idea to use the YR-F2's transmission idea for a dragster? That is, a pinion and a spur, and a belt...

YR-F2s aren't that common, especially these days - they don't come cheap.

Upon seeing that, I immediately remembered how a friend of mine just yesterday said that everything's "innovative" has already been made... I made a bet that she won't find anything similar. Well at least I don't know any front wheel drive dragsters..till now. :D

fyi fella called Taka cobbled this beast together "FACD-1"

858e04.jpg

1266ea.jpg

he's homemade a motor mount to fit above the gearbox & bulkhead (blue bits are from a TB Evolution IV)

TB Evo IV is one of few touringcars with option of a metal diff ring gear - might be handy for high power.

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That Great Vigor car is 4WD so there's still the chance that you're the first...

They've just mounted the motor that way to make it look like a blower...

Why don't you try and do a rigid front axle with locked a-arms? Just replace the gearbox with a similar set-up as a F10x car...

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